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Total plasma cell-free DNA (cfDNA) levels were recently shown to be prognostic in two large phase III trials of taxane chemotherapy in metastatic castration-resistant prostate cancer (mCRPC). However, whether cfDNA concentration is predictive of treatment outcomes with androgen receptor pathway inhibitors (ARPIs) is unknown. We quantified plasma cfDNA levels at baseline (n = 74) and 4 weeks on treatment (n = 56) in a prospective cohort of mCRPC patients treated with the ARPIs abiraterone acetate or enzalutamide. Elevated total cfDNA concentration (log10) at both baseline (hazard ratio [HR] 5.5, p < 0.001) and week 4 (HR 7.5, p < 0.001) was a significant negative prognostic factor for overall survival (OS), a finding maintained after adjustment for plasma circulating tumour DNA fraction. Unexpectedly, a rise in cfDNA concentration from baseline to week 4 was also associated with significantly improved OS (HR 0.14, p = 0.003). Conversely, patients with >=29.8% decrease in cfDNA from baseline (optimal cut-point) had significantly shorter median OS than the rest of the cohort (10.5 vs 25.7 mo, p = 0.03). Collectively, our findings point to the potential prognostic utility of quantifying cfDNA in mCRPC and in particular suggest that dynamic changes in total cfDNA levels may be a novel early predictive biomarker for therapeutic outcome in ARPI-treated patients. Patient Summary: We measured the levels of total cell-free DNA (cfDNA) in the plasma of patients with metastatic prostate cancer prior to and 4 weeks after starting new hormonal drugs. We found that patients with higher levels of cfDNA or a higher proportion of tumour-derived DNA at baseline had worse outcomes on hormonal therapies. Similarly, higher levels of cfDNA at 4 weeks into therapy were also associated with worse outcomes. However, a rise in total cfDNA levels at 4 weeks compared with baseline was linked with better outcomes. Measuring changes in cfDNA concentration may be a useful and technically straightf

Background: The prognostic significance of DDR alterations in mCRPC remains unclear, with conflicting data from prior reports. Whether DDR alterations are predictive of outcomes with therapeutic agents other than PARP inhibitors in mCRPC is also poorly understood. With increasing use of molecular profiling in mCRPC, understanding the full prognostic and predictive utility of plasma DDR alterations is paramount. Method(s): A next-generation sequencing Predicine liquid biopsy assay was used to profile cfDNA and germline DNA in 407 mCRPC patients (pts) from two independent international cohorts (n=162 Australia, n=245 US). DDR genes profiled were BRCA2, ATM, BRCA1, MLH1 and MSH2. Kaplan-Meier survival estimates and multivariable Cox regression analyses were used to assess associations between DDR alterations and clinical outcomes including PSA response rate (PSA RR), progression-free survival and overall survival (OS). Result(s): Median age was 74 (IQR 67-79), with median follow up 74 months and median OS 23 months. 65/407 (16%) harboured pathogenic DDR alterations, including 21 patients with 1 alteration. Frequency of genomic aberrations are shown in the table. BRCA2 alterations were further classified as heterozygous loss (66%), homozygous loss (14%), monoallelic mutation (11%) and biallelic mutation/loss of heterozygosity (9%). Aberrations in any DDR gene, ATM, MLH1 + MSH2 or BRCA2 were associated with shorter OS on univariable analysis, but only any DDR or BRCA2 aberration remained significant upon adjusting for clinical prognosticators and ctDNA fraction (Table). Pre-treatment BRCA2 aberration was associated with significantly shorter OS and lower PSA RR compared to BRCA2 wt for pts receiving an AR pathway inhibitor (ARPI) (18 vs 32 months, p=0.006; 36 vs 60%, p=0.04 respectively) but not for taxane chemotherapy (17 vs 20 months, p=0.3; 45 vs 66, p=0.1 respectively). Conclusion(s): Detection of an aberration in any DDR gene or BRCA2 was an independent poor prognos

Background: Both changes in circulating lipids represented by a validated poor prognostic 3-lipid signature (3LS) and somatic tumour genetic aberrations are individually associated with worse clinical outcomes in men with metastatic castration-resistant prostate cancer (mCRPC). A key question is how the lipid environment and the cancer genome are interrelated in order to exploit this therapeutically. We assessed the association between the poor prognostic 3-lipid signature (3LS), somatic genetic aberrations and clinical outcomes in mCRPC. Method(s): We performed plasma lipidomic analysis and cell-free DNA (cfDNA) sequencing on 106 men with mCRPC commencing docetaxel, cabazitaxel, abiraterone or enzalutamide (discovery cohort) and 94 men with mCRPC commencing docetaxel (validation cohort). Differences in lipid levels between men +/- somatic genetic aberrations were assessed with t-tests. Associations between the 3LS and genetic aberrations with overall survival (OS) were examined using Kaplan-Meier methods and Cox proportional hazard models. Result(s): The 3LS was associated with shorter OS in the discovery (hazard ratio [HR] 2.15, 95% confidence interval [CI] 1.4-3.3, p < 0.001) and validation cohorts (HR 2.32, 95% CI 1.59-3.38, p < 0.001). Elevated plasma sphingolipids were associated with AR, TP53, RB1 and PI3K aberrations (p < 0.05). Men with both the 3LS and aberrations in AR, TP53, RB1 or PI3K had shorter OS than men with neither in both cohorts (p <= 0.001). The presence of 3LS and/or genetic aberration was independently associated with shorter OS for men with AR, TP53, RB1 and PI3K aberrations (p < 0.02). Furthermore, aggressive-variant prostate cancer (AVPC), defined as 2 or more aberrations in TP53, RB1 and/or PTEN, was associated with elevated sphingolipids. The combination of AVPC and 3LS predicted for a median survival of ~12 months. The relatively small sample size of the cohorts limits clinical applicability and warrants future studies. Conclusion(s)

Background: With the evolving use of targeted therapies exploiting genomic vulnerabilities in mCRPC, screening patients for sensitizing alterations is of increasing relevance. However, the influence of age on the detection of relevant genomic alterations is incompletely understood. In this study, we compared the cell-free DNA (cfDNA) profiles of younger (age <70) versus older (age >=70) men with mCRPC and assessed the relative prognostic impact of common genomic alterations. Method(s): A next-generation sequencing-based Predicine cfDNA assay was used to profile 276 mCRPC patients from two independent international cohorts. The frequency of genomic alterations across age categories was compared using the chi-squared test, while circulating tumour DNA fraction (ctDNA%) was compared using the Mann-Whitney U test. Cox proportional hazards analysis with interaction testing was used to assess the association between age, genomic alteration and overall survival. Result(s): The median age of the combined cohort was 72 years (IQR 66-78), with 170 (62%) patients >=70 years old. Despite differences in baseline characteristics (poorer performance status in older patients, higher Gleason score and de novo metastatic disease in younger patients), there was no significant difference in ctDNA% (median 22% vs 30%, p=0.6). We observed similar frequencies of genomic alterations across the 10 most commonly aberrant genes, including AR (<70 vs >=70: 46% vs 49%, p=0.6), TP53 (40% vs 36%, p=0.6), BRCA2 (29% vs 21%, p=0.13) and PTEN (39% vs 35%, p=0.5). This similarity persisted when analysing mutations and copy number alterations in isolation. While driver alterations in both age categories were strongly associated with unfavourable outcomes (Table), an exploratory analysis revealed that copy number gain in PIK3CA may have a worse prognostic impact in younger men (p for interaction = 0.03), with a lesser effect observed in AR gain (p = 0.1) and MYC gain (p = 0.1). Conclusion(s): The genom

Background: Deleterious alterations in tumor suppressor genes (TSGs) TP53, RB1, and PTEN are potential markers of small cell neuroendocrine prostate cancer (SCNP), and androgen receptor pathway inhibitor (ARPI) resistance. We examined the outcomes and clinical features of mCRPC patients (pts) harboring biallelic loss in 0, 1, 2 or all 3 TSGs. Method(s): We identified 210 consecutive mCRPC pts providing >=1 plasma cell-free DNA sample with >=20% circulating tumor DNA fraction (ctDNA%) during their mCRPC disease course. ctDNA% >=20% enabled sensitive characterization of biallelic TSG loss (including by homozygous deletions and mutation plus somatic loss-of-heterozygosity; LOH). Patient records were reviewed for baseline characteristics, SCNP histology, and presence of liver metastases. We investigated associations between TSG loss and the following clinical outcomes: PSA response (PSA decline >=50% (PSA50 RR)), progression free survival (PFS) on 1L therapy, and overall survival (OS) from 1L therapy. Result(s): Median follow-up was 16.5 months (range: 0.4-112.4) and OS event rate was 95%. Median age at 1L mCRPC was 71 years (range: 48-98). Most pts were ECOG PS 0-1 (79%) and 13% had liver metastases. 91% received ARPI for 1L mCRPC and 7% received ARPI for castration-sensitive disease. TP53 was primarily inactivated by somatic mutation plus LOH (90%), whereas RB1 (71%) and PTEN (86%) were more commonly inactivated by homozygous deletions. Compared to pts without evidence of biallelic TSG loss, pts with loss of 3 TSGs were significantly enriched for de-novo M1 disease (86 vs. 60%, p=0.05) and liver metastases (28.5 vs. 6.8%, p<0.05). Ten pts (4.7%) had histologically confirmed SCNP and provided ctDNA at time of SCNP diagnosis. Of these, 7 (70%) had biallelic loss of >=2 TSGs. For all pts receiving 1L therapy, loss of >=1 TSG(s) was associated with decreased OS (HR: 1.86, 95% CI: 1.40-2.48, p<0.01) and PFS (HR:1.74, 95% CI 1.29-2.34, p<0.01) compared to pts with no bialle

Background: Intrinsic resistance to androgen receptor signalling inhibitors (ARSI) occurs in 20-30% of men with metastatic castration-resistant prostate cancer (mCRPC). Ceramide metabolism may have a role in ARSI resistance. Our study's aim is to investigate the association of the ceramide-sphingosine-1-phosphate (ceramide-S1P) signalling axis with ARSI resistance in mCRPC. Method(s): Lipidomic analysis (~700 lipids) was performed on plasma collected from 132 men with mCRPC, before commencing enzalutamide or abiraterone. AR gene aberrations in 77 of these men were identified by deep sequencing of circulating tumour DNA. Associations between circulating lipids, radiological progression-free survival (rPFS) and overall survival (OS) were examined by Cox regression. Inhibition of ceramide-S1P signalling with sphingosine kinase (SPHK) inhibitors (PF-543 and ABC294640) on enzalutamide efficacy was investigated with in vitro assays, and transcriptomic and lipidomic analyses of prostate cancer (PC) cell lines (LNCaP, C42B, 22Rv1). Finding(s): Men with elevated circulating ceramide levels had shorter rPFS (HR=2.3, 95% CI=1.5-3.6, p = 0.0004) and shorter OS (HR=2.3, 95% CI=1.4-36, p = 0.0005). The combined presence of an AR aberration with elevated ceramide levels conferred a worse prognosis than the presence of only one or none of these characteristics (median rPFS time = 3.9 vs 8.3 vs 17.7 months; median OS time = 8.9 vs 19.8 vs 34.4 months). SPHK inhibitors enhanced enzalutamide efficacy in PC cell lines. Transcriptomic and lipidomic analyses indicated that enzalutamide combined with SPHK inhibition enhanced PC cell death by SREBP-induced lipotoxicity. Interpretation(s): Ceramide-S1P signalling promotes ARSI resistance, which can be reversed with SPHK inhibitors.Copyright © 2021 The Authors

Background: Tumour tissue from metastatic castration-resistant prostate cancer (mCRPC) harbors frequent copy number variations (CNVs) in the phosphatidylinositol-3-kinase (PI3K)/Aktsignaling pathway. However, identifying CNVs in plasma cell-free DNA (cfDNA) has proven challenging. With emerging data supporting Akt inhibition in PTEN-deficient mCRPC, cfDNA assays for robustly identifying PI3K/Akt pathway aberrations including CNVs are urgently required. Method(s): In this multi-institutional prospective biomarker study, we used the Predicine cfDNA assay, optimised for CNV detection, to perform targeted sequencing in 231 mCRPC patients in two independent cohorts (Australian, n = 78; US, n = 153). Kaplan-Meier survival estimates and multivariable Cox regression analysis were used to assess associations between genomic aberrations and progression-free survival (PFS) and overall survival (OS). Result(s): PTEN loss and PIK3CAgain were detected in 37% (85/231) and 17% (39/231) of patients, respectively. Poorer outcomes were observed in patients with PI3K/Akt pathway aberrations, including those with dual PTEN loss and PIK3CA gain (HR 2.3, 95% CI 1.2-4.4). Similarly, cumulative CNV burden in the PI3K/Akt and AR pathways (0 vs 1 vs >=2 CNVs in Australian cohort: median OS 33.5 vs 17.2 vs 9.7 months, p< 0.001; 0 vs 1 vs >=2 CNVs in US cohort: median OS 35.5 vs 14.3 vs 9.2 months, p< 0.001) was associated with significantly worse clinical outcomes. Notably, 21% (31/146) of PTEN-neutral patients harbored other alterations in the PI3K/Akt pathway. Conclusion(s): Our cfDNA assay readily detected PI3K/Akt pathway CNVs, with the prevalence of PTEN loss comparable to prior tissue sequencing studies. CNVs in the PI3K/Akt pathway were associated with deleterious clinical outcomes, especially when concurrent with AR gain. Additional PI3K/Akt pathway aberrations were found in approximately one-fifth of PTEN-neutral mCRPC. Collectively, our data demonstrate the potential utility of profi

Objective: As indications for immune checkpoint inhibitors continue to expand, it is imperative that healthcare professionals across all medical disciplines become familiar with immune-related adverse events (irAE).Herein, we describe the design and implementation of an education program aimed at raising awareness of irAEs across our multisite hospital network. Method(s): Following focus group meetings to determine the optimal design and content of the education program, a one-hour presentation was created to meet the specific learning objectives of the target audience. The program was delivered to three groups: Emergency Department specialist registrars, Clinical Trials Centre nursing staff and junior medical officers. Participants were assessed before and immediately after the presentation using case-based multiple-choice questions via the game-based learning platform, Kahoot . Data were collected regarding percentage of questions answered correctly and total response time. Result(s): Ninety participants were involved in three education sessions. In all three groups there was a higher percentage of questions answered correctly in the post-presentation quiz. Emergency Department specialist registrars answered 29% correctly in the pretest compared to 95% in the post-test. Clinical Trial Centre nursing staff improved from 49% to 89%, respectively. The junior medical officer cohort improved from 33% to 77%, respectively. Therewas a significant improvement in the response speed in the pre-presentation quiz (mean 16 s, SD 0.8) compared to post-presentation quiz (mean 6 s, SD 2.0); t(2)12.4, CI 6.9-14.2, P = .006. Conclusion(s): In this pilot program, an educational program focused on irAEs demonstrated real-time improvement in knowledge base of attendees from a broad range of healthcare disciplines. Future directions include longer term follow-up and expansion to other disciplines (intensive care, radiation oncology). Educational programs of the nature described here wi

Context: Optimal treatment sequencing of abiraterone and enzalutamide in chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC) is challenging. Real-world data (RWD) allow a better understanding of health economic implications in the real world. Objective(s): To determine survival and cost outcomes for two real-world treatment sequences, comparing abiraterone to enzalutamide (AA -> ENZ) with enzalutamide to abiraterone (ENZ -> AA). Evidence Acquisition: A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Searches were performed in Medline, Embase, and Web of Science. Evidence Synthesis: Seventeen studies met our inclusion criteria. Of studies with survival outcomes, 10 featured AA -> ENZ treatment sequences (n = 575), four ENZ -> AA sequences (n = 205), and three both sequences. Better survival outcomes were demonstrated in the AA -> ENZ cohorts in several studies reporting prostate-specific antigen (PSA) progression-free survival (PSA-PFS), combined PSA-PFS, and PSA decline >=50%. Three studies showed shorter treatment duration in cohorts receiving second-line enzalutamide compared with abiraterone. Collectively, six RWD costing studies described patients with mCRPC who experienced treatment with enzalutamide (n = 4195), abiraterone (n = 10 372), AA -> ENZ (n = 443), and ENZ -> AA (n = 91). No study estimated the cost of treatment sequencing of AA -> ENZ or ENZ -> AA. Conclusion(s): No head-to-head studies were found, but we hypothesise that the AA -> ENZ sequence may be less costly than ENZ -> AA, because time on treatment tends to be longer for a first-line treatment and abiraterone is less costly than enzalutamide. There are indications that PFS of AA -> ENZ is superior to that of ENZ -> AA, which supports the former sequence as more cost-effective. Patient Summary: Better survival outcomes were reported in several studies where patients with advanced prosta

Circulating lipids or cytokines are associated with prognosis in metastatic castration-resistant prostate cancer (mCRPC). This study aimed to understand the interactions between lipid metabolism and immune response in mCRPC by investigating the relationship between the plasma lipidome and cytokines. Plasma samples from two independent cohorts of men with mCRPC (n = 146, 139) having life-prolonging treatments were subjected to lipidomic and cytokine profiling (290, 763 lipids; 40 cytokines). Higher baseline levels of sphingolipids, including ceramides, were consistently associated with shorter overall survival in both cohorts, whereas the associations of cytokines with overall survival were inconsistent. Increasing levels of IL6, IL8, CXCL16, MPIF1, and YKL40 correlated with increasing levels of ceramide in both cohorts. Men with a poor prognostic 3- lipid signature at baseline had a shorter time to radiographic progression (poorer treatment response) if their lipid profile at progression was similar to that at baseline, or their cytokine profile at progression differed to that at baseline. In conclusion, baseline levels of circulating lipids were more consistent as prognostic biomarkers than cytokines. The correlation between circulating ceramides and cytokines suggests the regulation of immune responses by ceramides. The association of treatment response with the change in lipid profiles warrants further research into metabolic interventions.Copyright © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Background: We previously identified that elevated circulating ceramides and a validated 3-lipid signature are associated with shorter overall survival (OS) in men with mCRPC. Several somatic gene aberrations in mCRPC are also linked to worse outcomes. This study examines the combined impact of a poor prognostic lipid profile and somatic aberrations on clinical outcomes in mCRPC. Method(s): Plasma lipidomic profiling of >700 lipids and deep targeted sequencing of circulating cell-free DNA was performed on (1) discovery cohort of 121 men with mCRPC starting taxanes or androgen receptor signalling inhibitors and (2) validation cohort of 69 men with mCRPC starting chemotherapy. Associations with radiological progression-free survival (rPFS) and OS were examined. Result(s): The 3-lipid signature was associated with shorter rPFS (HR 1.6, 95% CI 1.0-2.4, p=0.037) and OS (HR 1.9, 95% CI 1.3-2.9, p=0.001) in the discovery cohort and shorter OS (HR 2.3, 95% CI 1.6-3.4, p<0.001) in the validation cohort. In both cohorts, elevated ceramides were correlated with gene aberrations in AR, cell cycle and PI3K pathway (p<0.05). Men with both AR aberrations and 3-lipid signature had worse OS than men with either characteristic (median OS 12.5 vs 21.6m, p=0.005). This was also seen in men with PI3K aberrations (median OS 11.9 vs 21.8m, p=0.003), suggesting an additive effect. The biomarker combination of 3-lipid signature and genetic aberration was independently associated with worse rPFS +/- OS in multivariable analysis with clinicopathologic factors (see the table). The C-index for OS prediction using the Halabi model was improved by addition of the biomarker combination (see the table). [Formula presented] Conclusion(s): Elevated ceramides are associated with AR, cell cycle and PI3K pathway aberrations in mCRPC, and the combination of lipid and gene abnormalities confer a poorer prognosis. This suggests that targeting lipid metabolism in addition to actionable genetic mutations may

Background: Immune checkpoint inhibitor monotherapy in metastatic castration-resistant prostate cancer (mCRPC) has produced modest results. High-dose radiotherapy may be synergistic with checkpoint inhibitors. Objective(s): To evaluate the efficacy and safety of the PD-L1 inhibitor avelumab with stereotactic ablative body radiotherapy (SABR) in mCRPC. Design, setting, and participants: From November 2017 to July 2019, this prospective phase 2 study enrolled 31 men with progressive mCRPC after at least one prior androgen receptor-directed therapy. Median follow-up was 18.0 mo. Intervention(s): Avelumab 10 mg/kg intravenously every 2 wk for 24 wk (12 cycles). A single fraction of SABR (20 Gy) was administered to one or two disease sites within 5 d before the first and second avelumab treatments. Outcomes measurements and statistical analysis: The primary endpoint was the disease control rate (DCR), defined as a confirmed complete or partial response of any duration, or stable disease/non-complete response/non-progressive disease for >=6 mo (Prostate Cancer Clinical Trials Working Group 3-modified Response Evaluation Criteria in Solid Tumours version 1.1). Secondary endpoints were the objective response rate (ORR), radiographic progression-free survival (rPFS), overall survival (OS), and safety. DCR and ORR were calculated using the Clopper-Pearson exact binomial method. Results and limitations: Thirty-one evaluable men were enrolled (median age 71 yr, 71% with >=2 prior mCRPC therapy lines, 81% with >5 total metastases). The DCR was 48% (15/31; 95% confidence interval [CI] 30-67%) and ORR was 31% (five of 16; 95% CI 11-59%). The ORR in nonirradiated lesions was 33% (four of 12; 95% CI 10-65%). Median rPFS was 8.4 mo (95% CI 4.5-not reached [NR]) and median OS was 14.1 mo (95% CI 8.9-NR). Grade 3-4 treatment-related adverse events occurred in six patients (16%), with three (10%) requiring high-dose corticosteroid therapy. Plasma androgen receptor alterations were assoc

Objectives: To investigate the recent real-world use of first-generation antiandrogens (FGAs) in metastatic castration-resistant prostate cancer (mCRPC) using a retrospective multicentre cohort study. Patients and Methods: The electronic CRPC Australian Database (ePAD) was interrogated to identify patients with mCRPC. Clinicopathological features, treatment and outcome data, stratified by FGA use, were retrieved and reported through descriptive statistics. Survival analyses were calculated using the Kaplan-Meier method and groups compared using log-rank tests. Factors influencing overall survival (OS) were analysed using Cox proportional hazards regression model. Result(s): We identified 634 patients with mCRPC, enrolled in ePAD between January 2016 and March 2019, including 322 (51%) who received FGAs. The median follow-up was 21.9 months. Patients treated with FGAs were more likely to have lower International Society of Urological Pathologists (ISUP) grade group (P = 0.04), longer median time to CRPC (25.6 vs 16.0 months, P < 0.001), and were less likely to have visceral metastases (5.0% vs 11.2%, P = 0.005) or to have received upfront docetaxel (P < 0.001). A >=50% reduction from pre-treatment prostate-specific antigen (PSA) level (PSA50 response) during FGA treatment occurred in 119 (37%) patients and was independently associated with improved OS (hazard ratio 0.233, P < 0.001). Prior FGA treatment did not significantly influence the selection of subsequent life-prolonging treatments for mCRPC or their PSA50 response rates. Conclusion(s): In our present cohort, FGAs were commonly used in lower-risk mCRPC and their use did not significantly influence the choice or duration of subsequent systemic therapy. A PSA50 response to FGA therapy was an independent favourable prognostic marker associated with improved OS.Copyright © 2021 The Authors. BJU International © 2021 BJU International

Background: As potent systemic therapies transition earlier in the prostate cancer disease course, molecular biomarkers are needed to guide optimal treatment selection for metastatic hormone-sensitive prostate cancer (mHSPC). The value of whole blood RNA to detect candidate biomarkers in mHSPC remains largely undefined. Method(s): In this cohort study, we used a previously optimised whole blood reverse transcription polymerase chain reaction assay to assess the prognostic utility [measured by seven-month undetectable prostate-specific antigen (PSA) and time to castration-resistance (TTCR)] of eight prostate cancer-associated gene transcripts in 43 mHSPC patients. Transcripts with statistically significant associations (P<0.05) were further investigated in a metastatic castration-resistant prostate cancer (mCRPC) cohort (n=119) receiving contemporary systemic therapy, exploring associations with PSA >50% response (PSA50), progression-free survival (PFS) and overall survival (OS). Clinical outcomes were prospectively collected in a protected digital database. Kaplan-Meier estimates and multivariable Cox proportional-hazards models assessed associations between gene transcripts and clinical outcomes (mHSPC covariates: disease volume, docetaxel use and haemoglobin level; mCRPC covariates: prior exposure to chemotherapy or ARPIs, haemoglobin, performance status and presence of visceral disease). Follow-up was performed monthly during ARPI treatment, three-weekly during taxane chemotherapy, and three-monthly during androgen deprivation therapy (ADT) monotherapy. Serial PSA measurements were performed before each follow-up visit and repeat imaging was at the discretion of the investigator. Result(s): Detection of circulating Grainyhead-like 2 (GRHL2) transcript was associated with poor outcomes in mHSPC and mCRPC patients. Detectable GRHL2 expression in mHSPC was associated with a lower rate of seven-month undetectable PSA levels (25% vs. 65%, P=0.059), and independently a

Background: Studies investigating immune checkpoint inhibitors (ICI) in mCRPC have produced modest results. Radiation therapy may be synergistic with ICIs. We hypothesised that SABR would enhance anti-tumour activity of PD-L1 inhibitor avelumab in patients (pts) with progressive mCRPC. Method(s): This phase II, single arm, multicentre study enrolled mCRPC pts following progression on >=1 novel androgen receptor-directed therapy. Up to two lines of prior taxane chemotherapy were permitted. Pts received avelumab 10mg/kg IV q2weeks for a total of 24 weeks (12 cycles). A single fraction of 20Gy SABR was administered to 1-2 disease sites within five days prior to first and second doses of avelumab. Primary endpoint was disease control rate (DCR); secondary endpoints were PSA response (PSA ), overall response rate (ORR), radiographic progression-free survival (rPFS), overall survival (OS) and safety. Radiographic disease assessment (CT and bone scintigraphy) was performed after cycles 6 and 12 of avelumab treatment. Following enrolment of 14 pts, a protocol amendment allowed avelumab beyond 12 cycles in pts with disease control at 24 weeks. Result(s): Thirty-one pts were enrolled, with 30 evaluable for the primary endpoint. Median follow-up was 18 months (mo). Pt characteristics: median age 71 years (IQR 64-75), bone-only disease 42%, visceral disease 16%, prior taxane chemotherapy 84%, treatment with both abiraterone and enzalutamide 13%. Seventy metastatic sites received SABR, most frequently to bone (90%) and soft tissue (29%) disease. Avelumab was given as second-line, third-line and fourth- or greater line systemic therapy in 29%, 42% and 29% of pts, respectively. Median cycles of avelumab administered was 9 (IQR 5-13). DCR (95% CI) was 50% (31-69) and 60% (32-84) in allcomers and soft tissue disease subgroup, respectively. Following protocol amendment, 7/17 pts (41%) received avelumab beyond 12 cycles. Incidence of grade 3-4 treatment-related AEs was 16% (no grade 5

Aims: Prostate-specific membrane antigen (PSMA) PET/CT has emerged as the optimal imaging modality to detect recurrent prostate cancer in patients with biochemical relapse (BCR) following curative intent treatment. However, its impact on clinical decision making in the era of metastasis-directed therapy remains unclear. This study aims to explore the role of PSMA PET/CT on clinical decisionmaking in patients with BCR following definitive therapy. Method(s): We prospectively enrolled 40 patients with BCR to undergo 68Ga-PSMA PET/CT. Baseline clinicopathological factors were obtained and referring clinicians documented their proposed treatment plan both prior to and following imaging. Changes in clinical management were considered to have clinical impact. Result(s): 68Ga-PSMA PET/CT detected at least one suspicious lesion in 23/40 (58%) patients, with a median PSA level of 0.59 mug/L (IQR 0.21- 2.31). Positive scansweremore frequent at higher PSA levels (P<.001, Fischer's exact test). The most common sites of PSMA-avid disease were lymph nodes (61%) and bone (30%). Lymph node involvement was typically pelvic nodes (13/14, 93%). Bone involvement was mostly outside the axial skeleton (5/7, 71%). PSMA PET/CT altered management in 21/40 (53%) patients. Of those planned for watchful waiting, 14/24 (58%) proceeded to amore activemanagement strategy, including salvage radiotherapy (n = 6), stereotactic ablative body radiotherapy (SABR; n = 5), androgen deprivation therapy (n = 2) and salvage surgery (n = 1). Conclusion(s): 68Ga-PSMA PET/CT altered management strategy in a significant proportion of prostate cancer patients with BCR following definitive therapy. Our data demonstrate a shift from planned watchful waiting to more active treatment in over half patients with a positive 68Ga-PSMA PET/CT. Longer-term follow-up is required to assess the influence of such strategies on clinical outcomes.

Context: Multiple studies have reported on the genomic characteristics of metastatic hormone-sensitive prostate cancer (mHSPC). The impact of these findings on prognostication, treatment selection, and clinical trial design remains unclear. Objective(s): To summarise genomic alteration prevalences in liquid and/or tissue biopsies, infer their clinical implications, and compare genomic alteration frequencies across different disease states and clinical phenotypes. Evidence Acquisition: The PubMed and Web of Knowledge databases were systematically searched up to January 2021. Quality assessment was performed using the Joanna Briggs Institute Critical Appraisal tools. Evidence Synthesis: In total, 11 studies encompassing 1682 mHSPC patients were included. High-volume disease was associated with more frequent alterations in TP53, DNA damage repair, and Wnt pathways. Tumours from patients with de novo mHSPC were enriched for alterations in TP53 and CDK12 compared with recurrent disease. Alterations in AR, TP53, cell cycle signalling, and MYC were associated with a poorer clinical outcome. A comparative analysis of gene alteration frequencies across disease states revealed a relative increase from localised to castration-resistant tumours, with noteworthy enrichment of CTNNB1 alterations in mHSPC (5%), which warrants further investigation. This study was limited by variability in methodology and definitions used among the eligible studies, including differences in sequencing methods, analytes (being either tissue or liquid), alteration calling thresholds, and target patient populations with a relative under-representation of recurrent metastatic disease. Conclusion(s): Several genomic alterations are associated with differential prognosis and clinical phenotypes in mHSPC. We urge that emerging data on these potential predictive biomarkers must be validated in biomarker-driven randomised controlled trials before any clinical implementation. Alignment of the assay methodolo

Preclinical testing is a crucial step in evaluating cancer therapeutics. We aimed to establish a significant resource of patient-derived xenografts (PDXs) of prostate cancer for rapid and systematic evaluation of candidate therapies. The PDX collection comprises 59 tumors collected from 30 patients between 2012-2020, coinciding with availability of abiraterone and enzalutamide. The PDXs represent the clinico-pathological and genomic spectrum of prostate cancer, from treatment-naive primary tumors to castration-resistant metastases. Inter- and intra-tumor heterogeneity in adenocarcinoma and neuroendocrine phenotypes is evident from bulk and single-cell RNA sequencing data. Organoids can be cultured from PDXs, providing further capabilities for preclinical studies. Using a 1 x 1 x 1 design, we rapidly identify tumors with exceptional responses to combination treatments. To govern the distribution of PDXs, we formed the Melbourne Urological Research Alliance (MURAL). This PDX collection is a substantial resource, expanding the capacity to test and prioritize effective treatments for prospective clinical trials in prostate cancer.Copyright © 2021, The Author(s).

Background: LuPSMA - 617 is a promising therapy for metastatic castrate-resistant prostate cancer (mCRPC). However, treatment resistance occurs frequently and synergistic combination therapy may improve outcomes. We combined LuPSMA - 617 with idronoxil (NOX66), an inhibitor of external NADH oxidase type 2 with radio-sensitizing properties. We present the final safety and efficacy results. Method(s): Men with progressive mCRPC after androgen signalling inhibition (ASI) and taxane chemotherapy were enrolled. Key inclusion criteria were: PSMA PET/CT intensity SUV max > 15 with no discordant disease on FDG PET/CT, haemoglobin > 100g/L, platelets > 100x10 /L and eGFR > 40mls/min. Enrolled patients received up to six doses of Lu-PSMA 617 (7.5Gbq) day 1 every 6 weeks in combination with NOX66 days 1-10 each cycle. Cohort 1 (n = 8) received 400mg NOX66. Following safety reviews the doses were escalated in cohorts 2 (n = 24) and 3 (n = 24) to 800mg and 1200mg of NOX66, respectively. Blood samples were prospectively collected for androgen receptor splice variant 7 (ARV7) expression. PSMA and FDG PET/CT were performed at study entry and on progression. The primary outcomes were safety and tolerability; the secondary outcomes evaluated were efficacy, pain scores, and quality of life. Result(s): Of the 56 men enrolled, all had received prior treatment with ASI and docetaxel, and 95% (53/56) had prior cabazitaxel. 96% (54/56) patients received >=2 cycles and 46% (26/56) completed six cycles of treatment. Adverse events are summarized in the table below. PSA responses were as follows: 86% (48/56) had any PSA reduction and 61% (34/56) had > 50% PSA reduction. 84% (47/56) have had PSA progression to date with median follow up 18.9 months (95% CI 11.9-25.8). Median PSA PFS was 7.5 months (95% CI 6.0-9.0). 55% (31/56) have died and median overall survival was 19.7 months (95% CI 10.7-28.7). 34/56 men had baseline pain scores >=3, of whom 53% (18/34) had significant reduction in pain i

Introduction: Bone metastases occur frequently in castration-resistant prostate cancer (CRPC) and may lead to skeletal-related events (SREs), including symptomatic skeletal events (SSEs). Bone-modifying agents (BMAs) delay SREs and SSEs. However, the real-world use of BMAs is debated given the absence of demonstrated survival advantage and potential adverse events (AEs). Our retrospective study examined BMA use and SSE rates in Australian patients with CRPC. Method(s): Patients with CRPC and bone metastases were identified from the electronic CRPC Australian Database. Patient characteristics, treatment patterns and AEs were analysed. Descriptive statistics reported baseline characteristics, SSE rates and BMA use. Comparisons between groups used t-tests and Chi-square analyses. Overall survival was calculated by the Kaplan-Meier method. Result(s): A total of 532 eligible patients were identified with a median age of 73 years (range: 44-97 years). BMAs were prescribed in 232 men (46%), 183 of whom received denosumab. Patients receiving first-line docetaxel for CRPC were more likely to commence BMAs than those receiving abiraterone or enzalutamide (51% vs 31% vs 38%; p = 0.004). SSEs occurred in 148 men (28%), most commonly symptomatic lesions requiring intervention (75%). At the time of initial SSEs, only 28% were receiving BMAs. Patients treated at sites with lower BMA use (

Objective: PSMA PET/CT has demonstrated superior sensitivity over conventional imaging in the detection of local and distant recurrence in biochemically relapsed (BCR) prostate cancer. We prospectively investigated the management impact of 68Ga-PSMA PET/CT imaging in men with BCR, with the aim of identifying baseline clinicopathological predictors for management change. Patients and Methods: Men with BCR who met eligibility criteria underwent 68Ga-PSMA-11 PET/CT at Monash Health (Melbourne, Australia). Intended management plans were prospectively documented before and after 68Ga-PSMA PET/CT imaging. Binary logistic regression analysis was performed to identify potential clinicopathological predictors of management change. Descriptive statistics were used to characterize the nature of these changes. Result(s): Seventy men underwent 68Ga-PSMA-11 PET/CT imaging. Median age was 67 years (IQR 63-72) and median PSA was 0.48 ng/ml (IQR 0.21-1.9). PSMA-avid disease was observed in 56% (39/70) of patients. Pre-scan management plan was altered following scanning in 43% (30/70) of patients. Management changes were significantly more common in patients with higher baseline PSA levels (PSA>=2 ng/ml, p = 0.01). 18/36 (50%) of the patients initially planned for watchful waiting had their management changed, including the use of salvage pelvic radiotherapy (n = 7) and stereotactic ablative body radiotherapy to oligometastatic disease (n = 6). Conclusion(s): Management change after 68Ga-PSMA PET/CT for BCR is common and typically resulted in treatment intensification strategies in those planned for a watchful waiting approach. This study adds to the growing pool of evidence supporting the clinical utility of PSMA PET/CT imaging in the care of patients with BCR after definitive therapy.Copyright © 2021 John Wiley & Sons Australia, Ltd

Background: Lutetium-177 [177Lu]Lu-PSMA-617 is a radiolabelled small molecule that delivers beta radiation to cells expressing prostate-specific membrane antigen (PSMA), with activity and safety in patients with metastatic castration-resistant prostate cancer. We aimed to compare [177Lu]Lu-PSMA-617 with cabazitaxel in patients with metastatic castration-resistant prostate cancer. Method(s): We did this multicentre, unblinded, randomised phase 2 trial at 11 centres in Australia. We recruited men with metastatic castration-resistant prostate cancer for whom cabazitaxel was considered the next appropriate standard treatment. Participants were required to have adequate renal, haematological, and liver function, and an Eastern Cooperative Oncology Group performance status of 0-2. Previous treatment with androgen receptor-directed therapy was allowed. Men underwent gallium-68 [68Ga]Ga-PSMA-11 and 2-flourine-18[18F]fluoro-2-deoxy-D-glucose (FDG) PET-CT scans. PET eligibility criteria for the trial were PSMA-positive disease, and no sites of metastatic disease with discordant FDG-positive and PSMA-negative findings. Men were randomly assigned (1:1) to [177Lu]Lu-PSMA-617 (6.0-8.5 GBq intravenously every 6 weeks for up to six cycles) or cabazitaxel (20 mg/m2 intravenously every 3 weeks for up to ten cycles). The primary endpoint was prostate-specific antigen (PSA) response defined by a reduction of at least 50% from baseline. This trial is registered with ClinicalTrials.gov, NCT03392428. Finding(s): Between Feb 6, 2018, and Sept 3, 2019, we screened 291 men, of whom 200 were eligible on PET imaging. Study treatment was received by 98 (99%) of 99 men randomly assigned to [177Lu]Lu-PSMA-617 versus 85 (84%) of 101 randomly assigned to cabazitaxel. PSA responses were more frequent among men in the [177Lu]Lu-PSMA-617 group than in the cabazitaxel group (65 vs 37 PSA responses; 66% vs 37% by intention to treat; difference 29% (95% CI 16-42; p<0.0001; and 66% vs 44% by treatment rec

Background: Intrinsic resistance to androgen receptor signalling inhibitors (ARSI) such as enzalutamide and abiraterone occurs in 20-30% of men with metastatic castration-resistant prostate cancer (mCRPC), and responders will eventually develop resistance. Epidemiological, lipidomic and molecular studies suggest a role of ceramide metabolism in ARSI resistance. Our study aims to investigate the association of the ceramide-S1P (ceramide-S1P) signalling axis with ARSI resistance in mCRPC. Method(s): Lipidomic analysis (>700 lipids) was performed on plasma samples collected from 132 men with mCRPC before starting enzalutamide or abiraterone. AR gene aberrations were identified by deep sequencing of circulating tumour DNA on a subset of the cohort (n=77). Associations between circulating lipids, AR aberrations, radiological progression-free survival (rPFS) and overall survival (OS) were examined. The effect of inhibiting ceramide-S1P signalling with sphingosine kinase (SPHK) inhibitors (PF-543 & ABC294640) on enzalutamide efficacy was investigated with in vitro assays, and transcriptomic and lipidomic analyses of prostate cancer (PC) cell lines (LNCaP, C42B, 22Rv1). Result(s): Men with a plasma lipidomic profile of elevated levels of ceramides had shorter rPFS (HR 2.3, 95% CI 1.5-3.6, P = 0.0004), shorter OS (HR 2.3, 95% CI 1.4-3.6, P = 0.0005) and a higher frequency of AR aberrations (58% vs 33%, P = 0.04) than those with the opposite profile. The presence of an AR aberration combined with a lipidomic profile of elevated ceramides was associated with a shorter rPFS and OS, than the presence of only one of these characteristics, or none (median rPFS time = 3.9 vs 8.3 vs 17.7 months; median OS time = 8.9 vs 19.8 vs 34.4 months). SPHK inhibitors decreased the IC50 of enzalutamide in PC cell lines by 1.8 to 15 fold (P<0.0008). Transcriptomic and lipidomic analyses indicated that enzalutamide combined with SPHK inhibition enhanced PC cell death by SREBP-induced lipotoxicity

Background: The androgen receptor (AR) pathway-associated gene nuclear receptor coactivator 2 (NCOA2) has an established oncogenic role in early prostate cancer and likewise is a driver of metastatic disease and castration-resistant prostate cancer. However, its significance as a biomarker in metastatic castration-resistant prostate cancer (mCRPC), both alone and in conjunction with co-occurring AR alterations using a liquid biopsy approach has not been investigated. Method(s): Ninety-one patients were included in this study, (n = 68 receiving an androgen receptor pathway inhibitor and n = 23 receiving taxane chemotherapy). Up to 30 ml of peripheral blood was collected before commencing treatment from each patient. Plasma cell-free DNA, along with a matched germline sample, underwent targeted next-generation sequencing using a validated, highly sensitive in-house prostate cancer panel. Variants in AR and NCOA2 were identified and correlated with clinical outcomes. Result(s): Plasma AR and NCOA2 aberrations were identified in 35% and 13% of the cohort, respectively, whilst 8% had concurrent AR and NCOA2 alterations. NCOA2 copy number gain and any NCOA2 aberration predicted for lower prostate-specific antigen (PSA) response rates. Likewise, median overall survival was shorter for NCOA2 gain (10.1 vs. 18.3 months; p =.004), remaining significant after adjusting for covariates including circulating tumor DNA fraction and tumor suppressor gene alterations. Importantly, dual AR and NCOA2 aberrations were also associated with inferior outcomes, including no PSA responses in patients treated with AR pathway inhibitors (0% vs. 64%; p =.02). Conclusion(s): These data highlight the importance of identifying multiple markers of AR pathway modulation in mCRPC and represent the first instance of the assessment of plasma NCOA2 status as a prognostic biomarker for standard-of-care therapies. Further assessment is warranted to determine if NCOA2 aberrations are a marker of primary r

PURPOSE Tumor tissue frommetastatic castration-resistant prostate cancer (mCRPC) harbors frequent copy number variations (CNVs) in the PTEN-PI3K-AKT pathway. However, identifying CNVs in plasma cell-free DNA (cfDNA) has proven to be challenging. With emerging data supporting Akt inhibition in PTEN-deficientmCRPC, we profiled PTENPI3K- AKT pathway aberrations in patients with mCRPC using a novel cfDNA assay optimized for CNV detection. METHODS A next-generation sequencing-based cfDNA assay was used to profile 231 patients with mCRPC from two independent cohorts (Australian, n = 78; United States, n = 153). PTEN-PI3K-AKT pathway genomic aberrations were correlated with clinical outcomes, including progression-free survival and overall survival (OS). RESULTS PTEN loss and PIK3CA gain were detected in 37% (85 of 231) and 17% (39 of 231) of patients, respectively. Poorer outcomes were observed in patients with PTEN-PI3K-AKT pathway aberrations, including those with dual PTEN loss and PIK3CA gain (hazard ratio 2.3, 95% CI 1.2 to 4.4). Cumulative CNV burden in the PTEN-PI3K-AKT and androgen receptor (AR) pathways was associated with significantly worse clinical outcomes (0 v 1 v >= 2 CNVs in Australian cohort: Median OS 33.5 v 17.2 v 9.7 months, P<001; 0 v 1 v >= 2 CNVs in US cohort: Median OS 35.5 v 14.3 v 9.2 months, P <.001). Notably, 21% (31 of 146) of PTEN-neutral patients harbored alternative PTEN-PI3K-AKT pathway aberrations. CONCLUSION PTEN-PI3K-AKT pathway CNVs were readily detected using our cfDNA assay, with the prevalence of PTEN loss comparable with tissue-based studies. Additional PTEN-PI3K-AKT pathway aberrations were found in one fifth of PTEN-neutral cases. Concurrent CNVs in the PTEN-PI3K-AKT and AR pathways portended poor survival, and identifying this high-risk patient subset for dual AR/Akt inhibition may optimize precision treatment with Akt inhibitors in mCRPC.Copyright © 2021 American Society of Clinical Oncology. All rights reserved.

Background: CheckMate 9KD is a phase II, multi-cohort trial of NIVO (anti-PD-1) combined with rucaparib, docetaxel, or enzalutamide for mCRPC. We report results for cohort A2, assessing NIVO + rucaparib for CT-naive mCRPC. Method(s): In cohort A2, unselected patients (pts) with CT-naive mCRPC, ongoing ADT, prior abiraterone and/or enzalutamide for mCRPC, and no prior PARP inhibitors received NIVO 480 mg Q4W + rucaparib 600 mg BID until disease progression/unacceptable toxicity (NIVO dosing <= 2 y). Coprimary endpoints were objective response rate (ORR) per PCWG3 criteria and prostate-specific antigen response rate (PSA-RR) in all treated pts and pts with homologous recombination deficiency positive (HRD+) tumors; HRD status was determined before enrollment. Secondary endpoints included radiographic progression-free survival (rPFS), overall survival (OS), and safety. Result(s): Of 71 treated pts, median age 73 y (range, 51-87 y), 23.9% had visceral metastases and 54.9% had measurable disease. Median treatment duration was 4.6 mo for NIVO and 5.5 mo for rucaparib; median follow-up was 17.5 mo. The table summarizes efficacy results, and shows better outcomes for HRD+ vs HRD-/not evaluable tumors. Any-grade treatment-related AEs (TRAEs) occurred in 90.1% of pts, most commonly nausea (40.8%) and anemia (32.4%). Grade >= 3 TRAEs occurred in 50.7% of pts, most commonly anemia (14.1%) and increased ALT (12.7%). TRAEs led to discontinuation in...Copyright © 2021 European Society for Medical Oncology

Background: DNA originating from degenerate tumour cells can be detected in the circulation in many tumour types, where it can be used as a marker of disease burden as well as to monitor treatment response. Although circulating tumour DNA (ctDNA) measurement has prognostic/predictive value in metastatic prostate cancer, its utility in localised disease is unknown. Method(s): We performed whole-genome sequencing of tumour-normal pairs in eight patients with clinically localised disease undergoing prostatectomy, identifying high confidence genomic aberrations. A bespoke DNA capture and amplification panel against the highest prevalence, highest confidence aberrations for each individual was designed and used to interrogate ctDNA isolated from plasma prospectively obtained pre- and post- (24 h and 6 weeks) surgery. In a separate cohort (n = 189), we identified the presence of ctDNA TP53 mutations in preoperative plasma in a retrospective cohort and determined its association with biochemical- and metastasis-free survival. Result(s): Tumour variants in ctDNA were positively identified pre-treatment in two of eight patients, which in both cases remained detectable postoperatively. Patients with tumour variants in ctDNA had extremely rapid disease recurrence and progression compared to those where variants could not be detected. In terms of aberrations targeted, single nucleotide and structural variants outperformed indels and copy number aberrations. Detection of ctDNA TP53 mutations was associated with a significantly shorter metastasis-free survival (6.2 vs. 9.5 years (HR 2.4; 95% CIs 1.2-4.8, p = 0.014). Conclusion(s): CtDNA is uncommonly detected in localised prostate cancer, but its presence portends more rapidly progressive disease.Copyright © 2020 The Author(s).

Background: The androgen receptor (AR) remains a critical driver in metastatic castration-resistant prostate cancer (mCRPC). Profiling AR aberrations in both circulating DNA and RNA may identify key predictive and/or prognostic biomarkers in the context of contemporary systemic therapy. Objective(s): To profile AR aberrations in circulating nucleic acids and correlate with clinical outcomes. Design, setting, and participants: We prospectively enrolled 67 mCRPC patients commencing AR pathway inhibitors (ARPIs; n = 41) or taxane chemotherapy (n = 26). Using a first-in-class next-generation sequencing-based assay, we performed integrated cell-free DNA (cfDNA) and cell-free RNA (cfRNA) profiling from a single 10 ml blood tube. Outcome measurements and statistical analysis: Kaplan-Meier survival estimates and multivariable Cox regression analyses were used to assess associations between clinical outcomes and the following AR aberrations: copy number variation, splice variants (AR-V7 and AR-V9) and somatic mutations. Results and limitations: Cell-free DNA and cfRNA were successfully sequenced in 67 (100%) and 59 (88%) patients, respectively. Thirty-six (54%) patients had one or more AR aberrations. AR gain and cumulative number of AR aberrations were independently associated with clinical/radiographic progression-free survival (PFS; hazard ratio [HR] 3.2, p = 0.01 and HR 3.0 for 0 vs >=2, p = 0.04) and overall survival (HR 2.8, p = 0.04 and HR 2.9 for 0 vs >=2, p = 0.03). Notably, concurrent AR gain and AR splice variant expression (AR gain/AR-V+) was associated with shorter prostate-specific antigen PFS on both ARPIs (HR 6.7, p = 0.009) and chemotherapy (HR 3.9, p = 0.04). Importantly, key findings were validated in an independent cohort of mCRPC patients (n = 40), including shorter OS in AR gain/AR-V+ disease (HR 3.3, p = 0.02). Limitations include sample size and follow-up period. Conclusion(s): We demonstrate the utility of a novel, multianalyte liquid biopsy assay ca

Background: Multiple tumour tissue studies have demonstrated the prognostic utility of CNVs in mCRPC. However, accurate assessment of CNVs in plasma cfDNA remains challenging, and prognostic significance has not been well characterized. Using a large customized panel, we correlated plasma CNVs with clinical outcomes in a contemporary cohort of mCRPC patients. Method(s): Deep targeted sequencing was performed using a 180-gene cfDNA panel (Predicine) in 56 patients commencing AR pathway inhibitors (enzalutamide or abiraterone; n = 34) or taxane chemotherapy (n = 22) at two Australian institutions. Kaplan-Meier estimates and Cox proportional-hazards models were used to correlate CNVs with progression-free survival (PFS) and overall survival (OS). Significant results were validated in an independent cohort (Mayo Clinic, n = 144). Result(s): Median follow-up was 19.4 months (mo; IQR 11.3-31.9). The most common CNVs in the Australian cohort are shown (Table). OS was significantly decreased in patients with PI3KCA gain (median 21.7 mo vs 6.6 mo, p < 0.0001 ), PTEN loss (24.8 mo vs 11.7 mo, p = 0.0019) and AR gain (21.7 mo vs 12.0 mo, p = 0.0083). Furthermore, all three alterations independently predicted for poor survival in multivariable analyses (MVA; Table). Findings in the independent cohort showed similar OS results in MVA: PIK3CA gain (HR 2.0, p = 0.07), PTEN loss (HR 1.7, p = 0.08) and AR gain (HR 1.7, p = 0.03). Conclusion(s): Sequencing of plasma cfDNA revealed that PTEN loss, and PIK3CA and AR gain are associated with inferior clinical outcomes in patients commencing contemporary systemic treatment. These data support therapeutic strategies co-targeting the PI3K and AR pathways in mCRPC. Covariates in MVA: circulating tumour DNA fraction > 2%, prior treatment, visceral disease, baseline pain and ECOG >2.

INTRODUCTION: The last decade has seen a remarkable shift in the treatment landscape of advanced prostate cancer, none more so than in the management of metastatic castration-naive disease. METHOD(S): This narrative review will examine existing and emerging evidence supporting systemic therapy use for metastatic castration-naive prostate cancer (mCNPC) and provide guidance on the selection of these agents with respect to optimising patient outcomes. RESULT(S): The addition of either docetaxel (chemohormonal approach) or an AR pathway inhibitor (abiraterone, enzalutamide or apalutamide) is a reasonable standard of care option for men commencing long-term ADT for mCNPC. While the issue of disease volume as a predictive biomarker for docetaxel benefit has previously been debated, recent data support consideration of upfront docetaxel in all patients, regardless of metastatic burden. Decisions regarding systemic treatment for men with mCNPC should be based on comprehensive consideration of disease, patient and logistical factors. Multiple novel therapeutics for mCNPC are currently under active investigation. CONCLUSION(S): The introduction of potent systemic therapy earlier in the mCNPC disease course has resulted in dramatic improvements in clinical outcomes for patients. As the management of mCNPC continues to evolve, the future remains promising, with the expectation of ongoing improvements to patient outcomes and quality of life.

Background: Metastatic prostate cancer is a clonally heterogeneous disease state characterized by progressive somatic perturbations. The aim of this study was to identify cell free DNA- (cfDNA-) based alterations and their associations with outcomes in progressive metastatic prostate cancer. Method(s): In this longitudinal prospective cohort study plasma cfDNA/circulating tumor DNA (ctDNA) was analyzed before, during, and after androgen deprivation therapy (ADT) in 4 independent patient groups ranging from untreated metastatic hormone sensitive prostate cancer (mHSPC) to metastatic castrate resistant prostate cancer (mCRPC). Next generation sequencing was performed on ctDNA and germline DNA to characterize alterations and associations with clinical outcomes were determined for each group. Finding(s): cfDNA yields were different in progressive mHSPC and mCRPC states (P < .001). In mHSPC, a higher than median ctDNA fraction was predictive of shorter time to ADT failure (HR, 2.29 [95% CI, 1.13-4.65]; Log-Rank P = .02). cfDNA, ctDNA taken with volume of metastatic disease in mHSPC and with alkaline phosphatase levels prognosticated survival better than clinical factors alone in mHSPC and mCRPC states (Log Rank P = 0.03). ctDNA-based AR, APC mutations were increased in mCRPC compared to mHSPC (P < .05).TP53 mutations, RB1 loss, and AR gene amplifications correlated with poorer survival in mCRPC. Mutations in multiple DNA repair genes (ATM, BRCA1, BRCA2, CHEK2) were associated with time to ADT treatment failure and survival in mHSPC. Interpretation(s): ctDNA fraction can further refine clinical prognostic factors in metastatic prostate cancer. Somatic ctDNA alterations have potential prognostic, predictive, and therapeutic implications in metastatic prostate cancer management. Funding(s): Several funding sources have supported this study. A full list is provided in the Acknowledgments. No funding was received from Predicine, Inc. during the conduct of the study.Copyright

Plasma circulating tumor DNA (ctDNA) analysis has emerged as a minimally invasive means to perform molecular tumor typing. Here we developed a custom ultra-sensitive ctDNA next-generation sequencing assay using molecular barcoding technology and off-the-shelf reagents combined with bioinformatics tools for enhanced ctDNA analysis. Assay performance was assessed via a spike-in experiment and the technique was applied to analyze 41 plasma samples from men with advanced prostate cancer. Orthogonal validation was performed using a commercial assay. Sensitivity and specificity of 93 and 99.5% were recorded for ultra-rare somatic variants (<1%), with high concordance observed between the in-house and commercial assays. The optimized protocol dramatically improved the efficiency of the assay and enabled the detection of low-frequency somatic variants from plasma cell-free DNA (cfDNA).Copyright © 2020 Arun Azad.

Background: There is no prospective data to guide optimal selection of treatment for first line (1L) mCRPC after D and androgen deprivation therapy (ADT) is given in the hormone sensitive setting. We explored efficacy of 1L treatment in this group. Method(s): Pts with mCRPC treated with D for hormone sensitive disease were identified from a prospectively maintained multi-site mCRPC database (ePAD) of patients treated in a community and academic setting in Australia. 1L treatment, clinicopathologic and outcome data were extracted. Result(s): We identified 93 pts, median age 65y (range 43-85), who received median 6 cycles of D-ADT and developed mCRPC between May 2013 and Jun 2019. 58% had Gleason > 8, median PSA at diagnosis was 53 ng/mL (range 0.67-7086), 65% had de-novo metastatic disease. Median time to mCRPC was 14.8mo (range 1.3 to 56.9) with median time to 1L 16.3mo (range 2.1-57.2). Eighty-five patients (91%) received at least one further active treatment for mCRPC with outcomes below. Conclusion(s): Abiraterone, enzalutamide, and cabazitaxel all demonstrate activity for 1L mCRPC following progression on D-ADT. Compared to historical controls, PSA responses appear less than pre-docetaxel, but greater than the post-docetaxel setting.

Background: Trials of lutetium prostate specific membrane antigen (PSMA) in men with metastatic castration-resistant prostate cancer (mCRPC) have demonstrated good safety and efficacy, but combination strategies may improve outcomes. Idronoxil is a synthetic flavonoid derivative with radiosensitising properties. Objective(s): To evaluate the safety and activity of 177Lu PSMA 617 (LuPSMA-617) in combination with idronoxil suppositories (NOX66) in patients with end-stage mCRPC. Design, setting, and participants: Thirty-two men with progressive mCRPC previously treated with taxane-based chemotherapy (91% treated with both docetaxel and cabazitaxel) and abiraterone and/or enzalutamide were enrolled in this phase I dose escalation study with phase II dose expansion. Intervention(s): Screening with 68Ga PSMA and 18F-fludeoxyglucose positron emission tomography (PET)/computed tomography (CT) was performed. Men received up to six cycles of LuPSMA-617 (7.5 GBq) on day 1, with escalating doses of NOX66 on days 1-10 of a 6-wk cycle. Cohort 1 (n = 8) received 400 mg and cohort 2 (n = 24) 800 mg of NOX66. Outcome measurements and statistical analysis: Adverse events (AEs), pain inventory scores, prostate-specific antigen (PSA) response, progression-free survival, and overall survival were evaluated. Results and limitations: Fifty-six men were screened and 32 (57%) were enrolled with a screen failure rate of 21% for PET imaging criteria. Dosing was as follows: 97% (31/32) received two or more doses and 47% (15/32) completed six doses. Common AEs included xerostomia, fatigue, and anaemia. Anal irritation attributable to NOX66 occurred in 28%. PSA responses were as follows: 91% (29/32) had any PSA response (median -74%; 95% confidence interval [CI] 76-97) and 62.5% (20/32) had a PSA fall of >50% (95% CI 45-77). The median PSA progression-free survival was 6.1 mo (95% CI 2.8-9.2) and median overall survival was 17.1 mo (95% CI 6.5-27.1). Conclusion(s): NOX66 with LuPSMA-617 is a saf

Background: Recent trials randomising patients (pts) receiving systemic cancer therapy showed that prophylactic anticoagulation (PAK) halves the risk of venous thromboembolic events (VTE) and doubles the risk of bleeding (Khorana et al. & Carrier et al., both NEJM 2019). In pts with metastatic germ cell tumors (mGCT) VTE is a frequent complication but it remains unclear whether PAK should be recommended because the number of mGCT pts in those trials was small. We aimed to determine the risk of VTE before, during and after chemotherapy and in mGCT pts without and with risk factors for VTE (retroperitoneal lymph nodes, Khorana score, venous access device) and to calculate the number needed to treat (NNT) and number needed to harm (NNH) of PAK. Method(s): This retrospective analysis included mGCT pts treated with first-line platinum-based chemotherapy. We excluded patients who received PAK, with a known history of coagulopathy or VTE and extracted data about VTE and bleeding events. Cumulative VTE incidence was calculate for patients without and with increasing number of known risk factors for VTEs. NNT and NNH were calculated by assuming similar hazard ratios (HR) to reduce VTEs and increase bleeding as previously published (HR 0.66 and 1.96, Khorana et al., NEJM 2019). Result(s): Out of 1039 pts, 132 (13%) presented with VTE, 6 (1%) with bleeding. One patients died of VTE and 1 because of bleeding. Patients without any VTE risk factors experience VTE in 20/347 (5%) which translated into a NNT of 55 compared to the NNH of 84 respectively. Before start of chemotherapy 52 (5%) pts (NNT=60) presented with VTE of which 22 were reported symptomatic 21 asymptomatic/incidentally detected VTE on staging scans (9 unknowns). During chemotherapy 79 (8%) pts (NNT=40) were diagnosed with VTE whereas 19 (2%) pts (NNT=162) were diagnosed with VTE after chemotherapy. Conclusion(s): Our analysis revealed that even mGCT patients without risk factors for VTE show a relevant cumulative V

Background: The expression of androgen receptor splice variants (AR-V) in mCRPC patients has widely been regarded as a predictive biomarker for non-response to AR-targeted therapies. However, recent data from our group and others has questioned this association. We report new data from our whole blood assay, correlating baseline and end-of-treatment (EOT) AR-V7 and AR-V9 expression with clinical outcomes in mCRPC patients treated with abiraterone or enzalutamide. Method(s): We have previously developed a whole-blood, quantitative polymerase chain reaction assay for detecting circulating AR-V7 and AR-V9. The assay was applied to samples prospectively collected from 48 mCRPC patients immediately prior to commencing abiraterone or enzalutamide, and where available, at treatment cessation. Patients positive for either AR-V7 or AR-V9 were defined as AR-V-positive, and AR-Vnegative if neither variant was detected. All AR-V-positive samples underwent confirmatory DNA sequencing to confirm variant expression. AR-V expression was correlated with PSA response rate (chi-square test) and PSA progression-free survival (PSA-PFS) (logrank test). Result(s): The median follow-up was 10.6 mo. Twelve out of 48 patients (25%) were AR-V-positive, with no samples positive for both variants at baseline. Similar response rates were observed in AR-V-positive (7/12) and AR-V-negative (23/36) patients (50% vs. 64%, p = 0.7). PSA-PFS did not differ significantly between groups (8.1 mo vs. not reached, p = 0.5). EOT samples were available in nine patients, with four exhibiting AR-V-positivity. Of these, two (50%) patients were AR-V-positive at baseline, and two (50%) patients converted from AR-V-negative to AR-V-positive at treatment cessation (PSA-PFS 3.4 and 2.6 mo respectively). One of the conversion patients transitioned from V7-/V9- to V7+/V9+. Neither AR-V7 nor AR-V9 were detected in any of 13 normal male controls. Conclusion(s): With extended follow-up, whole blood expression of AR-V7 an

Background: Identifying predictive biomarkers for mCRPC patients receiving androgen receptor signalling inhibitors (ARSI) or chemotherapy remains an unmet clinical need. FOLH1 encodes for ProstateSpecific Membrane Antigen (PSMA), a type II glycoprotein highly expressed on prostate cancer cells. We designed a whole blood assay to detect FOLH1 mRNA, and correlated expression with clinical outcomes in patients commencing ARSI (abiraterone or enzalutamide) or chemotherapy (docetaxel or cabazitaxel). Method(s): mCRPC patients commencing ARSI or chemotherapy were prospectively recruited at three Australian centres from June 2016 to July 2018. A quantitative reverse transcription polymerase chain reaction assay was used to detect FOLH1 transcript from whole blood samples collected in PAXgene RNA tubes. Pre-treatment FOLH1 expression was correlated with PSA response rate (Fisher's exact test) and PSA progression-free survival (PSA-PFS) (log-rank test). Result(s): Median follow-up was 13.6 months (IQR 9.7-19.3). In total, 88 pretreatment samples were analysed, of which 75 (85%) were FOLH1-positive. In patients receiving ARSI, outcomes favoured FOLH1-positive patients compared to FOLH1negative patients, with higher PSA response rates (39/60, 65% vs. 2/7, 29%; p = 0.1) and longer PSA-PFS (median 9.0 months [95% CI, 7.210.8] vs. 2.8 months [95% CI, 2.33.3] ; p = 0.03). Conversely, in chemotherapy-treated patients, inferior outcomes were observed in FOLH1-positive patients compared to FOLH1negative patients, with lower PSA response rates (4/15, 27% vs. 5/6, 83%, p = 0.05) and shorter PSA-PFS (median 2.9 months [95% CI, 2.83.0] vs. 4.1 months [95% CI, 3.74.5] ; p = 0.32). Conclusion(s): Pre-treatment FOLH1 expression may differentiate between outcomes on ARSI vs. chemotherapy in mCRPC patients. The utility of FOLH1 as a predictive biomarker in mCRPC warrants further evaluation in larger, independent cohorts. (Table Presented) .

Objective: Identifying predictive and/or prognostic biomarkers in the context of an ever-expanding therapeutic armamentarium for metastatic castrate-resistant prostate cancer (mCRPC) patients remains an unmet clinical need. Our objective was to develop a prognostic whole blood gene signature for mCRPC patients commencing systemic therapy. Method(s): We obtained pre-treatment whole blood samples in PAXgene RNA tubes from 115 mCRPC patients commencing androgen receptor (AR) pathway inhibitors (n = 81) or chemotherapy (n = 34) across threeAustralian centres from June 2016 to July 2018. The presence of 10 prostate cancer-associated transcripts was assessed using reverse transcription polymerase chain reaction (RT-PCR). Gene transcripts correlating with overall survival (OS) at P < .10 in univariate Cox regression models were incorporated into a multigene signature, before assessing for association with clinical outcomes. The prognostic strength of the signature was further evaluated using a concordance probability estimate (CPE). Result(s): A total of four genes were incorporated into a multigene signature: AR splice variant 7 (AR-V7), and three androgen-regulated genes: GRHL2, HOXB13 and FOXA1. Increasing number of positive transcripts stratified for survival outcomes (median OS: not reached vs 24.8 months vs 16.2 months for 0, 1 and >=2 transcripts, respectively; P = .0052). Strikingly, thismultigene signature retained prognostic significance on multivariable analysis (HR 2.1, 95% CI 1.1-4.0, P = .019). The CPE for this model was 0.78, indicating that the signature was a strong discriminator of patient prognosis. Conclusion(s): In this prospective, multicentre study, a novel whole blood AR-based multigene signature demonstrated strong prognostic utility in a cohort of mCRPC patients commencing contemporaneous systemic therapies. This signature may play a valuable role in upfront risk stratification of mCRPC patients, which in turn may inform on design of future clinic

Background: The field of liquid biopsies in oncology is rapidly expanding, with the application of cell-free circulating tumour DNA (ctDNA) showing promise in this era of precision medicine. Compared with traditional clinical and radiographic tumour monitoring methods, the analysis of ctDNA provides a minimally-invasive and technically feasible approach to assess temporal and spatial molecular evolutions of the tumour landscape. The constantly advancing technological platforms available for ctDNA extraction and analysis allow greater analytical sensitivities than ever before. The potential translational impact of ctDNA as a blood-based biomarker for the identification, characterization and monitoring of cancer has been demonstrated in numerous proof-of-concept studies, with ctDNA analysis beginning to be applied clinically across multiple facets of oncology. Conclusion(s): In this review we discuss the biology, recent advancements, technical considerations and clinical implications of ctDNA in the context of cancer, and highlight important challenges and future directions for the integration of ctDNA into standardised patient care.Copyright © 2018, International Society for Cellular Oncology.

Background: Plasma circulating tumour DNA (ctDNA) in prostate cancer has emerged as a promising minimally invasive tool with which to interrogate the cancer genome. However, detection of copy number variations (CNVs) in ctDNA has proved challenging, which poses a major problem in mCRPC, which commonly harbours pathogenic CNVs. Here, we use an ultra-sensitive next-generation sequencing (NGS) assay to identify CNVs in ctDNA from mCRPC patients and correlate findings with clinical outcomes in men commencing androgen receptor pathway inhibitors (ARPIs) or chemotherapy. Method(s): Plasma from mCRPC patients commencing therapy was collected and platelet poor plasma (PPP) fractions were processed uniformly and cell-free DNA (cfDNA) extracted. Plasma samples were analysed using the PredicineLITE NGS assay, which reports genomic alterations in 90 cancer genes. CNVs from this cohort were correlated with PSA response rate (Fisher's exact test), PSA progression-free survival (PSA-PFS), clinical/radiographic progression-free survival (clinical/ rPFS) and overall survival (OS). Result(s): Median follow-up was 19.85 months (mo) (IQR 12.5-23.0). In total, 32 pre-treatment samples were analysed (7 chemotherapy, 25 ARPI). The most common CNVs were PTEN loss (n = 12, 38% of cohort), RB1 loss (n = 5, 16%) and AR gain (n = 12, 38%). Notably, OS was decreased in patients with PTEN loss (median 9.7mo vs. not reached; P=.03) andRB1 loss (median 7.1movs. 17.1 mo; P=.1), while 48 POSTER ABSTRACTS PSA response rates were also lower in RB1 loss (1/5, 20% vs 19/27, 71%; P = .053). In addition, AR copy number gain was associated with decreased clinical/rPFS (median 3.4 mo vs 10.7 mo; P = .05) and inferior OS (median 9.7 mo vs not reached; P = .05). Conclusion(s): Using an ultra-sensitive NGS assay, we demonstrate the robust detection of CNVs in plasma ctDNA of patients with mCRPC. Copy number losses of PTEN and RB1, and gains ofARwere associated with worse clinical outcomes on chemotherapy and A

Background: Due to difficulties with routine metastatic tissue biopsy in mCRPC, the identification of prognostic and predictive biomarkers for treatment with androgen-receptor signalling inhibitors (ARSI) and chemotherapy remains an unmet clinical need. Plasma circulating tumor DNA (ctDNA) has emerged as a promising minimally-invasive tool with which to interrogate the cancer genome. However, detection of copy number variations (CNVs) in ctDNA has proved challenging. This poses a major problem in mCRPC, which commonly harbours pathogenic CNVs. Here we use an ultra-sensitive next-generation sequencing (NGS) assay to identify CNVs in ctDNA from mCRPC patients and correlate findings with clinical outcomes in men commencing ARSI (abiraterone or enzalutamide) or chemotherapy (docetaxel or cabazitaxel). Method(s): MCRPC patients commencing ARSI or chemotherapy were prospectively recruited at two Australian centers. Plasma was collected and platelet poor plasma (PPP) fractions were processed uniformly and cell-free DNA (cfDNA) extracted. Plasma samples were analysed using the PredicineLITE NGS assay, which reports genomic alterations in 90 cancer genes. CNVs from this cohort were correlated with PSA response rate (Fisher's exact test), PSA progression-free survival (PSA-PFS), clinical/radiographic progression-free survival (clinical/rPFS), and overall survival (OS). Result(s): Median follow-up was 19.85 months (mo) (IQR 12.5-23.0). In total, 32 pre-treatment samples were analyzed (7 chemotherapy, 25 ARSI). The most common CNVs were PTEN loss (n=12, 38% of cohort), RB1 loss (n=5, 16%) and AR gain (n=12, 38%). Notably, OS was decreased in patients with PTEN loss (median 9.7 mo vs. not reached; p=0.03) and RB1 loss (median 7.1 mo vs. 17.1 mo; p=0.1), while PSA response rates were also lower in RB1 loss (1/5, 20% vs. 19/27, 71%; p=0.053). In addition, AR copy number gain was associated with decreased clinical/rPFS (median 3.4 mo vs. 10.7 mo; p=0.05) and inferior OS (median 9.7

Aim: Targeted therapy (TT) has improved survival for metastatic renal cell carcinoma (mRCC). However, survival is usually limited if brain metastases (BMs) develop. We aimed to evaluate survival outcomes in mRCC patients based on timing of BM diagnosis. Method(s): We conducted a multicenter, retrospective study of mRCC patients with BM who received TT at any point between 2005 and 2014. We determined overall survival (OS) from stage IV diagnosis, TT initiation and BM diagnosis, and prognostic factors. Patients were grouped into three categories: synchronous-BM, metachronous-BM diagnosed while conservatively managed (metachronous-BM before TT) and metachronous-BM diagnosed during TT. Survival was calculated by Kaplan-Meier method and predictors were calculated using Cox hazards regression. Result(s): Incidence of BM was 17% in mRCC patients treated with TT (two centers). Fifty-four mRCC-BM patients were identified from five tertiary centers. Twenty-eight percentage (15/54) had synchronous-BM, 28% (15/54) had metachranous-BM before TT and 44% (24/54) had metachronous-BM during TT. Most had central nervous system (CNS) symptoms at BM diagnosis (78%; 42/54). Median OS from stage IV diagnosis, TT commencement and BM diagnosis was 28 months (95% confidence interval [CI] 16-43), 19 months (95% CI 9-26) and 9 months (95% CI 5-16), respectively. Synchronous-BM group trended toward poorer survival from TT commencement (P = 0.06). Metachronous-BM during TT group had lower survival from BM diagnosis than synchronous-BM and metachronous-BM before TT group (P < 0.001). Eight of 50 deaths (16%) were from neurological complications. The presence of CNS symptoms did not predict worse survival from stage IV diagnosis (P = 0.73). Conclusion(s): In patients with mRCC, the development of BM while on TT portends shorter prognosis compared with synchronous diagnosis of BM at stage IV disease or metachronous BM developed prior to commencing TT. The presence of CNS symptoms does not predict

Background: The treatment paradigm for metastatic castration-resistant prostate cancer (mCRPC) has evolved significantly in recent years. Identifying predictive and/or prognostic biomarkers in the context of this rapidly expanding therapeutic armamentarium remains a pressing and unmet clinical need. Objective(s): To develop a prognostic whole-blood gene signature for mCRPC patients. Design, setting, and participants: As part of an ongoing prospective, multicentre biomarker research study (Australian Prostate Biomarker Alliance), we enrolled 115 mCRPC patients commencing chemotherapy (n = 34) or androgen receptor (AR) pathway inhibitors therapy (n = 81) and obtained pretreatment whole-blood samples in PAXgene RNA tubes. Gene expression was assessed using reverse transcription-polymerase chain reaction. Outcome measurements and statistical analysis: Gene transcripts correlating with overall survival (OS) at p < 0.10 in univariate Cox regression models were incorporated into a multigene signature. Kaplan-Meier survival estimates and multivariate analyses were used to assess association with clinical outcomes. Prognostic strength of the signature was estimated using a concordance probability estimate (CPE). Results and limitations: Based on univariate analysis for OS, the following genes were incorporated into a multigene signature: AR splice variant 7 (AR-V7), and three androgen-regulated genes: GRHL2, HOXB13, and FOXA1. The number of positive transcripts clearly stratified survival outcomes (median OS: not reached vs 24.8 mo vs 16.2 mo for 0, 1, and >=2 transcripts, respectively; p = 0.0052). Notably, this multigene signature retained prognostic significance on multivariable analysis (hazard ratio, 2.1; 95% confidence interval, 1.1-4.0; p = 0.019). Moreover, CPE for this model was 0.78, indicating strong discriminative capacity. Limitations include short follow-up time. Conclusion(s): Our data demonstrate the prognostic utility of a novel whole-blood AR-based signatur, We demonstrated that a whole-blood androgen receptor-based multigene signature was an important prognostic tool in a cohort of metastatic castration-resistant prostate cancer (mCRPC)patients receiving contemporaneous systemic treatment. This signature may have a valuable role in upfront risk stratification and prognostication of mCRPC patients. Background: The treatment paradigm for metastatic castration-resistant prostate cancer (mCRPC)has evolved significantly in recent years. Identifying predictive and/or prognostic biomarkers in the context of this rapidly expanding therapeutic armamentarium remains a pressing and unmet clinical need. Objective(s): To develop a prognostic whole-blood gene signature for mCRPC patients. Design, setting, and participants: As part of an ongoing prospective, multicentre biomarker research study (Australian Prostate Biomarker Alliance), we enrolled 115 mCRPC patients commencing chemotherapy (n = 34)or androgen receptor (AR)pathway inhibitors therapy (n = 81)and obtained pretreatment whole-blood samples in PAXgene RNA tubes. Gene expression was assessed using reverse transcription-polymerase chain reaction. Outcome measurements and statistical analysis: Gene transcripts correlating with overall survival (OS)at p < 0.10 in univariate Cox regression models were incorporated into a multigene signature. Kaplan-Meier survival estimates and multivariate analyses were used to assess association with clinical outcomes. Prognostic strength of the signature was estimated using a concordance probability estimate (CPE). Results and limitations: Based on univariate analysis for OS, the following genes were incorporated into a multigene signature: AR splice variant 7 (AR-V7), and three androgen-regulated genes: GRHL2, HOXB13, and FOXA1. The number of positive transcripts clearly stratified survival outcomes (median OS: not reached vs 24.8 mo vs 16.2 mo for 0, 1, and >=2 transcripts, respectively; p = 0.0052). Notably, this multigene signature retain