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Radiotherapy plays an essential role in the treatment of more than half of all patients with cancer. In recent decades, advances in devices that deliver radiation and the development of treatment planning software have helped radiotherapy attain precise tumour targeting with minimal toxicity to surrounding tissues. Simultaneously, as more targeted drug therapies are being brought into the market, there has been significant interest in improving cure rates for cancer by adding drugs to radiotherapy to widen the therapeutic window, the difference between normal tissue toxicity and treatment efficacy. The development of new combination therapies will require judicious adaptation of preclinical models that are routinely used for traditional drug discovery. Here we highlight the strengths and weaknesses of each of these preclinical models and discuss how they can be used optimally to identify new and clinically beneficial drug–radiotherapy combinations.

PURPOSE Adjuvant compared with early salvage radiation therapy (sRT) following radical prostatectomy (RP) has not been shown to reduce progression-free survival in randomized controlled trials. However, these trials might have missed a benefit in men with adverse pathology at RP given that these men were under-represented and immortal time bias might have been present; herein, we investigate this possibility. METHODS We evaluated the impact of adjuvant versus early sRT on all-cause mortality (ACM) risk in men with adverse pathology defined as positive pelvic lymph nodes (pN1) or pGleason score 8-10 prostate cancer (PC) and disease extending beyond the prostate (pT3/4). We used a treatment propensity score to minimize potential treatment selection bias when estimating the causal effect of adjuvant versus early sRT on ACM risk and a sensitivity analysis to assess the impact that varying definitions of adverse pathology had on ACM risk adjusting for age at RP, PC prognostic factors, site, and the time-dependent use of post-RP androgen deprivation therapy. RESULTS After a median follow-up (interquartile range) of 8.16 (6.00-12.10) years, of the 26,118 men in the study cohort, 2,104 (8.06%) died, of which 539 (25.62%) were from PC. After excluding men with a persistent prostate-specific antigen, adjuvant compared with early sRT was associated with a significantly lower ACM risk among men with adverse pathology at RP when men with pN1 PC were excluded (0.33 [0.13-0.85]; P = .02) or included (0.66 [0.44-0.99]; P = .04). CONCLUSION Adjuvant radiation therapy should be considered in men with pN1 or pGleason score 8 to 10 and pT3/4 PC given the possibility that a significant reduction in ACM risk exists.

Androgen deprivation therapy (ADT) is not recommended for low-risk prostate cancer because of its lack of benefit and potential for harm. We evaluated the incidence and predictors of ADT use in low-risk disease.Using the National Cancer Database, we identified 197,957 patients with low-risk prostate cancer (Gleason score of 3 + 3 = 6, prostate-specific antigen level10 ng/mL, and cT1-T2a) diagnosed from 2004 to 2012 with complete demographic and treatment information. We used multiple logistic regression to evaluate predictors of ADT use and Cox regression to examine its association with all-cause mortality.Overall ADT use decreased from 17.6% in 2004 to 3.5% in 2012. In 2012, 11.5% of low-risk brachytherapy patients and 7.6% of external beam radiation therapy patients received ADT. Among 82,352 irradiation-managed patients, predictors of ADT use included treatment in a community versus academic cancer program (adjusted odds ratio [AOR], 1.60; 95% confidence interval [CI], 1.50-1.71; P.001; incidence, 14.0% vs 6.0% in 2012); treatment in the South (AOR, 1.51), Midwest (AOR, 1.81), or Northeast (AOR, 1.90) versus West (P.001); and brachytherapy use versus external beam radiation therapy (AOR, 1.32; 95% CI, 1.27-1.37; P.001). Among 25,196 patients who did not receive local therapy, predictors of primary ADT use included a Charlson-Deyo comorbidity score of ≥2 versus 0 (AOR, 1.42; 95% CI, 1.06-1.91; P=.018); treatment in a community versus academic cancer program (AOR, 1.61; 95% CI, 1.37-1.90; P.001); and treatment in the South (AOR, 1.26), Midwest (AOR, 1.52), or Northeast (AOR, 1.28) versus West (P≤.008). Primary ADT use was associated with increased all-cause mortality in patients who did not receive local therapy (adjusted hazard ratio, 1.28; 95% CI, 1.14-1.43; P.001) after adjustment for age and comorbidity.ADT use in low-risk prostate cancer has declined nationally but may remain an issue of concern in certain populations and regions.

Purpose It is clinically challenging to integrate genomic-classifier results that report a numeric risk of recurrence into treatment recommendations for localized prostate cancer, which are founded in the framework of risk groups. We aimed to develop a novel clinical-genomic risk grouping system that can readily be incorporated into treatment guidelines for localized prostate cancer. Materials and Methods Two multicenter cohorts (n = 991) were used for training and validation of the clinical-genomic risk groups, and two additional cohorts (n = 5,937) were used for reclassification analyses. Competing risks analysis was used to estimate the risk of distant metastasis. Time-dependent c-indices were constructed to compare clinicopathologic risk models with the clinical-genomic risk groups. Results With a median follow-up of 8 years for patients in the training cohort, 10-year distant metastasis rates for National Comprehensive Cancer Network (NCCN) low, favorable-intermediate, unfavorable-intermediate, and high-risk were 7.3%, 9.2%, 38.0%, and 39.5%, respectively. In contrast, the three-tier clinical-genomic risk groups had 10-year distant metastasis rates of 3.5%, 29.4%, and 54.6%, for low-, intermediate-, and high-risk, respectively, which were consistent in the validation cohort (0%, 25.9%, and 55.2%, respectively). C-indices for the clinical-genomic risk grouping system (0.84; 95% CI, 0.61 to 0.93) were improved over NCCN (0.73; 95% CI, 0.60 to 0.86) and Cancer of the Prostate Risk Assessment (0.74; 95% CI, 0.65 to 0.84), and 30% of patients using NCCN low/intermediate/high would be reclassified by the new three-tier system and 67% of patients would be reclassified from NCCN six-tier (very-low– to very-high–risk) by the new six-tier system. Conclusion A commercially available genomic classifier in combination with standard clinicopathologic variables can generate a simple-to-use clinical-genomic risk grouping that more accurately identifies patients at low, intermediate, and high risk for metastasis and can be easily incorporated into current guidelines to better risk-stratify patients.

Aims Trastuzumab, in combination with chemotherapy, is the standard of care for patients with early and metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer. The Retreatment after HErceptin Adjuvant trial assessed the efficacy and safety of trastuzumab plus a taxane as first-line treatment for patients with metastatic breast cancer (MBC) who had relapsed after adjuvant trastuzumab for HER2-positive early breast cancer. Materials and methods In total, 43 patients with HER2-positive MBC who had received previous adjuvant trastuzumab for ≥10 months, with a relapse-free interval of ≥6 months after the last adjuvant trastuzumab dose, were recruited. Eligible patients ( n = 41) were assigned to receive trastuzumab, either weekly or every 3 weeks, in combination with docetaxel or paclitaxel until disease progression. Results At the final analysis, with a median follow-up time of 40 months, a positive response was observed in 25/41 patients (61%; 95% confidence interval: 48.7–80.4%), stable disease in 7/41 (17.1%) and progressive disease in 6/41 (14.6%). Three patients had missing response assessments (one had no measurable lesions at baseline and two had no post-baseline tumour assessments). The median progression-free survival (PFS) was 8.0 months (95% confidence interval: 6–11 months) and the median overall survival was 25.0 months (16–33 months). No correlation was found between response rate, PFS or overall survival and the duration of adjuvant trastuzumab treatment, trastuzumab-free interval, relapse-free interval, hormone receptor status or type of pre-metastatic treatment. The most common adverse events (all grades) were alopecia (32%) and diarrhoea (32%). Six patients (14.6%) developed at least one serious adverse event. No congestive heart failure or any unexpected adverse events were reported. Conclusion Trastuzumab, in combination with a taxane, is an effective and well-tolerated first-line treatment for MBC in patients who relapse after trastuzumab-based adjuvant therapy.

PURPOSE/OBJECTIVE(S) Prognostic factors that alter prostate cancer effect include TNM stage, pre-treatment PSA, Gleason score, and Gleason grade group (2). Of these, Gleason score yields the largest impact on cause-specific survival (CSS) (5). While Gleason score is crucial to predicting outcomes, disparity between biopsy and prostatectomy sample scores is often seen. This can result in Gleason score upgrading (GSU) and downgrading (GSD) at the time of surgery. Phillips et al. explored this phenomenon through combining the lowest and highest Gleason scores at biopsy (ComboGS) and examining how such a factor would impact GSU and prostate cancer specific survival (PCSM). This study aims to validate the Phillips et al. findings via an independent cohort of prostate cancer patients treated with definitive dose-escalated radiation therapy (DE-RT) at a single institution. MATERIALS/METHODS DE-RT was administered to 2,539 men; 687 men had a ComboGS. We utilized univariate and multivariable analysis to evaluate relapse rates and clinical outcomes. To further ascertain the ComboGS prognostic impact, we employed the Cancer of the Prostate Risk Assessment Score (CAPRA) and the modified CAPRA (mCAPRA). Rates of biochemical event-free survival (bEFS) and distant metastasis-free survival (DMFS) were compared across CAPRA scores, with and without modification, and the prognostic value of the CAPRA scores were compared using Harrel's concordance index (C-index) (12). RESULTS ComboGS presence in Gleason 7-10 prostate cancer patients generated improved 10-year biochemical event-free survival (bEFS) from 76.6% to 82.4% (HR 0.75, CI 0.59-0.96, P = 0.021), 10-year distant metastasis-free survival (DMFS) from 89.3% to 93.2% (HR 0.57, CI 0.39-0.85, P = 0.005), 10-year PCSM from 93.9% to 97.4% (HR 0.39, CI 0.21-0.7, P = 0.001) and 10-year overall survival (OS) from 65.7% to 75.6% (HR 0.69, CI 0.57-0.83, P < 0.001). Multivariable analysis also supported that ComboGS is protective for biochemical failure (HR 0.64, CI 0.50-0.83, P < 0.001), distant metastasis (HR 0.42, CI 0.28-0.63, P < 0.001), death from prostate cancer (HR 0.32, CI 0.17-0.58, P < 0.001), and overall mortality (HR 0.65, CI 0.54-0.79, P < 0.001). Additionally, adjusting the CAPRA score for ComboGS decreased the risk of biochemical failure (BF) by nearly 30% (HR = 0.70 [95% CI, 0.55-0.88], P = 0.003) and by 50% (HR = 0.54 [95% CI, 0.37-0.80], P = 0.002) for distant metastasis. CONCLUSION ComboGS is a useful and readily available independent prognostic factor for all clinical endpoints (biochemical failure, distant metastasis, cancer-specific survival and overall survival). Moreover, the ComboGS can be used in conjunction with the extensively validated CAPRA scoring, to better risk stratify patients being treated with definitive DE-RT and possibly de-escalate therapy for some men with ComboGS 7 disease.

575 Background: Trastuzumab (H) is the standard of care for patients with early and advanced HER2-positive breast cancer. It is therefore important to investigate the benefit of retreatment with H ...

4585 Background: Prostate cancer (PCa) recurrence can be identified by biochemcial failure (BF) many years prior to clinical recurrence. A short IBF (

35 Background: The percent of positive biopsy cores (PPC)-considered a surrogate of local disease burden-has been shown to predict biochemical failure (BF) after external beam radiation therapy (EBRT), but most series have used conventional dose RT. Dose-escalated RT has been demonstrated to improve prostate cancer outcomes, but the value of PPC is unclear in the setting of RT doses high enough to decrease local failure. Methods: A retrospective evaluation was performed of 651 patients treated to ≥75 Gy with biopsy core information available. Patients were stratified for PPC by quartile, and differences by quartile in BF, freedom from metastasis (FFM), cause specific survival (CSS), and overall survival (OS) were assessed using the log-rank test. Receiver operated characteristic (ROC) curve analysis was utilized to determine an optimal cut-point for PPC. Cox proportional hazards multivariate regression was utilized to assess the impact of PPC on clinical outcome when adjusting for risk group. Results: With median follow-up of 62 months the median number of cores sampled was 7 (IQR: 6–12) with median PPC in 38% (IQR: 17%-67%). On log-rank test, BF, FFM, and CSS were all associated with PPC (p < 0.005 for all), with worse outcomes only for the highest PPC quartile (>67%). There was no observed difference in OS based upon PPC. ROC curve analysis confirmed a cut-point of 67% as most closely associated with CSS (p67% increased the risk for BF (p Conclusions: For patients treated with dose-escalated RT, the PPC adds prognostic value but at a higher cut-point then previously utilized. Patients with PPC >67% remain at increased risk for failure even with dose-escalated EBRT and may receive benefit from further intensification of therapy. No significant financial relationships to disclose.

15 Background: The division of Gleason score (GS) into three categories (2-6, 7, 8-10), may not fully utilize its prognostic power as shown by recent reports demonstrating that the presence of Gleason Pattern 5 (GP5) is a strong adverse prognostic factor. Therefore, we analyzed clinical outcomes for patients treated with dose-escalated radiation therapy (RT) based upon the presence or absence of GP5 within the biopsy specimens. Methods: Clinical outcomes were analyzed for 718 men treated for localized prostate cancer with definitive external beam RT to at least 75 Gy. We assessed the impact of GP5 as well as pre-treatment and treatment related factors on freedom from biochemical failure (FFBF), freedom from metastasis (FFM), cause-specific survival (CSS), and overall survival (OS). Results: Median follow-up was 64 months. At biopsy, 89% of patients had no GP5 while 11% had GP5. There was no difference in age, co-morbid illness, clinical T-stage, PSA, or the use or duration of androgen deprivation therapy (ADT) between GS8 without GP5 and GS8-10 with GP5. The presence of GP5 predicted lower FFM (p Conclusions: The presence of GP5 predicts for worse clinical behavior, which therefore needs to be accounted for by risk stratification schemes. Further intensification of local and/or systemic therapy may be appropriate for such patients. No significant financial relationships to disclose.