Feng, Felix Y.

ABSTRACTBackgroundWe aim to evaluate whether increased lymph node yield at prostatectomy (RP) is associated with improved outcomes in NRG/RTOG 9601, a randomized clinical trial of men who underwent either radiation (RT) alone or RT + bicalutamide for PSA elevation following RP for pT2/T3 prostate cancer.MethodsWe reviewed available pathology reports for patients in NRG/RTOG 9601 to determine the nodal count at RP. Cox proportional hazards models were used to assess effect of lymph nodes yield, arm (RT alone or RT + bicalutamide), Gleason score, positive margins, and seminal vesicle invasion on the following endpoints: times to local and distant failure and overall and disease‐specific survival.ResultsOf 760 patients, 552 (73%, 276 in each arm) had complete data available. Median node count in the entire cohort was 6 (range: 0–33, IQR: 3–9). There were no significant differences between arms in terms of patient demographic or clinical characteristics, including total lymph nodes removed in either arm. There was no significant association between total lymph nodes and overall or disease‐specific survival with both arms combined and when adjusting for arm. Notably, interaction analysis revealed that in seminal vesicle invasion, there was a significant association between lymph node yield and OS and DSS (HR = 0.91, 95% CI: 0.83–0.99, p = 0.034; HR = 0.87, 95% CI: 0.77–0.99, p = 0.029, respectively).ConclusionsAlthough lymph node yield in NRG/RTOG 9601 did not show association with adverse outcomes in the entire cohort or either arm alone, there was significant association between lymph node yield and adverse outcomes when seminal vesicle invasion was present. The therapeutic benefit of extensive lymph node dissection remains uncertain but could be more relevant in higher risk patients.

387 Background: Level 1 evidence supports treatment of high-risk and node positive PCa using 4-9 weeks of radiotherapy (RT) combined with 18-36 months of androgen deprivation therapy (ADT) with or without abiraterone acetate plus prednisone (AAP). While effective, some cancers recur, and this prolonged treatment is associated with inconvenience and variable morbidity. We aimed to determine whether the biological synergy of stereotactic body radiotherapy (SBRT) with a 6-month combination of ADT, AAP, and the PARP inhibitor niraparib, could enable a shorter intensified, yet safe and effective, therapeutic alternative. Methods: ASCLEPIuS (NCT04194554) is a multicenter investigator-initiated phase I/II trial in high-risk or node positive, homologous recombination unselected, PCa. Patients received 6 months of ADT, AAP, niraparib and SBRT to the prostate (37.5-40 Gy) +/- pelvic lymph nodes (25 Gy). Focal prostate/nodal boosting was permitted. The phase I primary endpoint was the maximum tolerated dose (MTD) of niraparib using the time-to-event continuous reassessment method (3 dose levels: 100 mg and 200 mg held during SBRT, or 200 mg concurrent with SBRT). Dose limiting toxicities (DLT) were any persistent grade 4+ hematologic toxicity or any grade 3+ rectal/urinary toxicity at least possibly related to treatment as assessed by CTCAE v5.0. Patient reported quality of life (QOL) was assessed with the EPIC-26 short form. Linear mixed models were used to compare scores over time. Results: Accrual began in Nov. 2020 with a transition from phase I to phase II in May 2023 after enrolling 54 men. Median follow-up of the phase I cohort is 12.1 months (IQR 9.4-18.9), 80% (n=43) had Grade Group 4-5, median PSA was 17 ng/mL (range, 1-73), 15% (n=8) had cN+ disease, and 76% (n=41) received nodal RT. There were 0 DLTs to date, no grade 3+ rectal or urinary toxicities, and 5 serious adverse events at least possibly attributable to study treatment (anemia, non-rectal gastrointestinal, syncope, infection, musculoskeletal). The most common grade 3 toxicities were hypertension (n = 11, 21%) and leukopenia (n=6, 11%). Transient dose reductions or holds of AAP or niraparib occurred in 10 and 11 patients, respectively. There were no statistically significant declines in patient reported urinary QOL at 6- or 12-months post-treatment compared to baseline (all p >0.15). A transient decline in bowel QOL at 6-months occurred (p<0.01), which improved by 12-months (p=0.16). Conclusions: Our phase I findings support the short-term safety and tolerability of the combination of SBRT to the prostate and nodes, ADT, AAP, and niraparib at an MTD of 200 mg in men with high-risk or node positive PCa. Our trial completed phase II enrollment in May 2024, and longer-term safety, efficacy, and genomic correlations will be presented in the future. Clinical trial information: NCT04194554 .

3 Background: Previous reports suggested that AAT when combined with salvage RT following RP in patients may improve prostate cancer control outcomes. Methods: Post-RP patients with pT3pN0 or with pT2pN0 and positive margins who had or developed elevated PSA levels from 0.2 to 4.0 ng/ml were randomized on a phase III, double-blind, trial of RT + placebo (64.8 Gy in 36 fractions of 1.8 Gy) vs. RT + AAT (24 months bicalutamide, 150 mg daily) during and after RT. The primary end-point was overall survival. Trial design required 725 patients and provided 80% power to detect a reduction in death rate by at least 28.5% and a 1-sided significance level of 0.046. Results: From 3/98 to 3/03, 761 eligible patients (median age 65) were randomized to RT + AAT (384) or RT + placebo (377). 248 patients (33%) were pT2pN0 and 513 (67%) were pT3pN0. 671 (88%) had a PSA nadir after RP of < 0.5 ng/ml. 649 (85%) had an entry PSA value of <1.6, 112 patients (15%) had an entry PSA of 1.6-4. Median follow up was 12.6 years. Actuarial overall survival at 10 years was 82% for RT plus AAT and 78% for RT + placebo and a hazard ratio of 0.75 (95% CI: 0.58-0.98) with a 1-sided p value of 0.018 (2-sided p = 0.036). The 12-year incidence of PC central-reviewed deaths were 2.3% for RT + AAT and 7.5% for RT + placebo ( p< 0.001).The cumulative incidence of metastatic PC at 12 years was less in the RT + AAT arm, 14% (51 patients), vs. 23% (83 patients) in the RT + placebo arm (p < 0.001). Subgroup analyses of the relative benefits of the addition of AAT to RT are planned and will be presented. Late grade III and IV toxicity were similar in the AAT and placebo arms. The combined grade III and IV toxicities for RT + AAT and RT + placebo were: bladder 7.0% vs. 6.7%, bowel 2.7% vs. 1.6%. Gynecomastia differed significantly by treatment arm, 70% vs. 11%. Conclusions: 24 months of AAT using 150mg bicalutamide daily during and after salvage RT significantly improved long term overall survival and reduced the incidence of metastatic PC and PC death. Support: NCI grants U10CA21661, U10CA180868, U10CA180822, and U10CA37422 and AstraZeneca. Clinical trial information: NCT00002874.