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160 Background: Darolutamide is androgen-receptor (AR) inhibitor with low blood–brain barrier penetration and limited potential for clinically relevant drug–drug interactions. Darolutamide has been shown to increase overall survival in combination with androgen deprivation therapy (ADT) in patients with newly diagnosed metastatic hormone sensitive prostate cancer (PC) and, in combination with docetaxel, in men with non-metastatic castration resistant PC. This phase 2 study assessed the efficacy and safety of DARO as a monotherapy without ADT in patients with non-castrate testosterone (T) levels (≥230 ng/dL). Methods: This was a 24-wk, open-label, randomized study of patients with hormone-naïve, histologically confirmed prostate cancer (all stages, with a max of 4 metastatic lesions) requiring hormonal treatment, an ECOG PS score of 0, and a life expectancy >1 y. All patients received DARO 600 mg bid or commercially available LHRH analogue. The primary endpoint is PSA response defined as a ≥ 80% decline at week 24 relative to baseline, in the DARO study arm. The ADT arm is used as an internal control. Secondary endpoints included changes in T levels, safety/tolerability, and quality of life. Results: Among 61 men enrolled, the median (range) age was 72 y (53-86y); 49.2% had metastases; 14.8% and 62.3% had undergone prostatectomy or radiotherapy before study entry. The median (range) of PSA at baseline was 8.9 ng/mL (2.2-333.8). In the DARO arm, the evaluable population with available PSA values at baseline and week 24 consisted of 21 patients. The PSA response rate (>80% PSA decline at wk 24) was 100%, with a median (range) decrease of -99.6% (-94.3, -100) at wk 24 in the DARO arm. Serum T levels increased by a median (range) of 43.4% (5.7-144.0) at wk 24, compared with baseline. In the DARO arm, 45.2% of men reported drug-related AEs (mostly Grade 1 or 2). Most frequent treatment-emergent AEs included gynaecomastia (19.4%), fatigue (12.9%), and hot flush (12.9%). 3.1% of men experienced SAEs, none of which were drug related. HR-QoL measures and ADT arm results will be presented as internal reference. Conclusions: DARO monotherapy (600 mg bid) was associated with significant PSA response in nearly all men with hormone-naïve prostate cancer. Testosterone level changes and most common AEs (gynecomastica, fatigue and hot flush) were consistent with potent AR inhibition. Clinical trial information: NCT02972060 .

15 Background: In ARASENS (NCT02799602), DARO plus ADT and DOC significantly reduced the risk of death by 32.5% (HR 0.68; 95% CI: 0.57–0.80; P

20 Background: Metastatic castration-sensitive prostate cancer (mCSPC) primarily affects older men (OM). In this post-hoc analysis we investigated the safety and efficacy of abiraterone acetate + prednisone (AAP) in older (≥ 70 years) and younger (< 70 years) patients in PEACE-1. Methods: Men with de novo mCSPC were allocated to standard of care (SOC), SOC + AAP, SOC + radiotherapy (RXT), or SOC + AAP + RXT in this 2x2 design phase 3 trial. SOC was initially androgen deprivation therapy (ADT) alone, then from Oct 2015 onwards, the use of docetaxel (D) was authorized as part of SOC (at the investigator’s discretion until 2017, then, following the publication of LATITUDE and STAMPEDE trials, accrual was restricted to men receiving ADT+ D). Efficacy and safety in OM included in PEACE-1 were analyzed with the same methods used in the overall trial (Lancet 2022; 399: 1695-1707). Results: A total of 741 younger men (YM) (63%) and 431 OM (37%) were randomized. OM presented with more altered PS (ECOG 1-2) (36% vs 26% p=0.0003) and less frequent use of docetaxel (D) as part of SOC (66% vs 51% p

148 Background: In ARASENS (NCT02799602), DARO in combination with ADT and DOC significantly reduced the risk of death by 32.5% (HR 0.68; 95% CI 0.57–0.80; P2 q21d for 6 cycles). The effect of DARO on DOC PK was assessed by noncompartmental analysis from the first 25 patients with dense PK data and by population PK (PopPK) for all patients. DARO PK from ARASENS were compared with PK data from ARAMIS (NCT02200614; without DOC) to evaluate the impact of DOC on DARO PK. Results: Of 1306 randomized patients, 1305 were included in the full analysis set (DARO, n=651; PBO, n=654). The median treatment duration was longer with DARO vs PBO (41.0 vs 16.7 months) and more DARO-treated patients (45.9% vs 19.1%) were still receiving treatment at primary analysis cutoff (Oct 25, 2021). Almost all patients completed 6 cycles of DOC in both groups (DARO, 87.6%; PBO, 85.5%). The proportion of patients requiring DOC dose modification (interrupted/delayed or reduced) was similar between groups (DARO, 60.0%; PBO, 62.9%). TEAEs led to discontinuation/reduction of DOC in 8.0%/19.9% of DARO patients and 10.3%/19.5% of PBO patients. PopPK analysis indicated that DOC PK in ARASENS was generally consistent with that in the literature. A slight numeric increase in DOC exposure was observed in the DARO + DOC + ADT arm, with 15% higher maximum plasma concentration (geometric mean, 1.93 vs 1.68 µg/mL) and 6% higher area under the concentration-time curve (AUC0-tlast within an 8-hour sampling interval, 2.10 vs 1.99 µg·h/mL) vs PBO + DOC + ADT. This small numeric increase is likely not clinically relevant given the variability in DOC exposure (coefficient of variation, 23%–54%). PK meta-analysis of ARASENS and, which considered patients’ intrinsic characteristics as covariates (eg, age, body weight, region), indicated a 10% lower AUC0-12ss of DARO in patients receiving DOC vs those not receiving DOC, which is not considered clinically relevant. Conclusions: The combination of DARO + DOC + ADT increases overall survival with similar overall incidence of TEAEs and no observed drug-drug interactions between DARO and DOC. DARO can be effectively and safely administered with DOC in patients with mHSPC without clinically relevant changes in PK of DARO or DOC. Clinical trial information: NCT02799602 .

Background Fatigue is a multifactorial symptom commonly reported by patients with prostate cancer as a result of disease and treatment. This study assesses the impact enzalutamide has on patient-reported fatigue (“fatigue”) by using patient-reported outcomes from four pivotal, placebo-controlled trials of enzalutamide (ARCHES (NCT02677896), PROSPER (NCT02003924), PREVAIL (NCT01212991), and AFFIRM (NCT00974311)). Methods Fatigue was assessed in the individual studies using the Functional Assessment of Cancer Therapy–Prostate item GP1 at baseline, weeks 13 or 17, and every 12 weeks until disease progression. Longitudinal changes were assessed using mean scores and mixed-model repeated measures. Results The fatigue rates at baseline were higher in patients with later-stage disease (metastatic and/or castration-resistant prostate cancer (CRPC)) and among patients who had already received prior treatment lines; rates ranged between 58% in PROSPER (nonmetastatic CRPC) and 86% in AFFIRM (post-docetaxel metastatic CRPC). Irrespective of disease state, initiation of enzalutamide or placebo resulted in an early increase of fatigue (by weeks 13 or 17), with fatigue levels stabilizing thereafter. At last assessment, ≥55% of patients reported fatigue improvement or stabilization in all trials compared to baseline. More patients reported fatigue worsening by ≥1 or ≥2 units with enzalutamide plus androgen deprivation therapy (ADT) than with placebo plus ADT in ARCHES, PROSPER, and PREVAIL, but the between-group difference was Conclusions The levels of fatigue were greater in mCRPC and lower in earlier states of disease. In all trials, patients reported a small increase in fatigue for the first 13–17 weeks after starting enzalutamide or placebo, with slightly greater fatigue with enzalutamide in all studies except AFFIRM, but fatigue stabilized or improved thereafter. This suggests a role for clinical management of fatigue to help patients cope early in treatment.

e18757 Background: Treatment options for patients with HSPC have broadened, and data regarding patient preferences for therapies can aid in therapeutic decision-making. This study evaluated the impact of attributes associated with therapies for US patients with locally advanced prostate cancer (LAPC) or metastatic HSPC (mHSPC) from the perspective of patient preferences. Methods: An online discrete choice experiment (DCE) was developed for patients with LAPC or mHSPC. The DCE included 12 questions designed to systematically require tradeoffs between treatment attributes of efficacy (5-year overall survival [OS]), tolerability (fatigue, skin rash, neurotoxicity, and common chemotherapy-related toxicity), and convenience (administration factors [route, frequency, and setting], concomitant use of steroids, and monitoring requirements). Respondents could choose androgen deprivation therapy (ADT) alone or with hypothetical therapies that improved 5-year OS but had additional adverse events (AEs). Attribute-specific importance weights measuring their relative impact on treatment choices were estimated using a mixed-logit model, which also controlled for heterogeneity in preferences. Results: From September 3 to October 14, 2021, 82 respondents (mean age 61 years) completed the survey (LAPC, n = 40; mHSPC, n = 42), with 61 (74.4%) receiving ADT at the time of the survey. Respondents reported treatment efficacy (36% [95% confidence interval (CI) 22, 49]) as the most important aspect of treatment choice, followed by changes in chemotherapy-related toxicity (13% [95% CI 3, 22]) and the need for concomitant steroid use (12% [95% CI 5, 19]). Respondents considered monitoring requirements (8% [95% CI 5, 19]) to be more important than fatigue (5% [95% CI 2, 13]). Administration factors were comparable in importance to therapy AEs (Table). Respondents preferred, by at least 10 percentage points, adding therapies to ADT that could improve 5-year OS, at the detriment of additional AEs. Conclusions: After efficacy, convenience was considered to impact treatment choices at a rate comparable to tolerability issues, potentially influenced by perceived COVID-19 exposure risks. Patients with LAPC and mHSPC prioritize efficacy despite the detriment of additional AEs.[Table: see text]

5041 Background: Ra-223 extends OS in pts with mCRPC. Predictive markers of response to Ra-223 are needed to help select pts who would benefit most from Ra-223 therapy. The ALSYMPCA study suggested a correlation between ALP decline and longer OS. Here, we evaluated whether ALP decline is associated with OS in the global real-world REASSURE study. Methods: Pts treated with Ra-223 were grouped by baseline ALP ≤147 U/L vs >147 U/L and any ALP decline vs no decline at week 12 from the first Ra-223 dose. The 147 U/L cut-off was selected based on the highest upper limit of normal for ALP from literature. Pts with a trend of decreasing ALP at closest value to week 12 between weeks 8 and 16 were included in the any decline group. Association of ALP decline with OS was assessed in the ≤147 U/L and >147 U/L groups separately. Median OS is provided with an unadjusted hazard ratio (HR) (95% confidence interval [CI]). Multivariate Cox models provided adjusted HRs (95% CI) for the association of ALP decline with OS. Some baseline covariates were not included in the models due to missing data. Results: 785 of 1465 pts had baseline ALP measurements, of whom 779 had week 12 ALP measurements: 443 had ≤147 U/L and 336 >147 U/L. In the ≤147 U/L group, median OS was 23.0 months (m) (95% CI 20.9–25.7) in pts with ALP decline (n=329) and 16.4 m (95% CI 14.1–20.4) in pts with no decline (n=114). In the >147 U/L group, median OS was 12.9 m (95% CI 11.7–14.3) in pts with ALP decline (n=295) and 8.1 m (95% CI 5.6–10.3) in pts with no decline (n=41). Comparison of unadjusted and adjusted HRs is shown in the Table. Conclusions: Pts with an ALP decline in first 12 weeks of Ra-223 treatment had longer OS. The effect of other baseline variables, including age, PSA, Hgb and prior treatments, provided adjustment but did not change this outcome. [Table: see text]

5078 Background: Reductions in PSA level have been associated with improved OS in patients (pts) with mHSPC. In ARASENS (NCT02799602), darolutamide (DARO) + androgen-deprivation therapy (ADT) in combination with docetaxel significantly reduced the risk of death by 32.5% (hazard ratio [HR] 0.675; 95% confidence interval [CI] 0.568–0.801; P< 0.0001) vs ADT + docetaxel in pts with mHSPC. We report the association between PSA response and OS from ARASENS. Methods: Pts with mHSPC were randomized 1:1 to DARO 600 mg twice daily or matching PBO + ADT and docetaxel. Serum PSA was measured at screening and every 12 weeks. Exploratory analyses included time to PSA progression (≥25% increase from PSA nadir [lowest or at study entry] and PSA increase ≥2 ng/mL ≥12 weeks from nadir [both confirmed by a second value ≥3 weeks later]) and undetectable PSA (< 0.2 ng/mL for 2 samples ≥3 weeks apart) at 24, 36, and 52 weeks and any time during treatment. Comparisons between treatment groups were performed using the Cochran-Mantel Haenszel test stratified by randomization stratification factors (metastatic spread according to TNM classification and alkaline phosphatase levels at study entry). Post hoc landmark analyses evaluated the association between undetectable PSA at weeks 24 and 36 and OS for the overall population. Results: Of 1306 randomized pts, 1305 were included in the full analysis set (DARO 651; PBO 654), both with ADT and docetaxel. Median (range) PSA levels at study entry were 30.3 (0.0–9219.0) and 24.2 (0.0–11,947.0) ng/mL, respectively. DARO significantly prolonged time to PSA progression (HR 0.255; 95% CI 0.208–0.313; P< 0.0001). Undetectable PSA was achieved in more pts receiving DARO (48.7%) vs PBO (23.9%) at 24 weeks, and the rate continued to increase at 36 and 52 weeks in the DARO group to 57.1% and 60.2%, respectively, vs minimal change in the PBO group (25.1% and 26.1%). Undetectable PSA levels at any time were achieved in 67.3% in the DARO group and 28.6% in the PBO group. A treatment difference in undetectable PSA based on non-overlapping 95% CIs was observed at all time points. For the overall population, OS was improved for pts who achieved undetectable PSA levels vs those who did not at 24 weeks (HR 0.398; 95% CI 0.321–0.493) and 36 weeks (HR 0.351; 95% CI 0.284–0.434). Additional baseline and safety data by PSA level will be reported. Conclusions: The combination of DARO + ADT and docetaxel significantly prolonged the time to PSA progression and more pts receiving DARO vs PBO achieved undetectable PSA levels, reflecting strong PSA response over time. In pts with mHSPC, achievement of undetectable PSA at 24 and 36 weeks was associated with improved OS, with risk of death reduced by 60% and 65%, respectively, vs those who did not achieve undetectable PSA at 24 and 36 weeks. Clinical trial information: NCT02799602.

5084 Background: Current management of HRLPC includes long-term ADT with primary RT. Despite definitive primary treatment, these pts have a high risk of metastasis and death. The phase 3 ATLAS study (NCT02531516) is investigating whether treatment intensification with the addition of APA to neoadjuvant and adjuvant treatment with gonadotropin-releasing hormone agonist (GnRHa) and external beam radiation therapy (EBRT) will improve metastasis-free survival (MFS) in high-risk pts. Here we describe (1) the distribution of baseline characteristics in this high-risk pt population and (2) the application of different RT regimens reflecting recent international guidelines and clinical practice changes for pts with HRLPC. Methods: Eligible HRLPC pts (Gleason score [GS] ≥ 8 or 7 and prostate-specific antigen [PSA] ≥ 20 ng/mL and stage ≥ cT2c), with ECOG PS 0/1 and Charlson Comorbidity Index (CCI) ≤ 3 are stratified by GS, pelvic nodal status, use of brachytherapy boost, and region; pts are randomized 1:1 to APA or PBO plus GnRHa for 30 (28-d) treatment cycles. Study treatment is applied neoadjuvant/concurrent to RT with APA 240 mg/d vs bicalutamide 50 mg/d for 4 cycles; another 26 cycles are completed adjuvantly after RT with APA 240 mg/d vs PBO. Primary end point is MFS (time from randomization to first distant metastasis on CT/MRI/bone scan by independent central review blinded to treatment or death from any cause). Imaging is conducted at baseline and q6m from biochemical failure until MFS. The protocol has been amended to include PET imaging (PSMA, fluciclovine, or choline). Results: Pts (N = 1503) were randomized at 266 sites in 24 countries in North America, Latin America, Europe, and Asia. The study is fully enrolled, but ongoing. Baseline characteristics for the total population: median age, 67 yrs; ECOG PS 0/1; 89%/11%; tumor classification at study entry: high-risk, 66%/very high–risk, 34%; median PSA, 6.3 ng/mL; cT2, 44%/cT3, 50%; cN1, 13%. In 90% of ATLAS pts, RT used was standard EBRT to prostate/pelvis over 6-8 weeks (cumulative 78-81 Gy); in 10%, recent hypofractionation schedules (per CHHiP or NRG/RTOG 0415) were applied (20x3 Gy/d or 28x2.5 Gy/d). 5.6% of pts had EBRT combined with brachytherapy (per ASCENDE-RT). Conclusions: Baseline characteristics of the ATLAS study population are reflective of pts with high- and very high–risk features and pelvic nodal involvement undergoing primary RT in clinical practice. The RT schedules applied reflect recent evidence and guideline changes for the use of hypofractionation in this pt population. ATLAS is an example of how RT can be included in phase 3 trials of HRLPC, in combination with next-generation androgen receptor inhibitors (eg, APA). Clinical trial information: NCT02531516.

13 Background: Darolutamide (DARO) is a structurally distinct and highly potent androgen receptor inhibitor that demonstrated improved overall survival (OS) and metastasis-free survival vs placebo (PBO) and a low incidence of treatment-emergent adverse events (TEAEs) in patients (pts) with nonmetastatic castration-resistant prostate cancer (CRPC). We investigated whether DARO in combination with standard androgen-deprivation therapy (ADT) + docetaxel would increase OS in pts with metastatic hormone-sensitive prostate cancer (mHSPC) in the ARASENS study (NCT02799602). Methods: This international, double-blind, phase 3 study enrolled pts with mHSPC and ECOG PS 0/1 who were randomized 1:1 to DARO 600 mg twice daily or matching PBO in addition to ADT + docetaxel. Randomization was stratified by extent of disease according to TNM (M1a vs M1b vs M1c) and alkaline phosphatase levels ( < vs ≥ upper limit of normal). The primary endpoint was OS. Secondary efficacy endpoints included time to CRPC, time to pain progression, time to first symptomatic skeletal event (SSE), and time to initiation of subsequent systemic antineoplastic therapies. Safety was also assessed. Results: From Nov 2016 to June 2018, 1306 pts were randomized, 651 to DARO and 655 to PBO, in combination with ADT + docetaxel. Median age was 67 y in both arms. At the primary data cutoff (Oct 25, 2021), DARO significantly decreased the risk of death by 32.5% vs PBO (HR 0.675, 95% CI 0.568–0.801; P < 0.0001). The significant improvement in OS was observed even though substantially more pts received subsequent life-prolonging systemic antineoplastic therapy in the PBO arm (75.6%) vs the DARO arm (56.8%). The significant OS benefit was consistent across prespecified subgroups. In addition, DARO significantly delayed time to CRPC versus PBO (HR 0.357, 95% CI 0.302–0.421; P < 0.0001). Time to pain progression was also significantly longer with DARO vs PBO (HR, 0.792, 95% CI 0.660–0.950; P= 0.0058), as were time to first SSE and time to initiation of subsequent systemic antineoplastic therapy. TEAEs were similar between treatment arms, and the incidences of the most common TEAEs (≥10%) were highest during the overlapping docetaxel treatment period for both arms, with grade 3/4 TEAEs of 66.1% for DARO and 63.5%for PBO, mainly due to neutropenia (33.7% vs 34.2%, respectively). TEAEs led to treatment discontinuation in 13.5% of pts in the DARO arm and 10.6% of pts in the PBO arm. Conclusions: In pts with mHSPC, early treatment combining DARO with ADT + docetaxel significantly increased OS and improved key secondary endpoints vs ADT + docetaxel alone. The incidence of TEAEs was similar in the two treatment arms. Clinical trial information: NCT02799602.

IMPORTANCE Both α-emitting and β-emitting bone-targeted radioisotopes (RIs) have been developed to treat men with metastatic castration-resistant prostate cancer (CRPC). Only 1 phase 3 randomized clinical trial has demonstrated an overall survival (OS) benefit from an α-emitting RI, radium 223 (223Ra), vs standard of care. Yet no head-to-head comparison has been done between α-emitting and β-emitting RIs. OBJECTIVE To assess OS in men with bone metastases from CRPC treated with bone-targeted RIs and to compare the effects of α-emitting RIs with β-emitting RIs. DATA SOURCES PubMed, Cochrane Library, ClinicalTrials.gov, and meeting proceedings between January 1993 and June 2013 were reviewed. Key terms included randomized trials, radioisotopes, radiopharmaceuticals, and prostate cancer. Data were collected, checked, and analyzed from February 2017 to October 2018. STUDY SELECTION Selected trials included patients with prostate cancer, recruited more than 50 patients from January 1993 to June 2013, compared RI use with no RI use (placebo, external radiotherapy, or chemotherapy), and were randomized. Patients were diagnosed with histologically proven prostate cancer and disease progression after both surgical or chemical castration and have evidence of bone metastasis. Nine randomized clinical trials were identified as eligible, but 3 were excluded for insufficient data. DATA EXTRACTION AND SYNTHESIS Individual patient datawere requested for each eligible trial, and all data were checked with a standard procedure. The log-rank test stratified by trial was used to estimate hazard ratios (HRs), and a similar fixed-effects (FE) model was used to estimate odds ratios (ORs). The between-trial heterogeneity of treatment effects was evaluated by Cochran test and I2 and was accounted by a random-effects (RE) model. MAIN OUTCOMES AND MEASURES Overall survival; secondary outcomeswere symptomatic skeletal event (SSE)–free survival and adverse events. RESULTS Based on 6 randomized clinical trials including 2081 patients, RI use was significantly associated with OS compared with no RI use (HR, 0.86; 95%CI, 0.77-0.95; P = .004) with high heterogeneity (χ2 5 = 24.46; P < .001; I2 = 80%), but this association disappeared when using an RE model (HR, 0.80; 95%CI, 0.61-1.06; P = .12; τ2 = 0.08). The heterogeneity is explained both by the type of RI and by the inclusion of 2 outlier trials that included 275 patients; the OS benefit was significantly higher with the α-emitting RI 223Ra (HR, 0.70; 95% CI, 0.58-0.83) but not significant with the β-emitting RI strontium-89 (HR, 0.96; 95%CI, 0.84-1.10) (P for interaction = .004). Excluding the outlier trials led to an overall HR of 0.82 (95%CI, 0.73-0.92; P < .001) (between-trial heterogeneity: χ2 3 = 6.51; P = .09; I2 = 54%) using an FE model and an HR of 0.80 (95%CI, 0.65-0.99; P = .04; τ2 = 0.02) using an RE model. The HR for SSE-free survival was 0.81 (95%CI, 0.69-0.93; P = .004) (between-trial heterogeneity: χ2 3 = 6.71; P = .08; I2 = 55%) when using an FE model and was 0.76 (95%CI, 0.58-1.01; P = .06; τ2 = 0.04) when using an RE model. There were more hematological toxic effects with RI use compared with no RI use (OR, 1.48; 95%CI, 1.17-1.88; P = .001). CONCLUSIONS AND RELEVANCE In metastatic CRPC, a significant improvement of OS and SSE-free survival was obtained with bone-targeted α-emitting but not β-emitting RIs. Caution is necessary for generalizability of these results, given the between-trial heterogeneity.

5002 Background: The randomized phase III EORTC-1333-GUCG (NCT02194842) trial compares enzalutamide vs. a combination of Radium 223 and enzalutamide in asymptomatic or mildly symptomatic metastatic castration resistant prostate cancer (mCRPC) patients. The premature unblinding of ERA223 (NCT02043678) in Nov 2017 due to a significant increase in the rate of fractures in the combination of abiraterone and Ra223 arm led to the implementation of the mandatory use of bone protecting agents (BPA) in the EORTC-1333-GUCG trial. Skeletal fractures, pathological or not, are a frequent and underestimated adverse event of systemic treatment of advanced prostate cancer. Whether this mandated use of BPA (zoledronic acid or denosumab) would mitigate the risk of fractures in this patient population was unclear. An early safety analysis (Tombal, ASCO, 2019) suggested that the risk of fractures was well controlled in both arms when patients receive BPA. We present here an updated analysis of fracture incidence with longer follow-up. Methods: As of 28/01/2021, a total of 253 patients (134 after making BPA mandatory) were randomized between enzalutamide/Ra223 and enzalutamide. The fracture rate was estimated with the cumulative incidence method in the safety population of 237 (122 after making BPA mandatory) treated patients. Death in absence of fracture was analyzed as competing risk and censoring was applied at last follow-up. Results: Overall, 69.5% of enzalutamide/Ra223 patients (95.2% after making BPA mandatory) and 73.1% of enzalutamide patients (95% after making BPA mandatory) received BPA on treatment: 13.6% in the enzalutamide/Ra223 arm and 21.8% in the enzalutamide arm did not use BPA at registration, but started during protocol treatment and 55.9% and 51.3% respectively, received BPA since entry. At 36.7 months median follow-up in patients without BPA and 23.1 months median follow-up in patients receiving BPA, a total of 39 patients reported a fracture. Among them, 30 patients (20 in enzalutamide/Ra223 arm) did not receive BPA and 9 (4 in the enzalutamide/Ra223 arm) received BPA (see table). Conclusions: The updated safety analysis confirms the early fracture rate results. In the absence of BPA, the risk of fracture is increased when RA223 is added to enzalutamide. Strikingly, in both arms, the risk remains almost abolished by a preventive continuous administration of BPA, thus stressing the importance of complying to international recommendations in terms of giving BPA to mCRPC patients. This study is sponsored by EORTC and supported by Bayer and Astellas. Clinical trial information: NCT02194842. [Table: see text]

5000 Background: Historically, androgen deprivation therapy (ADT) was the standard of care (SOC) for men with mCSPC. Since 2015, combining ADT with either docetaxel, novel hormonal therapies, or radiotherapy to the primary tumor (RXT) (for those with low burden metastases) was shown to improve overall survival (OS) and thus has become the new SOC. It is unknown whether combining these new treatments on top of ADT further increments outcomes. Methods: Men with de novo mCSPC were randomized to SOC, SOC + abiraterone acetate-prednisone (abiraterone), SOC + RXT, or SOC + abiraterone + RXT. SOC was initially ADT alone, then from Oct 2015 onwards the use of docetaxel was authorized as part of SOC (at the investigator’s discretion until 2017, then, following the publication of the LATITUDE and STAMPEDE trials, accrual was restricted to men receiving ADT+docetaxel). The trial has two co-primary endpoints of radiographic progression-free survival (rPFS) and OS with type I error of 0.1% and 4.9%, respectively. The required number of rPFS events to achieve 80% power has been reached for the abiraterone question (not yet for the RXT question). The interaction between abiraterone and RXT was first tested using a Cox model adjusted for stratification factors (performance status, type of castration, metastatic burden, and when applicable, docetaxel). A hierarchical testing was used to test the effect of abiraterone: overall population, then ADT+docetaxel population. Results: From Nov 2013 to Dec 2018, 1173 men were enrolled (SOC was ADT+docetaxel in 710 pts and ADT alone in 463 pts), median age 67y (IQR: 60-72), high volume 57%, low volume 43%. The median follow-up is 3.5y. No interaction was detected between the effect of abiraterone and that of RXT (p = 0.64), allowing to pool abiraterone arms for comparisons. rPFS was significantly improved in the abiraterone arm in the overall population (HR: 0.54 (0.46-0.64), p < 0.0001; medians: 2.2 vs 4.5 years) and in the ADT+docetaxel population: (HR: 0.50 (0.40-0.62), p < 0.0001; medians: 2.0 vs 4.5 years). bPFS (PFS including PSA progression as an event) also significantly favored abiraterone in the overall population (HR: 0.40 (0.35-0.47), p < 0.0001; medians: 1.5 vs 3.8 years) and in the ADT+docetaxel population (HR: 0.38 (0.31-0.47), p < 0.0001; medians: 1.5 vs 3.2 years). OS is maturing. Grade 3-4 adverse events reported in > 5% of pts within the first 6 months in the ADT+docetaxel population included neutropenic fever (4.5% vs 5.4%), liver toxicity (19.7% vs 13%), and hypertension (12.2% vs 8.6%) in the abiraterone and control arms, respectively. Conclusion: Adding abiraterone to ADT + docetaxel significantly improves rPFS in men with de novo metastatic prostate cancer, with about 2.5 years of absolute benefit in medians, and no meaningful additional short-term toxicity. Clinical trial information: NCT01957436.

5075 Background: In the phase 3 HERO study, the oral GnRH receptor antagonist relugolix demonstrated sustained testosterone suppression superior to that of leuprolide and a comparative 54% decrease in risk of major adverse cardiovascular events. Relugolix was recently approved for use in the US for the treatment of adult patients with advanced prostate cancer. Here, we further characterize the impact of age on the use of relugolix in advanced prostate cancer from the HERO study. Methods: The HERO study was a randomized, open-label, parallel group study evaluating relugolix in men with advanced prostate cancer. Overall, 934 men with advanced prostate cancer underwent 2:1 randomization to receive relugolix 120 mg orally once daily after a single loading dose of 360 mg or leuprolide 3-month injections for 48 weeks. Subgroups analyzed by age were 75 years. Assessments analyzed included sustained testosterone suppression to castrate levels (75 years of age. Across all age subgroups, point estimates for sustained castration rates through 48 weeks for relugolix patients were consistent with the overall estimate of relugolix sustained castration rate observed in the overall population. Differences in sustained castrations rates at week 48 between relugolix and leuprolide groups were similar regardless of the age subgroup (table). The likelihood of testosterone recovery at 90 days after completion of treatment was higher in the relugolix group versus the leuprolide group in all age subgroups: 75 years (40.7% vs 0%). No clinically relevant differences were noted in the incidence or types of adverse events within treatment groups in all the age subgroups analyzed. Conclusions: In this subgroup analysis of the HERO study, relugolix was effective regardless of age, and the benefit/risk profile remained favorable for relugolix compared with leuprolide, consistent with the overall population. Testosterone recovery was higher in the relugolix group than the leuprolide group for all age subgroups analyzed, with higher rates of recovery in younger versus older men. Clinical trial information: NCT03085095. [Table: see text]

5569 Background: The CARD trial (NCT02485691) compared cabazitaxel vs. an androgen receptor targeted agent (ART; abiraterone/enzalutamide) in mCRPC previously treated with docetaxel and the alternative ART (abiraterone/enzalutamide), in any order. These post hoc analyses assessed OS from various time points and the impact of prognostic factors. Methods: Patients with mCRPC previously treated with docetaxel and progressing ≤ 12 months on prior abiraterone/enzalutamide were randomized 1:1 to cabazitaxel (25 mg/m2 IV Q3W + daily prednisone + prophylactic G-CSF) vs. abiraterone (1000 mg PO + daily prednisone) or enzalutamide (160 mg PO). OS was calculated from date of diagnosis of metastatic disease, date of mCRPC, and start of 1st, 2nd or 3rd life-extending therapy (LET). A stratified multivariate Cox regression analysis assessed the impact of 14 prognostic factors on OS using a stepwise model selection approach with a significance level of 0.10 for entry into the model and 0.05 for removal. Results: In the CARD study (N = 255), median OS was longer with cabazitaxel vs. abiraterone/enzalutamide (13.6 vs 11.0 months; HR 0.64, 95% CI 0.46–0.89; p = 0.008). OS was numerically improved for cabazitaxel vs. abiraterone/enzalutamide when assessed from the time of diagnosis of metastatic disease or mCRPC, or from start of 1st or 2nd LET (Table). In the multivariate analysis, low hemoglobin, high baseline neutrophil to lymphocyte ratio, and high PSA values at baseline were associated with worse OS. In presence of these factors, the OS benefit observed with cabazitaxel versus abiraterone/enzalutamide remained significant (HR 0.63, 95% CI 0.42–0.94, p = 0.022). Conclusions: Cabazitaxel numerically improved OS vs. abiraterone/enzalutamide in patients with mCRPC previously treated with docetaxel and the alternative ART (abiraterone/enzalutamide), whatever the time point considered. The robustness of this OS benefit was confirmed by stratified multivariate analysis. Sanofi funded. Clinical trial information: NCT02485691 . [Table: see text]

5559 Background: In the CARD (NCT02485691) study, radiographic PFS (rPFS), PFS and OS were significantly improved with CBZ vs. androgen-signaling-targeted agents (ARTA; ABI or ENZ) in pts with mCRPC who had received docetaxel (DOC) and progressed within 12 months (mo) on an alternative ARTA. This analysis evaluated the impact of age (< 70 vs. ≥ 70 years) on the efficacy and safety of CBZ and ARTAs in CARD. Methods: 255 pts with mCRPC were randomized 1:1 to CBZ (25 mg/m2 IV Q3W + prednisone [P] + G-CSF) vs. ABI (1000 mg PO + P) or ENZ (160 mg PO) until disease progression, unacceptable toxicity or pt request. Pts were eligible if they had received ≥ 3 cycles of DOC and progressed ≤ 12 mo on the previous alternative ARTA. Primary endpoint was rPFS. Subgroup analysis of older (≥ 70 years; n = 135) and younger (< 70 years; n = 120) pts was pre-specified for rPFS; others were post hoc. Results: rPFS was significantly improved vs. ARTA in both older (median 8.2 vs. 4.5 mo; HR 0.58; 95% CI 0.38–0.89) and younger pts (median 7.4 vs. 3.2 mo; HR 0.47; 95% CI 0.30–0.74). Median OS for CBZ vs. ARTA was 13.9 vs. 9.4 mo (HR 0.66; 95% CI 0.41–1.06) in older pts and 13.6 vs. 11.8 mo (HR 0.66; 95% CI 0.41–1.08) in younger pts. PFS, tumor, PSA and pain responses also favored CBZ, regardless of age. Grade ≥ 3 adverse events (AEs) occurred in 57.8% vs. 49.3% of older pts receiving CBZ vs. ARTA and 48.4% vs. 42.1% in younger pts. AEs leading to death were more frequent with ARTA, mainly due to disease progression. Conclusions: CBZ had improved efficacy outcomes vs. ARTA in pts with mCRPC previously treated with DOC and the alternative ARTA, regardless of age. Grade ≥ 3 cardiac AEs were more frequent in older pts treated with ARTA. A higher rate of AEs was reported in older vs. younger pts, for ARTA and CBZ. CBZ and ARTA had different safety profiles in older compared with younger pts. Clinical trial information: NCT02485691 . Funding: Sanofi. [Table: see text]

5602 Background: LHRH agonists are the mainstay for medical castration in advanced prostate cancer; however, they cause an initial testosterone (T) surge with a delayed onset of castration and require depot injection. Relugolix is the first oral GnRH receptor antagonist, which was previously shown to rapidly suppress T levels. The HERO trial compared the safety and efficacy of relugolix with leuprolide acetate in advanced prostate cancer patients. Methods: HERO is a 48-week, global, pivotal phase III trial that randomized 934 patients with androgen-sensitive advanced prostate cancer in a 2:1 ratio to receive relugolix 120 mg orally QD after a single l or leuprolide acetate 3-month depot injection. The primary endpoint was to achieve and maintain serum T suppression to castrate levels (< 50 ng/dL) through 48 weeks. Key secondary endpoints included castration rates at Day 4, profound castration (< 20 ng/dL) rates at Days 4 and 15, PSA response rate at Day 15 and FSH levels at Week 25. Testosterone recovery was evaluated in a subset of 184 patients. Results: A total of 96.7% (95% CI: 94.9%, 97.9%) of men on relugolix achieved and maintained castration through 48 weeks compared to 88.8% on leuprolide. The difference of 7.9% (95% CI: 4.1%, 11.8%) demonstrated non-inferiority (margin -10%) and superiority (P < 0.0001) of relugolix to leuprolide. All key secondary efficacy endpoints tested demonstrated superiority over leuprolide (P < 0.0001) (Table). In the testosterone recovery subset, median T levels were 270.76 ng/dL in the relugolix compared to 12.26 ng/dL in the leuprolide group 90 days after discontinuation of therapy. In a prespecified analysis, the incidence of major adverse cardiovascular events (MACE) was lower in the relugolix group than in the leuprolide group (2.9% vs. 6.2%, respectively); otherwise the safety and tolerability profiles were generally similar. Conclusion: Relugolix achieved castration as early as Day 4 and demonstrated superiority over leuprolide in sustained T suppression through 48 weeks, faster T recovery after discontinuation and a 50% reduction in MACE. Relugolix has the potential to become a new standard for T suppression for patients with advanced prostate cancer. Clinical trial information: NCT03085095 . [Table: see text]

Contains fulltext : 195635.pdf (Publisher’s version ) (Open Access) Most men with advanced prostate cancer will develop bone metastases, which have a substantial impact on quality of life. Bone metastases can lead to skeletal-related events (SREs), which place a burden on patients and healthcare systems. For men with castration-resistant prostate cancer (CRPC) and bone metastases, the treatment landscape has evolved rapidly over the past few years. The relatively recent approvals of the hormonal agents abiraterone acetate and enzalutamide, second-line chemotherapy cabazitaxel, and the radiopharmaceutical radium-223 dichloride (radium-223), have provided clinicians with a greater choice of treatments. These compounds have benefits in terms of overall survival based on the results of pivotal phase 3 studies. The bisphosphonate zoledronic acid and the RANK ligand inhibitor denosumab are indicated for the prevention of SREs in men with metastatic CRPC but studies of these compounds have not demonstrated a survival benefit. The important question of the role of bisphosphonates or denosumab in combination with these new agents has thus materialised. Current and emerging evidence from clinical studies of abiraterone acetate, enzalutamide and radium-223, suggest that addition of bisphosphonates or denosumab to these new therapies may provide further clinical benefits for patients with prostate cancer and bone metastases. This evidence may help to shape clinical practice but are based largely on post hoc analyses of clinical trial data. It is therefore apparent that further data are required from both clinical studies and real-world settings to enable physicians to understand the efficacy and safety of combination therapy with the new agents plus bisphosphonates or denosumab.

Genitourinary cancers represent 12.8% of cancer in both sexes and 21.5% in men, accounting for 7% of cancer deaths in both sexes and 10.5% in men. The systemic treatment of prostate cancer and renal cell carcinoma does not rely on chemotherapy, with the exception of taxane docetaxel and cabazitaxel. Prostate cancer is primarily treated by androgen deprivation, by surgical castration or LHRH analogs, or by androgen receptor pathway inhibitor enzalutamide and abiraterone acetate. Renal cell carcinoma is nowadays treated with agents targeting survival and angiogenesis pathways, including tyrosine kinase inhibitors (TKIs) sorafenib, sunitinib, axitinib, and pazopanib; anti-vascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab; mammalian target of rapamycin (mTOR) inhibitors temsirolimus and everolimus; and oral inhibitor of tyrosine kinases MET, VEGFR, AXL, cabozantinib. Most recently, immune checkpoint inhibitors have made their way to genitourinary cancers, revolutionizing the treatment of urothelial cancers and renal cell carcinoma.

50 Background: In clinical practice, Ra-223 is often combined with Enza or Abi/pred. ERA 223 (NCT02043678) showed increased fracture risk with concurrent Ra-223+Abi/pred. We assessed real-world symptomatic skeletal events (SSEs) and overall survival (OS) of pts with mCRPC who received concurrent or layered Ra-223+Enza or Abi/pred. Methods: Patients with mCRPC treated with Ra-223 in US cancer clinics from 1/01/2013 to 6/30/2017 were identified from a Flatiron prostate cancer registry of electronic health records. Tx initiation defined subgroups: concurrent (both started within 30 days) or layered (1 started ≥30 days after the other). Baseline (BL) was the first dose of Ra-223. Descriptive analysis was performed for BL characteristics, SSEs, and OS (Kaplan–Meier). Results: Of 625 pts treated with Ra-223, 48% received Ra-223+Enza or Abi/pred. Layered Tx was more common (73%) than concurrent (27%). BL characteristics and clinical outcomes were summarized [Table]. Conclusions: Ra-223+Enza or Abi/pred Tx was mainly layered. SSE rates with layered vs concurrent Ra-223+Abi/pred varied between subgroups; results must be treated cautiously given small pt numbers and a non-randomized study. The ongoing PEACE III trial is investigating concurrent Ra-223+Enza; a Phase III study (ESCALATE) exploring layered Ra-223+Enza is planned. Clinical trial information: NCT02043678. [Table: see text]

703 Background: SURTIME compared immediate CN followed by sunitinib 50mg/day (4/2 weeks on-off) 4 weeks after surgery (n=50) versus 3 cycles sunitinib followed by CN in the absence of progression and continued sunitinib 4 weeks after surgery (n=49). In the intention to treat analysis, the hazard ratio of the secondary endpoint overall survival (OS) favored deferred CN [0.57 (CI: 0.34–0.95, p=0.032)] with a median OS of 32.4 (CI: 14.5-65.3) versus only 15.0 months (CI: 9.3–29.5), following immediate CN. We investigated differences in exposure to systemic therapy between the two arms. Methods: Post-hoc exploratory analysis of number of patients receiving sunitinib, overall response rate (ORR) by RECIST 1.1, length of drug exposure and dose intensity in the immediate and deferred arm. Descriptive methods and 95% confidence intervals (CI) were used. Results: In the deferred arm, 97.7% (CI: 89.3-99.6; n=48) received sunitinib versus only 80% (CI: 66.9-88.7, n=40) in the immediate arm. Following immediate CN, 19.6% had confirmed progression at an interval CT scan 4 weeks after CN compared to baseline and 25% started with sunitinib > 4 weeks after surgery. At week 16, 46.0% had progressed at metastatic sites in the immediate CN arm versus 32.7% in the deferred arm, who had a per-protocol recommendation against nephrectomy. In the deferred arm, 83% completed 3 cycles sunitinib with 77.1% at >90%-120% relative dose intensity and an ORR of 29%, reducing the median sum of target lesions from 162 to 127 mm prior to planned CN.Of the patients who started with sunitinib in the immediate (n=40) or continued in the deferred arm after CN (n=29) median duration of treatment was 140 versus 351 days. Conclusions: With immediate CN fewer patients receive systemic therapy, which is administered later and shorter compared to the deferred approach. Starting systemic therapy with sunitinib leads to early and more profound control of the disease and identification of progression prior to planned CN which may translate into the observed survival benefit. Clinical trial information: NCT01099423.

5066 Background: Somatic DRD deficiency in 15-30% of mCRPC pts have been observed and inhibition of enzyme poly ADP ribose polymerase (PARP) could prove beneficial. We aimed to define DRD status using plasma from pts treated on AA and evaluate associations with prospectively-collected outcome measures. Methods: Plasma DNA samples (128 baseline [BL], 134 cycle 2 day 1 [C2D1], 46 progression [PROG]) from chemotherapy-naïve mCRPC pts in a phase 2 study (NCT01867710) evaluating AA+P/D were subjected to custom target-capture next-generation sequencing. DRD assay was optimized and validated to detect pathogenic point mutations, small insertions/deletions, and copy number alternations (DRD+) in 8 DRD genes: BRCA1, BRCA2, FANCA, ATM, CHEK2, HDAC2, BRIP1, and PALB2. Analysis for genomic aberrations was a secondary exploratory objective. Associations with overall survival (OS), progression-free survival (PFS), and radiographic PFS (rPFS) were assessed using Cox regression models and Kaplan Meier analyses. Results: 11.7% of BL and 17.4% of PROG were DRD+. Bi-allelic was observed in 73.3% of BL DRD+ samples. Shorter PFS was observed in BL DRD+ vs DRD- (5.3 vs 15.5 mo; HR: 2.32; 95%CI:1.39-4.28; P < 0.002). Median PFS for BL DRD biallelic + vs DRD biallelic- was 5.1 vs 15.4 mo (HR: 2.49; 95% CI: 1.23-4.38; P < 0.0095). For multivariate analysis using DRD+, ALP, and LDH as covariates, DRD+ (HR: 2.1; 95% CI: 1.18-3.75; P < 0.012) and high ALP (HR: 1.66; 95% CI: 1.08-2.56; P < 0.021) were strongly associated with worse PFS. Median OS for BL DRD+ vs DRD- was 28.8 vs 41.3 mo (HR: 1.67; 95%CI:0.88-3.18; P = 0.116). Median rPFS for BL DRD+ vs DRD- was 16.2 vs 20.9 mo (HR: 1.64; 95%CI:0.83-3.21; P = 0.152). Of 39 Pts with BL, C2D1 and PROG samples, 3 were DRD+ (7.7%) at all 3 timepoints, 3 (7.7%) only at BL, 3 (7.7%) only at PROG (bi-allelic), 2 (5.1%) had extra deletion at PROG. Conclusions: Patients with mCRPC harboring DRD+ have worse outcomes with AA and represent a population with an unmet medical need.

5026 Background: In clinical practice, Ra-223 is often combined with Enza or Abi/pred. ERA 223 (NCT02043678) showed increased fracture risk with concurrent Ra-223+Abi/pred. We assessed real-world symptomatic skeletal events (SSEs) and overall survival (OS) of pts with mCRPC who received concurrent or layered Ra-223+Enza or Abi/pred. Methods: Patients with mCRPC treated with Ra-223 in US cancer clinics from 1/01/2013 to 6/30/2017 were identified from a Flatiron prostate cancer registry of electronic health records. Treatment initiation defined subgroups: concurrent (both started within 30 days) or layered (1 started ≥30 days after the other). Baseline (BL) was the first dose of Ra-223. Descriptive analysis was performed for BL characteristics, SSEs, and OS (Kaplan–Meier). Results: Of 625 pts treated with Ra-223, 48% received Ra-223+Enza or Abi/pred. Layered treatment was more common (73%) than concurrent (27%). BL characteristics and clinical outcomes were summarized [Table]. Conclusions: In a real-world setting, Ra-223+Enza or Abi/pred treatment was mainly layered. SSE rates with layered vs concurrent Ra-223+Abi/pred varied between subgroups; results must be treated cautiously given small pt numbers and a non-randomized study. The ongoing PEACE III trial is investigating concurrent Ra-223+Enza; a Phase III study (ESCALATE) exploring layered Ra-223+Enza is planned. [Table: see text]

5044 Background: The Phase 3 ARCHES trial (NCT02677896) evaluated the efficacy and safety of ENZ + androgen deprivation therapy (ADT) vs placebo (PBO) + ADT in 1150 men with mHSPC. Here we report patient-reported outcome (PRO) data using Functional Assessment of Cancer Therapy-Prostate (FACT-P) and Brief Pain Inventory Short Form (BPI-SF). Methods: FACT-P and BPI-SF were assessed at baseline (BL), week (wk) 13, and then every 12 wks until disease progression. Longitudinal changes were assessed using mean scores and mixed-model repeated measures; lower BPI-SF scores represent less pain/interference; higher FACT-P scores represent better HRQoL. Time from BL to first deterioration in PRO score was assessed by Kaplan-Meier estimates and Cox proportional hazards models. Clinically meaningful difference was defined by change from baseline ≥10 for FACT-P total and ≥2 for worst pain/severity. Results: PRO instrument completion rates were high (88−96%) up to wk 73. At BL, men in both arms were generally asymptomatic and reported good HRQoL (FACT-P total: ENZ + ADT, 113.9; PBO + ADT, 112.7) and low pain (worst pain [item 3]: ENZ + ADT, 1.80; PBO + ADT, 1.77). HRQoL and pain scores remained stable over time and there were no clinically meaningful differences between groups in change from BL to wk 73. The proportion of men with no change or improvement in PRO scores (67–88%) was similar in both groups at all time points up to wk 73. There was no significant difference between arms for time to deterioration in FACT-P total (HR 0.90 [95% CI] (0.74, 1.09); p = 0.2998). ENZ + ADT significantly delayed time to pain progression for worst pain (HR 0.82 [0.69, 0.98]; p = 0.0322) and pain severity (HR 0.79 [0.65, 0.97]; p = 0.0209) vs PBO + ADT. Conclusions: Men with mHSPC were generally asymptomatic and had high levels of HRQoL and low levels of pain at BL, likely due to most men initiating ADT several months prior to study entry. No clinically meaningful differences in HRQoL were observed between ENZ and PBO. The prolongation in radiographic progression-free survival observed with ENZ + ADT was accompanied by a significantly prolonged time to progression of worst pain and pain severity vs PBO + ADT. Clinical trial information: NCT02677896.

5007 Background: Skeletal fractures, pathological or not, are a frequent and underestimated side-effect of systemic treatment of metastatic castration resistant prostate cancer (mCRPC). The ERA223 trial (NCT02043678) was recently unblinded following the report of a significant increase in the fracture rates when abiraterone is combined with Ra223. Hence, FDA and EMA advised against this combination. The question whether mandated use of bone protecting agents (BPA), zoledronic acid or denosumab, would have mitigated the fracture risk and whether this risk also exists in the enzalutamide/Ra223 combination is presently unknown. Methods: The phase III EORTC-1333-GUCG/PEACEIII (NCT02194842) trial compares enzalutamide vs. a combination of Ra223 and enzalutamide in asymptomatic or mildly symptomatic mCRPC patients (https://www.eortc.org/research_field/clinical-detail/1333/). After the unblinding of ERA223, the trial was amended (v4.0, April 19, 2018) to mandate that all patients must start a BPA. We report the fracture rate in the safety population of 146 treated patients as of 28/01/2019. Results: Overall, 54.2% of the patients in the enza/Ra223 arm and 51.4% of the enza arm did not receive BPA; 18.0% in the enza/Ra223 arm and 27.0% in the enza arm did not use BPA at randomization, but started during protocol treatment according to the v4.0 amendment. 27.8% and 21.6% respectively, received BPA as of randomization. In total, 45.8% of enza/Ra223 patients and 48.6% of enza only patients receive bone protection on treatment. The fracture rate is reported in the table. Conclusions: There is a 13% risk of fracture with enzalutamide in asymptomatic mCRPC, in line with previous reports. This risk is significantly increased to 33% when Ra223 is added to enzalutamide. Strikingly, the risk is almost abolished by mandatory continuous administration of BPA starting at least 6 weeks before the first injection of Ra223, thus emphasizing the importance of treating mCRPC patients with BPA. Clinical trial information: NCT02194842. [Table: see text]

183 Background: Current PCWG3 guidelines for men with mCRPC define BS progression during therapy as requiring confirmation of new bone lesions that develop over time with additional new lesions. New unconfirmed BS lesions may reflect slow progression or a favorable osteoblastic reaction called a “BS flare” that can be misinterpreted as radiographic progression and lead to premature therapy discontinuation. The prevalence and clinical impact of BS flare is unknown for ENZA. Methods: We analyzed the association of BS flare with clinical outcomes and quality of life (QoL) in a retrospective analysis of two phase 3 trials of men with mCRPC treated with ENZA after (AFFIRM n = 1199) and before (PREVAIL n = 1717) docetaxel. Early and late BS flare was defined as new lesions on the first posttreatment BS (weeks 9-13) or subsequent BS, respectively, that were not confirmed to meet progression criteria on the next BS, while also requiring responding/stable PSA and soft-tissue disease. Results: Unconfirmed BS lesions were observed in 22% and 25% of stable/responding men receiving ENZA in AFFIRM and PREVAIL, respectively. Most BS flares were early, but late flares (week 17 or later) were seen in 2% and 13% of men, respectively. Unconfirmed BS lesions (early or late) had no impact on OS (HR 0.87; 95% CI 0.62-1.21) or rPFS (HR 0.91; 95% CI 0.58-1.44) in PREVAIL, but were associated with worse OS (HR 2.26; 95% CI 1.55-3.30) and rPFS (HR 1.73; 95% CI 1.33-2.26) in AFFIRM. Soft-tissue responses and PSA declines were more prominent in chemo-naïve men with unconfirmed BS lesions, which also had no impact on QoL or pain deterioration in either setting. Conclusions: BS flare occurred in ≈25% of responding men with mCRPC receiving ENZA and was not associated with adverse outcomes in chemo-naïve men. Our findings support the importance of avoiding premature treatment discontinuation in the presence of unconfirmed new BS lesions in the first 4 months of therapy. Worse outcomes associated with unconfirmed lesions in men post docetaxel illustrate the need for improved functional bone imaging in mCRPC and broader patient assessment to decide on treatment continuation. Clinical trial information: NCT00974311; NCT01212991.

237 Background: Androgen receptor inhibitor enzalutamide improves survival in patients with metastatic CRPC (mCRPC) and reduces risk of metastasis or death versus placebo in patients with non-metastatic CRPC (nmCRPC). This post hoc analysis evaluated the incidence of adverse events (AEs) of special interest reported with enzalutamide versus placebo in CRPC trials. Methods: Safety data from four Phase 3, placebo-controlled enzalutamide trials in men with CRPC (PROSPER, nmCRPC, NCT02003924; PREVAIL, mCRPC, NCT01212991; AFFIRM, mCRPC, NCT00974311; and 9785-CL-0232, mCRPC, NCT02294461) were assessed for AEs of special interest, including ischemic heart disease (IHD) [defined by narrow Standardised MedDRA Queries “Myocardial Infarction”/“Other Ischemic Heart Disease”], falls, and fractures. Data were reported as overall incidence and adjusted for treatment exposure (per 100 patient-years), and summarized as follows: patients receiving enzalutamide (n = 2799) and placebo (n = 1898) in all four Phase 3 trials. Results: Median treatment duration was 13.73 months with enzalutamide and 4.80 months with placebo in the combined Phase 3 trials. Overall incidence of IHD was higher with enzalutamide versus placebo in the combined Phase 3 trials (Table), remaining higher once adjusted for treatment exposure (2.5 with enzalutamide vs. 2.2 with placebo). Similarly, exposure-adjusted rate of falls and fractures were also higher with enzalutamide versus placebo (Table). Clinical trial information: NCT02003924 (PROSPER); NCT01212991 (PREVAIL); NCT00974311 (AFFIRM); NCT02294461 (9785-CL-0232). Conclusions: In this combined analysis of CRPC trials, incidences of IHD, falls, and fractures were higher with enzalutamide versus placebo in all patients. Efforts to identify patients at high risk for these AEs and reduce their risk, e.g. via exercise and cardiovascular risk reduction, are important in these patients, particularly in elderly men and those with cardiovascular comorbidities.[Table: see text]

233 Background: PROSPER data were analyzed to assess the relationship between time to worsening of urinary, bowel, and hormonal treatment-related symptoms and prostate-specific antigen (PSA) response, and the longitudinal association between symptom changes and metastasis-free survival (MFS). Methods: 1401 patients (pts) with nmCRPC at high metastasis risk were randomized 2:1 to enzalutamide (ENZA) or placebo. Urinary, bowel, and hormonal treatment-related symptoms were assessed with the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-PR25) at baseline (BL) and every 16 weeks. The association between time to first clinically meaningful symptom worsening and PSA response (≥50% decline from BL) was analyzed with stratified Cox regression using treatment as a covariate. Longitudinal symptom changes and MFS were evaluated in joint models using symptom scores as covariates, adjusted for treatment and clinical/demographic variables. The proportion of pts with improvement, no change, or deterioration at metastasis were analyzed by treatment group. Results: 723/1401 (52%) pts were PSA responders, including >90% of ENZA pts. PSA responders were significantly less likely to develop urinary, bowel, and hormone treatment-related symptoms vs. non-responders (hazard ratio [HR] 0.58 [95% confidence interval 0.41, 0.81]; 0.59 [0.43, 0.80]; and 0.70 [0.51, 0.97], respectively). Every 9-point increase in urinary symptom score was associated with a 10% increased metastasis risk (HR 1.1 [1.05, 1.15]). Bowel and hormonal symptoms did not predict metastasis. Most pts reported no EORTC score changes at metastasis and maintained stable urinary/bowel symptoms, with no major observed symptom differences between treatment groups. Conclusions: ENZA delays metastasis and extends time to symptom worsening. A ≥50% PSA reduction from BL is associated with a reduction in risk for urinary, bowel, and hormonal treatment-related symptom worsening; changes in urinary symptoms from BL also predict metastases. Clinical trial information: NCT02003924 (PROSPER).

253 Background: Limited data exist on Ra-223 use in combination with Abi in a real-world setting. This retrospective study evaluated clinical outcomes in pts with mCRPC who received concurrent or layered Ra-223 + Abi treatment. Methods: This study used the Flatiron prostate cancer registry of electronic health records of pts with mCRPC treated with Ra-223 in US cancer clinics between 1/01/2013 and 6/30/2017. Two sub-cohorts were defined: pts treated with Ra-223 + Abi in a concurrent (both started within 30 days) or layered fashion (one of the two started over 30 days later). Descriptive analysis was done for baseline (BL) characteristics (prior to start of Ra-223), prior therapies, and clinical outcomes including skeletal-related events (SREs) and overall survival (OS). Results: 625 pts were treated with Ra-223; 136 (21.8%) received Ra-223 + Abi. Most received layered therapy (n = 97, 71%); concurrent start was less common (n = 39, 29%) [Table]. Conclusions: Prior to the start of Ra-223 therapy, half of the pts had prior SREs; almost one-fifth had prior pathologic fractures. Pts treated with Ra-223 + Abi had also received prior chemo and/or enzalutamide. SRE occurrence seems higher for concurrent treatment, but results should be cautiously interpreted due to low concurrent cohort size. OS in both cohorts exceeded the OS in the Phase III ALSYMPCA study (14.9 mo).[Table: see text]

256 Background: In the era of expanding therapeutic options for mCRPC, there is a growing need to develop an optimal treatment sequence. This real-world study evaluated treatment patterns and outcomes in mCRPC patients. Methods: This retrospective cohort study used the Flatiron prostate cancer core registry (Jan 2013 to Sep 2017) to assess real-world treatment patterns (lines of therapy and transitions to subsequent lines) and outcomes (overall survival, OS) in patients with mCRPC. Descriptive analysis was performed for treatment patterns, and the Kaplan–Meier method was used to analyze OS. Results: This study comprised 2559 patients with mCRPC who received up to three lines of therapy. 23% of patients did not receive a life-prolonging therapy after the initial diagnosis of mCRPC. In the first-line (1L) setting, abiraterone (Abi, 37%) was the most-prescribed therapy, followed by enzalutamide (Enza, 28%) and docetaxel (15%). In the second line (2L), combination therapies were frequent (17%), with rates similar to taxane-based chemotherapy (docetaxel or cabazitaxel). Enza was the most-common 2L therapy used after Abi, and vice versa. Radium-223 (Ra-223) was prescribed as 1L therapy in 5% and 2L therapy in 9% of patients, either as monotherapy or part of a combination regimen. When Ra-223 was used in the 1L setting, similar proportions of patients received subsequent therapy with Enza (14%), Abi (13%), or chemotherapy (11%). Ra-223 was commonly used in the third line (14%), but less frequently than chemotherapy (36%). After each line, ~50% of patients did not receive a subsequent life-prolonging agent. Overall, 66% of patients used bone health agents at any time (denosumab, 48%; zoledronic acid, 24%). The median OS from the diagnosis of mCRPC was 21 months. Conclusions: This real-world study shows that not all patients with mCRPC received a life-prolonging therapy. Among patients who received an anti-cancer therapy, approximately half did not receive a subsequent life-prolonging therapy. Abi and Enza were the most-common 1L therapies, and their back-to-back use was common despite reported cross-resistance and limited benefit.

5067Background: pAR gene aberrations in mCRPC patients (pts) may be associated with worse outcome on AA+P/D. Methods: This was an international, multi-institutional, open-label phase 2 study of AA ...

5043Background: We used the PROSPER trial (NCT02003924) to assess (a) the relationship between time to HRQoL deterioration and prostate-specific antigen (PSA) response and (b) the association betwe...

5010Background: The Phase 3 PROSPER trial (NCT02003924) showed a statistically significant improvement in metastasis-free survival (MFS) with enzalutamide (ENZA; n = 933) vs. placebo (PBO; n = 468)...

TPS156 Background: Adjuvant ADT with an LHRH analog (LHRHA) given before, during and after radiotherapy (RT) is standard of care for high risk localised prostate cancer (PC). Enzalutamide improves overall survival (OS) in castration-resistant, metastatic prostate cancer. We hypothesized that the addition of enzalutamide to adjuvant ADT and RT will improve outcomes. The aim is to determine the effects of enzalutamide versus a conventional non-steroidal anti-androgen (NSAA) as part of neoadjuvant and adjuvant ADT in men undergoing RT for high risk, localized PC. Methods: DESIGN: Open label, randomised, phase 3 trial including ANZ, USA, UK, Ireland and Europe. ENDPOINTS: OS (primary), cause-specific survival, PSA progression free survival (PFS), clinical PFS, time to subsequent hormonal therapy, time to castration-resistant disease (PCWG2 criteria), metastasis free survival (MFS), adverse events and health-related quality of life (HRQOL). CORRELATIVE OBJECTIVES: identification of prognostic/predictive biomarkers from archival tumour tissue and serial blood samples. SAMPLE SIZE: 800 participants with a minimum follow-up of 5.5 yrs is designed to give 80% power to detect 33% reduction in the hazard of death assuming 5-year survival rate of 76% amongst controls. TREATMENT: Enzalutamide 160mg daily for 24 months versus conventional NSAA for 6 months. All participants receive LHRHA for 24 months, and RT starting about week 16 delivered as 78Gy in 39#, or 46Gy in 23# plus brachytherapy (nodal RT optional for N0, mandatory for N1). ASSESSMENTS: Baseline, then every 8 weeks until year 2, then 3-4 monthly until year 5, 6-monthly until year 7, then annually. Imaging with CT/MRI and bone scan at baseline, PSA progression, then 6 monthly until re-initiation of ADT, when PCWG2 criteria for CRPC are met and then 3 monthly until evidence of metastases. 623 participants recruited from 61 sites as of 16 October 2017. ENZARAD is an investigator-initiated cooperative group trial led by ANZUP Cancer Trials Group with funds and product from Astellas. Clinical trial information: NCT02446444.

TPS383 Background: The addition of either docetaxel or abiraterone acetate plus prednisone to androgen deprivation therapy (ADT) improves overall survival (OS) compared with ADT alone in men with mHSPC. It is hypothesized that other androgen receptor (AR)-targeted therapies could be combined with docetaxel for mHSPC. Darolutamide (ODM-201) is an investigational oral AR antagonist with a unique chemical structure and negligible blood-brain barrier penetration that inhibits tumor growth by binding to AR and AR mutants (eg, W742L and F877L) with high affinity and specificity. In phase 1/2 ARADES and phase 1 ARAFOR trials, darolutamide demonstrated antitumor activity and was well tolerated in men with metastatic castration-resistant prostate cancer (mCRPC). ARASENS will evaluate the addition of darolutamide to standard ADT and docetaxel in men with mHSPC. Methods: This international, randomized, double-blind, placebo-controlled phase 3 trial (NCT02799602) is being conducted at > 300 sites in 23 countries. ~1300 men with newly diagnosed mHSPC will be randomized 1:1 to darolutamide (600 mg orally twice daily) or matching placebo. All patients will receive standard ADT + docetaxel (6 cycles). Patients will be stratified by disease extent and alkaline phosphatase level. Key inclusion criteria: histologically or cytologically confirmed PC with documented metastases, started ADT ± first-generation antiandrogen therapy ≤12 weeks before randomization, and ECOG performance status 0-1. The primary end point is OS. Secondary end points include time to mCRPC, initiation of subsequent anticancer therapy, symptomatic skeletal event (SSE)-free survival, time to first SSE, first opioid use, pain progression, and worsening of physical symptoms. Safety will be assessed. ARASENS is actively enrolling at > 280 sites across 23 countries. Clinical trial information: NCT02799602.

TPS406 Background: Androgen deprivation therapy (ADT) by LHRH analogues aims to lower serum testosterone. ADT is associated with several side effects that include hot flushes, depression, loss of libido, metabolic disturbances leading to an increase risk of cardiovascular disease, increased bone resorption leading to increased risk of osteoporosis and skeletal fracture. AR antagonists may circumvent these side effects by suppressing AR transcription by competitive inhibition of AR, without lowering systemic testosterone. In Europe, first generation AR antagonists bicalutamide 150 mg is registered for the treatment of non-metastatic hormone-naïve PCa. is a novel AR antagonist that is structurally distinct with higher AR-binding affinity compared to bicalutamide, enzalutamide, and apalutamide. The aim of this trial is to investigate the activity, safety and tolerability of darolutamide as single agent, as an alternative to LHRH analogues in men requiring ADT. Methods: EORTC-1532-GUCG (NCT02972060) will randomize 250 men with hormone-naïve PCa 1:1 to 600 mg (2× 300-mg tablets) bid of darolutamide1 or LHRH agonist or antagonist, stratified for type of ADT (agonist vs. antagonist), disease extent (measurable, non-measurable, vs. no metastasis) and age (≥70 vs < 70 years). Key inclusion criteria include histologically confirmed asymptomatic PCa (all stages) for whom continuous ADT is indicated for a minimum period of 24 weeks. Patients with up to 4 confirmed not visceral metastases, are allowed. Baseline total testosterone should be ≥ 8 nmol/L or 230 ng/dL. Primary endpoint is PSA response assessed at 24 weeks, defined as a ≥ 80% decline in PSA at week 24 in the darolutamide study arm. The ADT arm is used as an internal non comparative control. Key secondary endpoints include: Change in hormone-treatment related symptoms scale of the EORTC QLQ-PR25 at 24 weeks (comparison between arms); objective response rate at 24 weeks in patients with measurable disease at baseline, safety according to NCI-CTC version 4.0. Clinical trial information: NCT02972060.

352 Background: Among bone-targeted radio-isotopes (RI), Radium-223 (an α-emitter) is the only one with clearly demonstrated overall survival (OS) benefit in men with castration-resistant prostate cancer (CRPC). The aim of this meta-analysis is to estimate the OS impact of RI in men with CRPC. Methods: An individual patient data meta-analysis was carried out from randomized trials with inclusion period 1993-2013. Eligible trials included more than 50 patients, mandated bone metastases from CRPC and randomly evaluated RI. Endpoints were OS (primary), symptomatic skeletal events (SSE) and toxicity. A fixed-effect model was used. The log-rank test stratified by trial was used to estimate individual and overall hazard ratios (HR). Subset analyses were performed by the type of radiation (α vs. β emission) and by trial comparison: RI + Chemotherapy (CT) vs. CT, RI+ External beam radiotherapy (EBRT) vs. EBRT, RI vs. EBRT. Results: From 9 identified trials, data from 6 trials comprising 2081 patients (min: 64, max: 921) were collected with 2 trials representing 80% of data. The data from 3 trials (n = 341) were not available. The overall effect on OS favoured RI with HR = 0.86 [0.77-0.95] but high heterogeneity between trials (p < 0.001, I2= 79.6%). The overall effect of α- emitters on OS (HR = 0.70 [0.58; 0.83], 2 trials, n = 985) significantly differed from that of β-emitters (HR = 0.96 [0.84; 1.10], n = 4 trials, n = 1096) (interaction p = 0.0041). The overall effect on SSE favoured RI with HR = 0.81 [0.69-0.93] (4 trials, n = 1806) with marked between trial heterogeneity (p = 0.08, I² = 55.3%) and a significant difference (p = 0.02) by the type of RI (α-emitters: HR = 0.65 [0.52-0.82]-2 trials, β-emitters: HR = 0.93 [0.77-1.13]-2 trials). Conclusions: In men with metastatic CRPC a significant improvement of OS and SSE was obtained with bone targeted α-emitter radio isotopes, but not with β-emitter. However, some between trial heterogeneity of effects on OS need further investigations.

TPS390 Background: α-emitting radiopharmaceutical Ra-223 reduces the risk of death by 30% vs placebo in phase 3 ALSYMPCA (Parker et al. NEJM 2013). Ra-223’s favourable safety profile and lack of significant toxicity support combining it with other agents. The ALSYMPCA trial was developed to add Ra-223 on the contemporary standard of care that did not include last generation AR pathway inhibitors enzalutamide, one of the modern reference treatments for asymptomatic or moderately symptomatic metastatic CRPC (Gillessen et al. Eur Urol. 2017). In addition Ra-223 is registered in symptomatic prostate cancer (PCa), a very late stage of modern patient disease. There is thus a good rationale to combine Ra-223 to modern AR pathway inhibitors and to initiate the treatment in asymptomatic or moderately symptomatic patients. Methods: The EORTC 1333-GUCG study will run in 51 sites (21 activated) across 7 European countries, 4 sites in US and 12 sites in Canada. The study is an intergroup initiative between EORTC (Coordinating Group), UNICANCER; Cancer Trials Ireland (Ireland), ACCRU (The United States), and CUOG (Canada). A total of 560 patients will be randomized in a 1:1 ratio to receive enzalutamide 160 mg q.d. p.o. or enzalutamide at the same dose and Ra223 at 55 kBq/kg i.v. monthly for 6 months. Patients will be stratified by country, pain (BPI 0-1 vs BPI 2-3), prior docetaxel use (no vs yes) and use of bone targeting agents (no vs yes). The main inclusion criteria require asymptomatic or mildly symptomatic (defined as no opioids and BPI-SF question 3 < 4), metastatic to bone with ≥ 2 bone metastases with or without additional lymph node metastases. Visceral metastases are not allowed. The primary endpoint is radiological progression-free survival (rPFS1), according to PCWG3. Secondary endpoints include: overall survival, PCa specific survival, 1st symptomatic skeletal event (SSE), time to initiation of next systemic anti-neoplastic therapy, time to pain progression, health-related quality of life (EQ-5D-5L and BPI). Clinical trial information: NCT02194842.

199 Background: Androgen receptor inhibitor enzalutamide (ENZA) improves survival in patients with metastatic CRPC. As the liver is the main route of ENZA elimination, this post hoc analysis evaluated the hepatic effects of ENZA versus comparators in controlled CRPC trials. Methods: Safety data from two large Phase 3, placebo (PBO)- (PREVAIL, NCT0121299; AFFIRM, NCT00974311) and two smaller Phase 2, bicalutamide (BIC)-controlled (STRIVE, NCT01664923; TERRAIN, NCT01288911) ENZA trials in men with CRPC were assessed for hepatic impairment-related adverse events (AEs) using the following standardized narrow MedDRA queries V19.1: hepatic failure, fibrosis and cirrhosis, and other liver damage-related conditions; hepatitis, non-infectious; and liver-related investigation, signs, and symptoms. Liver-related laboratory test results were also evaluated. Data were summarized as follows: patients receiving ENZA in Phase 3 trials (n = 1671); patients receiving ENZA in Phase 2 trials (n = 380); patients receiving PBO (n = 1243); patients receiving BIC (n = 387); and combined ENZA-treated patients (n = 2051). Results: Percentages of hepatic impairment-related AEs ranged between 2.9% and 4.5% with ENZA, and were 2.7% with PBO and 5.4% with BIC (Table). The most common hepatic impairment-related AEs were increased aspartate (AST) and alanine aminotransferase (ALT; Table). Within each trial, the incidences of grade ≥3 AEs were similar, and dose reductions or discontinuations due to hepatic impairment-related AEs were low (Table). When adjusted for treatment exposure, AEs per 100 patient-years were lower with ENZA versus either PBO or BIC (Table). Conclusions: This combined analysis of CRPC trials demonstrates no hepatic safety signal with ENZA and thus routine liver tests are not required. Clinical trial information: NCT0121299; NCT00974311; NCT01664923; NCT01288911. [Table: see text]

e16034 Background: The prognostic relevance of the primary location of urothelial cell carcinoma (UCC) on outcomes is poorly documented. This parameter has been studied in 3 EORTC trials in advanced UCC that included patients with different initial primary tumor locations. Methods: We used the data prospectively collected in three EORTC advanced UCC studies 30924 (M-VAC versus High dose M-VAC), 30986 (MCAVI versus GC, among patients unfit for CDDP), 30987 (GC-Paclitaxel versus GC, among patients fit for CDDP). Ineligible patients and other tumor locations were excluded. Patients all had measureable distant metastases or unresectable UCC and WHO performance status 0-2. Patients were grouped by primary tumor location as bladder (BCa) versus upper urinary tract (UTUC). PFS and OS by tumor location was tested in Cox proportional hazard regression stratified by study and treatment using at 2-sided α of 0.05. Results: Of the 1,039 patients, 85.3% and 14.7% patients had BCa and UTUC, respectively. Patient and disease characteristics (Table) suggested better performance status and slightly more males among patients with GCa. With a median follow up of 4.8 years (IQR:4.0-6.7), 733 deaths were recorded and 925 had progressed or died. OS and PFS did not differ significantly by tumor location overall (P=0.317 and P=0.685 respectively, Table 1), but there is significant heterogeneity across treatments (heterogeneity P=0.0450 for OS and P=0.0121 for PFS) with a suggestion of differential results in the M-CAVI arm for unfit patients. Conclusions: Primary UTUC location is uncommon in advanced UCC and did not seem to markedly impact PFS or OS. However, the findings may vary according to treatment. [Table: see text]

TPS5092 Background: Androgen deprivation therapy (ADT) ± docetaxel is recommended first-line therapy for mHSPC, but most patients progress to castration-resistant PC (CRPC). BAY-1841788 (ODM-201) is an investigational oral androgen receptor (AR) antagonist that has a unique chemical structure designed to block the growth of cancer cells through binding to the AR with high affinity and inhibiting the receptor function. In preclinical studies, ODM-201 and its main circulating metabolite are active also in known AR mutants (eg, W742L, F877L), and have been found to have negligible blood-brain barrier penetration. In the phase 1 ARAFOR and phase 1/2 ARADES trials, ODM-201 had antitumor activity and was well tolerated in men with mCRPC (Massard et al. Eur Urol. 2016;69:834‒840; Fizazi et al. Lancet Oncol. 2014;15:975‒985). Given this promising activity in mCRPC, the ARASENS trial is evaluating ODM-201 plus standard ADT + docetaxel in men with metastatic disease (mHSPC). Methods: This international, randomized, double-blind, placebo-controlled, phase 3 trial (NCT02799602) is being conducted in 23 countries. ~1300 men with newly diagnosed mHSPC will be randomized 1:1 to either ODM-201 600 mg twice daily (2×300 mg tablets) orally with food or placebo, both with ADT + docetaxel (6 cycles after randomization), and stratified by extent of disease and alkaline phosphatase levels. Key inclusion criteria are histologically or cytologically confirmed PC with documented metastases, started ADT ± first-generation anti-androgen therapy ≤12 weeks before randomization, and Eastern Cooperative Oncology Group performance status 0 or 1. The primary objective is to show superior overall survival with ODM-201 vs placebo, both with ADT + docetaxel. Secondary end points include time to CRPC, initiation of subsequent anticancer therapy, symptomatic skeletal event-free survival (SSE-FS), time to first SSE, initiation of opioid use, pain progression, and worsening of physical symptoms, all measured at 12-week intervals. Safety will be assessed by adverse events. The trial is open for enrollment; first patient first visit was in November 2016 and > 10 sites are open for recruitment and enrolling patients. Clinical trial information: NCT02799602.

5042 Background: Ra-223, a targeted alpha therapy, prolonged survival with good safety in metastatic castration-resistant prostate cancer (mCRPC) in the phase 3 ALSYMPCA trial. REASSURE will evaluate Ra-223 short- and long-term safety in routine clinical practice settings. This is the first planned interim analysis (median 7 mo observation). Methods: This global, prospective, single-arm, observational study enrolled pts with mCRPC with bone metastases (mets) for whom Ra-223 therapy was planned. Follow-up will continue up to 7 years after last Ra-223 dose. Results: 1106 pts (437 N. America, 665 Europe, 4 not recorded) enrolled from 2 Sep 2014 to 22 Sep 2016. Baseline data are available from 583 pts receiving 1st- (1L), 2nd- (2L), or ≥3rd-line (≥3L) Ra-223 for mCRPC(Table). The majority of pts (n=369, 63%) completed 5–6 doses (1L, 70%; 2L, 64%; ≥3L, 49%); median 6 doses (1L,6; 2L, 6; ≥3L, 4). Treatment-emergent drug-related AEs occurred in 215 pts (37%). Post-treatment grade 3/4 thrombocytopenia occurred in 14 pts (2.4%) and anemia in 45 (7.7%). Conclusions: In routine clinical practice, Ra-223 was associated with no short-term safety concerns and appeared to be used in pts with less advanced mCRPC than in ALSYMPCA. The majority of pts on 1L/2L Ra-223 therapy received 5–6 doses. Ra-223 was often used with abiraterone or enzalutamide, but not chemotherapy. The next interim analysis in 2019 will report long-term safety and outcomes on all pts. Clinical trial information: NCT02141438. [Table: see text]

5022 Background: Prognostic models require updating to reflect contemporary medical practice. In a post hoc analysis of the phase 3 PREVAIL trial (enzalutamide vs placebo), we identified prognostic factors for overall survival (OS) in chemotherapy-naive men with mCRPC. Methods: Patients were randomly divided 2:1 into training (n = 1159) and testing (n = 550) sets. Using the training set, 23 predefined candidate prognostic factors (including treatment) were analyzed in a multivariable Cox model with stepwise procedures and in a penalized Cox proportional hazards model using the adaptive least absolute shrinkage and selection operator (LASSO) penalty (data cutoff June 1, 2014). A multivariable model predicting OS was developed using the training set; the predictive accuracy was assessed in the testing set using time-dependent area under the curve (tAUC). The testing set was stratified based on risk score tertiles (low, intermediate, high), and OS was analyzed using Kaplan-Meier methodology. Results: Demographics, disease characteristics, and OS were balanced between the training and testing sets; median OS was 32.7 months for both datasets. There were no enzalutamide treatment-prognostic factor interactions (predictors). The final multivariable model included 11 prognostic factors: prostate-specific antigen, treatment, hemoglobin, neutrophil-lymphocyte ratio, liver metastases, time from diagnosis to randomization, lactate dehydrogenase, ≥ 10 bone metastases, pain, albumin, and alkaline phosphatase. The tAUC was 0.74 in the testing set. Median (95% confidence interval [CI]) OS for the low-, intermediate-, and high-risk groups (testing set) were not yet reached (NYR) (NYR–NYR), 34.2 months (31.5–NYR), and 21.1 months (17.5–25.0). The hazard ratios (95% CI) for OS in the low- and intermediate-risk groups vs the high-risk group were 0.20 (0.14–0.29) and 0.40 (0.30–0.53), respectively. Conclusions: Our validated prognostic model incorporates factors routinely collected in chemotherapy-naive men with mCRPC treated with enzalutamide and identifies subsets of men with widely differing survival times. Clinical trial information: NCT01212991.

220 Background: A phase 2 study of the androgen receptor inhibitor ENZ as monotherapy in patients with HNPC [NCT01302041] showed a high prostate-specific antigen (PSA) response rate, regardless of baseline metastases, and favorable tolerability. In a 1- and 2-year follow-up, ENZ maintained long-term reductions from baseline in PSA, with minimal impact on total-body bone mineral density (BMD). Herein, results from a pre-specified 3-year follow-up are reported. Methods: A total of67 patients with HNPC and non-castrate testosterone ( ≥ 230 ng/dL) received ENZ 160 mg/day until disease progression or unacceptable toxicity. The primary end point of PSA response ( ≥ 80% decline from baseline) was analyzed at week 25 and 1, 2, and 3 years. Other end points were best overall tumor response, BMD, body composition, quality of life, and safety. Results: At the 3-year visit, 42 (62.7%) patients remained on the study medication. Of those, 38 (90.5%; 95% confidence interval 77.4%, 97.3%) maintained a PSA response. Of the 26 patients with metastases at baseline, 17 (65.4%) had a complete or partial response as best overall response at 3 years. In patients who completed the 3-year visit, minimal changes from baseline were observed in total-body BMD or in BMD of the femoral neck, trochanter, spine L1–L4, or forearm (median and mean changes ranged from –3.6% to 1.3% and –2.7% to –0.1%, respectively). The EORTC QLQ-C30 global health status results showed a small decrease at 3 years versus baseline (–3.96 points), consistent with the 2-year results. At 3 years, measurements for total body fat increased (median, 14.7%; mean, 16.5%) and total body lean decreased (median, –6.3%; mean, –6.5%) from baseline. Physical functioning, fatigue, and dyspnea worsened ( > 10 points) at 3 years, similar to results at 2 years. The most frequently reported adverse events ( > 10%) were gynecomastia, fatigue, hot flush, nipple pain, hypertension, diarrhea, nausea, pain in extremity, back pain, and constipation. Conclusions: In patients with HNPC treated with ENZ for 3 years, the efficacy of ENZ as monotherapy was maintained. Overall, BMD, global health status, and safety results were similar to those at 2 years. Clinical trial information: NCT01302041.

138 Background: Prognostic models require updating to reflect contemporary medical practice. In a post hoc analysis of the phase 3 PREVAIL trial (enzalutamide vs placebo), we identified prognostic factors for overall survival (OS) in chemotherapy-naïve men with mCRPC. Methods: Patients were randomly divided 2:1 into training (n = 1159) and testing (n = 550) sets. Using the training set, 23 predefined candidate prognostic factors (including treatment) were analyzed in a multivariable Cox model with stepwise procedures and in a penalized Cox proportional hazards model using the adaptive least absolute shrinkage and selection operator (LASSO) penalty (data cutoff June 1, 2014). A multivariable model predicting OS was developed using the training set; the predictive accuracy was assessed in the testing set using time-dependent area under the curve (tAUC). The testing set was stratified based on risk score tertiles (low, intermediate, high), and OS was analyzed using Kaplan-Meier methodology. Results: Demographics, disease characteristics, and OS were balanced between the training and testing sets; median OS was 32.7 months for both datasets. There were no enzalutamide treatment-prognostic factor interactions (predictors). The final multivariable model included 11 prognostic factors: prostate-specific antigen, treatment, hemoglobin, neutrophil-lymphocyte ratio, liver metastases, time from diagnosis to randomization, lactate dehydrogenase, ≥ 10 bone metastases, pain, albumin, and alkaline phosphatase. The tAUC was 0.74 in the testing set. Median (95% confidence interval [CI]) OS for the low-, intermediate-, and high-risk groups (testing set) were not yet reached (NYR) (NYR–NYR), 34.2 months (31.5–NYR), and 21.1 months (17.5–25.0). The hazard ratios (95% CI) for OS in the low- and intermediate-risk groups vs the high-risk group were 0.20 (0.14–0.29) and 0.40 (0.30–0.53), respectively. Conclusions: Our validated prognostic model incorporates factors routinely collected in chemotherapy-naïve men with mCRPC treated with enzalutamide and identifies subsets of men with widely differing survival times.

TPS5088Background: Radium-223 dichloride (Ra-223), a first-in-class alpha-emitting radiopharmaceutical targeting bone metastases (mets), reduced risk of death and delayed time to first symptomatic ...