Bryce, Alan H.

ABSTRACT Background Men with castration‐resistant prostate cancer (CRPC) who have a pre‐existing history of cardiovascular disease (CVD) or other comorbidities are often excluded from clinical trials involving oral androgen receptor pathway inhibitors (ARPi). In this study, we compared all‐cause and prostate cancer‐specific mortality among CRPC patients, with and without a pre‐existing history of CVD, receiving ARPi compared to chemotherapy. Methods Men with CRPC were identified using the Surveillance, Epidemiology, and End Results‐Medicare Linked Database from 2004 to 2015. Patients were grouped into two analytical cohorts by drug use. Inverse probability treatment weights (IPTW)‐adjusted Cox models and Fine‐Gray subdistribution hazards models were used to evaluate associations between ARPi and chemotherapy, and between ENZ and AA for all‐cause mortality and cancer‐specific mortality separately. Results The study cohort included 1438 men with CRPC. Nearly 54.4% of patients had a pre‐existing history of CVD. Patients with a pre‐existing history of CVD had a higher incidence of all‐cause and prostate cancer‐specific mortality compared to patients without a history of CVD (all‐cause mortality: 69.7% vs. 59.3%, prostate cancer‐specific mortality: 56.0% vs. 49.5%, respectively). In the pre‐existing history of CVD cohort, the IPTW‐adjusted Cox model showed a significantly lower all‐cause mortality in patients who received APRi, enzalutamide, and abiraterone, versus chemotherapy (IPTW‐adjusted hazard ratio [AHR], 0.56; 95% Confidence Interval [CI], 0.48–0.64; p ‐value < 0.001). Further, the IPTW‐adjusted competing risk model showed significantly lower prostate cancer‐specific mortality in patients who received ARPi compared with those who received chemotherapy (IPTW‐AHR, 0.48; 95% CI, 0.41 to 0.57; p ‐value < 0.001). In the without pre‐existing history of CVD cohort, the adjusted Cox model showed significantly lower all‐cause mortality in patients who received APRi than those who received chemotherapy (IPTW‐AHR, 0.49; 95% CI, 0.41–0.60; p ‐value < 0.001). Whereas the IPTW‐adjusted competing risk model showed significantly lower prostate cancer‐specific mortality in patients who received ARPi compared with those who received chemotherapy (IPTW‐AHR, 0.52; 95% CI, 0.42–0.64; p ‐value < 0.001). Conclusion In this population‐based cohort of older men with castration‐resistant prostate cancer, treatment with oral androgen receptor pathway inhibitors was associated with lower estimated risks of all‐cause and prostate cancer–specific mortality compared with chemotherapy in patients with and without pre‐existing CVD. These findings add real‐world comparative effectiveness evidence for patient populations not well represented in randomized clinical trials; however, given the observational design and limitations of administrative data, residual confounding and unmeasured clinical differences may have influenced the results.

5054 Background: Rucaparib significantly improved radiographic progression-free survival (rPFS) versus physician’s choice of docetaxel or an androgen-receptor pathway inhibitor (ARPI) (abiraterone or enzalutamide) in men with BRCA mutations who were chemotherapy-naïve in the mCRPC setting and had received one prior ARPI in the phase 3 TRITON3 trial (NCT02975934). This post-hoc analysis evaluated whether the timing of prior ARPI therapy impacted the efficacy of rucaparib. Methods: Patients were randomized 2:1 to rucaparib (600 mg BID) or physician’s choice of docetaxel or ARPI, after progression on 1 prior second-generation ARPI in any setting. The primary endpoint was rPFS. Outcomes were analyzed according to whether patients received the prior ARPI in the metastatic castration sensitive (mCSPC) or castration resistant (mCRPC) setting. Data cutoff was August 25, 2022. Results: Of the 302 BRCA1/2 patients, 68 received prior ARPI in the mCSPC setting (42 rucaparib; 26 physician’s choice) and 234 in the mCRPC setting (159 rucaparib; 75 physician’s choice). Baseline characteristics were generally similar. Prior treatments in the mCSPC and mCRPC groups, respectively, included abiraterone (73.5% vs 53.0%), enzalutamide (29.4% vs 48.3%), and docetaxel (17.6% vs 24.8%). Median rPFS favored rucaparib over physician’s choice in both groups (mCSPC: 13.6 vs 8.2 months; HR 0.60 [95% CI, 0.32–1.15]; mCRPC: 11.2 vs 5.8 months; HR 0.43 [95% CI, 0.30–0.61]). Median OS was similar between treatments in both settings (mCSPC: 23.2 vs 21.7 months; HR 0.81 [95% CI, 0.47–1.41]; mCRPC: 23.2 vs 21.0 months; HR 0.91 [95% CI, 0.66–1.25]). Treatment-related adverse events occurred at comparable rates (89.6% vs 86.1%). Conclusions: Rucaparib demonstrated efficacy in patients with BRCA-mutated mCRPC, regardless of whether prior ARPI was administered in the mCSPC or mCRPC setting. Clinical trial information: NCT02975934 .

Abstract Purpose: This multicenter, single-arm, phase II trial evaluated the safety and efficacy of cabazitaxel and carboplatin followed by abiraterone, plus androgen deprivation therapy (ADT), in patients with high-volume metastatic castration-sensitive prostate cancer (mCSPC). Patients and Methods: Eligible patients had high-volume mCSPC and ≤3 months of prior ADT. Patients received six 21-day cycles of cabazitaxel (20 mg/m2) and carboplatin (AUC 4) with continuous ADT, followed by maintenance abiraterone (1,000 mg daily) and prednisone (5 mg daily). The primary endpoint was the proportion of patients free of prostate-specific antigen (PSA) or radiographic progression at 12 months. Secondary endpoints included complete PSA response (≤0.2 ng/mL), objective response, progression-free survival (PFS), and safety. Overall survival (OS) was also reported. Results: Sixty-one participants were enrolled at eight sites. The median age was 64 years, median baseline PSA was 6.6 ng/mL (0.07–745.7 ng/mL), 73.3% had Gleason grade group 5, 69.5% had 10 or more metastases, and 19.6% had a homologous recombination repair (HRR) mutation. PSA PFS at 12 months was 84.6% [95% confidence interval (CI), 72.5%–91.7%], and OS at 12 months was 94.8% (84.7%–98.3%). Complete PSA response was 66.7%, and complete objective response was 30.7%. Contrary to our hypothesis, relative to HRR wild-type patients, HRR-mutated patients (19.6%) had numerically fewer complete PSA responses (33.3% vs. 70.3%) and inferior PFS (HR, 2.43; 95% CI, 0.93–6.39). Common side effects of this quadruplet regimen included fatigue, nausea, and diarrhea. Conclusions: Cabazitaxel and carboplatin followed by abiraterone, together with ADT, were feasible, safe, and efficacious in patients with high-volume mCSPC and warrant further study in larger randomized trials.

46 Background: Primary results from the randomized, multicenter, open-label, phase 3 TRITON3 (NCT02975934) study demonstrated that rucaparib significantly improved radiographic progression-free survival (rPFS) vs physician’s choice of DTX or an ARPI. ECOG PS is used as a predictor of prostate cancer survival. In this post hoc analysis, we report results from the BRCA1/2 subgroup of pts stratified by ECOG PS. Methods: Pts with disease progression after 1 prior second-generation ARPI in any setting were randomized 2:1 to rucaparib 600 mg BID or physician’s choice of DTX or ARPI (abiraterone acetate or enzalutamide). Primary endpoint was rPFS by independent radiology review (IRR). Objective response rate (ORR) for pts with measurable disease and overall survival (OS) were key secondary endpoints. Crossover from physician’s choice to rucaparib was allowed after radiographic progression was confirmed by IRR. Data cutoff was August 25, 2022. Results: Of 302 pts in the BRCA1/2 population, 147 had an ECOG status of 0 (97 rucaparib; 50 physician’s choice) and 155 had ECOG 1 (104 rucaparib; 51 physician’s choice). Baseline characteristics and demographics were generally similar between arms for pts in the ECOG 0 and ECOG 1 groups. Median rPFS favored rucaparib vs physician’s choice for pts with ECOG 0 (11.4 vs 8.2 months; HR, 0.48 [95% CI, 0.30-0.76]) and ECOG 1 (10.9 vs 6.1 months; HR, 0.48 [95% CI, 0.31-0.74]) (Table). Additionally, rPFS favored rucaparib for ECOG 0 and ECOG 1 including those whose prespecified physician’s choice was ARPI or docetaxel (Table). The confirmed ORR (95% CI) of rucaparib vs physician’s choice for ECOG 0 was 54% (37%–69%) vs 16% (3%–40%); the ORR for ECOG 1 was 37% (22%–53%) vs 18% (5%–40%), respectively. Median OS was similar between arms for rucaparib or physician’s choice; median OS was 23.7 vs 21.7 months (HR, 0.91 [95% CI, 0.61–1.37]) for ECOG 0 and 21.8 vs 20.4 months (HR, 0.85 [95% CI, 0.58–1.24]) for ECOG 1. Conclusions: Rucaparib improved rPFS and ORR in pts with BRCA-mutated prostate cancer with an ECOG PS of 0 or 1. OS was similar for these groups in both arms. These data support rucaparib as a treatment option for pts with BRCA-mutated mCRPC, whether ECOG 0 or 1. Clinical trial information: NCT02975934 . Median rPFS in patients in the ECOG 0 and ECOG 1 groups. Rucaparib, n Physician’s choice, n rPFS Rucaparib, median months rPFS Physician’s choice, median months HR (95% CI) rPFS, ECOG 0 97 50 11.4 8.2 0.48 (0.30–0.76) rPFS, ECOG 1 104 51 10.9 6.1 0.48 (0.31–0.74) rPFS, physician’s choice ARPI, ECOG 0 51 24 11.2 5.6 0.42 (0.22–0.78) rPFS, physician’s choice docetaxel, ECOG 0 46 26 11.5 8.8 0.49 (0.24–0.98) rPFS, physician’s choice ARPI, ECOG 1 52 17 11.2 4.5 0.33 (0.16–0.68) rPFS, physician’s choice docetaxel, ECOG 1 52 34 10.7 7.1 0.59 (0.34–1.01)

352 Background: Glucagon-like peptide 1 (GLP1) receptor expression in prostate cancer tissue has raised concerns that GLP1 receptor agonists (GLP1A) may influence tumor growth or progression. We compared prostate cancer severity at diagnosis among patients receiving GLP1A versus other glucose lowering therapies. Methods: A retrospective chart review identified patients who received GLP1A or alternative second-line glucose lowering agents (DPP4/SGLT2 inhibitors) and were subsequently diagnosed with prostate cancer. Patients receiving both drug classes were excluded. Baseline demographics (race, ethnicity, age), comorbidities (diabetes, myocardial infarction, peripheral vascular disease) concomitant medications (insulin, metformin, statins), appointments (within past year) and laboratory values (HbA1c, eGFR) at therapy initiation were recorded. Primary outcomes included Gleason grade group and metastatic presentation within three months of diagnosis. Propensity score matching balanced baseline characteristics between groups. Mann-Whitney U tests compared grade groups. Chi-square tests compared metastatic presentation, reporting odds ratios (OR) with 95% confidence intervals (CI). Multivariable logistic regression identified predictors of grade group (low-grade: 1-2; high-grade: ≥3) and metastatic presentation, reporting OR with 95% CI. A p value <0.05 indicated a significant association. Results: Of 260 propensity-matched patients (GLP1A: 130, comparison: 130), 87% were White and 95% were Non-Hispanic/Non-Latino in each group. Median HbA1c was 7% (IQR: 6.4-8) in GLP1A group versus 7.5% (6.2-8.5) in comparison group. Median eGFR was 75mL/min/1.73m 2 (IQR: 61.5-90.0) in GLP1A group versus 60.0 (52.0-80.5) in comparison group. High-grade disease occurred in 33 (25%) GLP1A patients and 37 (29%) comparison patients. Among patients with available imaging (GLP1A: 40; comparison: 32), metastatic presentation occurred in 7 (18%) GLP1A group and 7 (22%) comparison group patients. No significant differences were observed in grade group (GLP1A median: 2; IQR: 1-2 vs. comparison median: 2; 1-3; p=0.44) or metastatic presentation (OR: 1.32; 95%CI: 0.41-4.25; p=0.64) between groups. In multivariable analysis, higher HbA1c was associated with high-grade disease in GLP1A group (OR: 1.83; 95%CI: 1.07-3.35; p=0.03) while higher eGFR was associated with low-grade disease in the comparison group (0.97; 0.93-0.99; p=0.04). Conclusions: GLP1A use was not associated with prostate cancer grade or metastatic presentation at diagnosis compared to alternative glucose-lowering agents. However, the association between elevated HbA1c and high-grade disease in GLP1A patients suggests a potential impact of poor glycemic control on tumor biology. Prospective studies are needed to elucidate the relationship between metabolic dysregulation and prostate cancer severity.

162 Background: Clinical trial conduct in advanced prostate cancer has changed dramatically with the continued development of new imaging approaches, molecular phenotypes and genetic subtypes, prognosis assessments, and effective therapies across a range of disease states. This created a need to redefine terminology and best practices for clinical trials. Methods: We convened PCWG4, an international expert committee of multidisciplinary working groups, between 2016 and 2025 to update and expand PCWG2-3 recommendations based on emerging evidence and clinical trial data in an innovative biomarker and imaging context to provide guidance for clinical trial design, eligibility, and endpoint assessments. Results: PCWG4 redefines terminology around disease states and prior therapies in a patient-centric context, considering imaging modalities, with a particular focus on PET-defined disease. New recommendations are provided for disease state terminology, defining eligibility criteria, imaging and non-imaging-based responses. We define delay/prevent endpoints including responses by pathology, ctDNA, circulating tumor cells, and PSA declines, and specify intervals for re-assessments including imaging, biomarker assessments, and patient reported outcomes. We propose new imaging-specific rPFS criteria including guidance with serial PSMA PET/CT imaging (Table). We provide recommendations in a biomarker-based context for the indication, reflective of patient benefit for specific interventions. We emphasize the need for development of validated PET imaging and molecular and phenotypic criteria as well as trial designs to appropriately risk stratify patients, predict and assess benefit, and measure post-treatment outcomes reliably in a trial framework. Conclusions: PCWG4 expands guidance on patient and tumor profiling, as well as therapy development, to include both androgen deprivation therapy sensitive and resistant settings, reflecting today’s more heterogeneous and diverse patient population to optimize outcomes. PCWG4-defined radiographic progression by imaging modality for patients with metastatic disease. Pretreatment Scan On-treatment Scan #1(≥week 8) On-treatment Scan #2 All Subsequent Scans Bone scintigraphy Comparator Comparator for subsequent scansPOD never called here POD:PCWG3 criteria (2+2 additional new lesions) POD:≤5 new lesions: PCWG3 criteria 2 new lesions confirmed≥6 new lesions CT/MRI Any measurable disease Comparator PCWG3/RECIST PCWG3/RECIST PCWG3/RECIST PSMA PET Bones, and lymph nodes and lung metastases (non-RECIST qualifying by + on PET only) Comparator POD:≤5 new lesions: 2 new lesions confirmed on a subsequent scan≥6 new lesions Same as prior Same as prior Liver and non-pulmonary viscera Comparator POD:Any single new lesion that represents disease Same as prior Same as prior

144 Background: Androgen receptor pathway inhibitors (abiraterone acetate [AAP], apalutamide [APA], enzalutamide [E], darolutamide [DARO] have become the cornerstone for pts with PCa due to survival benefits. Comparative data on fracture risk among ARPi are limited. This study quantified the risk of bone fractures with ARPi plus androgen deprivation therapy (ADT) and compared fracture risk across different ARPi agents. Methods: MEDLINE and EMBASE were searched from inception through September 1 st 2025 to identify positive phase III trials assessing ARPi in addition to ADT in pts with PCa (m0CRPC, mCSPC, mCRPC). Trials were included if they reported bone fractures in either arm. Pairwise, random-effects meta-analysis was conducted using Paul-Mendel approach. Sensitivity analyses using Hartung-Knapp (HK) adjustment was performed to assess robustness of results. To assess the comparative risk of bone fractures among different ARPi agents, mixed treatment comparisons were made using frequentist network meta-analysis. P-scores were computed to assess relative treatment rankings. Treatment effect was expressed as odds ratio (OR) with 95% confidence intervals (CI). Results: This systematic review included 13 phase III trials with 15468 pts (8890 received ARPi+ADT, 6578 received ADT alone). A total of 596 (6.7%) bone fractures were observed with ARPi+ADT compared to 180 (2.74%) with ADT alone. Patients receiving ARPi+ADT were associated with an increased risk of bone fractures compared to those receiving ADT (OR: 2.40; 95% CI: 1.93-2.98). Sensitivity analyses with HK adjustment showed consistent results (2.40; 1.88-3.06). There was no statistically significant effect modification by PCa clinical setting (p: 0.27). Mixed treatment comparisons showed a statistically significant increased risk of bone fractures with AAP+ADT (2.35; 1.29-4.27), APA+ADT (2.04; 1.47-2.86), and E+ADT (3.13; 2.44-4.00) but not with DARO+ADT (1.30; 0.80-2.08) when compared to ADT alone. Among different ARPi agents, E+ADT was associated with an increased risk compared to APA+ADT (1.54; 1.01-2.33) and DARO+ADT (2.44; 1.41-4.17). Ranking analysis showed that E+ADT was ranked as potentially the least safe treatment (P score: 0.05) in terms of relative fracture risk followed by AAP+ADT (P score: 0.30), APA+ADT (P score: 0.43), DARO+ADT (P score: 0.76). Sensitivity analyses limiting to mCSPC trials only showed consistent results. Conclusions: The risk of bone fractures varies among different ARPi agents, with enzalutamide posing the highest relative risk and darolutamide the lowest. These differences may guide treatment selection, particularly in pts with mCSPC and bone metastases. Prospective studies adjusting for covariates are needed to evaluate bone-protective strategies to mitigate fracture risk particularly in mCSPC patients who are considering treatment with ARPi.

127 Background: Bone metastases affect up to 90 % of patients with metastatic hormone-resistant prostate cancer (mHRPC) and cause substantial morbidity from skeletal-related events (SREs) such as fracture, spinal-cord compression, and palliative interventions. Bone-modifying agents (BMAs) including bisphosphonates and denosumab reduce SRE risk and are NCCN-recommended, however, real-world use remains inconsistent. Methods: Patients with mHRPC treated from January 2017-September 2024 across Mayo Clinic sites were identified using SQL-based EHR queries confirmed by manual chart review. Bone Metastases were detected through keyword searchers of radiology reports and confirmed through manual chart review. SRE-prevention dosing was defined as zoledronic acid 4mg IV or denosumab 120mg SC; osteoporosis dosing was excluded. SREs were identified using diagnosis codes and text-pattern searches for radiotherapy, surgery, fracture, and spinal-cord compression. Descriptive statistics summarized BMA utilization and SRE incidence. Categorical variables were compared using Chi-square tests, and a risk ratio (RR) with 95% confidence intervals was calculated to evaluate association between early BMA initiation and SRE risk. Results: Among 778 patients with mHRPC, 685 (88 %) had bone metastases (mean age 70.5 years). Of these, 169 (24.7 %) had an SRE, and 261 (38.1 %) received BMAs at SRE-prevention doses (denosumab n = 157 [60 %]; zoledronic acid n = 104 [40 %]). Based on a chi-square test, combined SRE incidence did not differ significantly (No BMA 23 %, denosumab 23 %, zoledronic 33 %; p = 0.069). Bone pain at baseline was more common in patients who later received a BMA (136 [68 %]) than in those who did not (82 [41 %]; p < 0.001). Among 200 randomly sampled non-BMA patients, 83 had no recorded BMA discussion (66 also lacked bone pain), 38 lacked dental clearance, 32 had uncompleted plans and 18 declined therapy. Early BMA initiation (before first bone metastases) was associated with fewer SREs (16 % vs 29 %; RR 0.56, 95 % CI 0.33–0.96). Conclusions: Less than half of bone-metastatic mHRPC patients received BMAs. Non-initiation was often linked to modifiable factors such as delayed dental clearance or lack of treatment discussions, highlighting the need for system-level strategies to improve timely bone-directed care. SREs were common, affecting one quarter of patients. Small sample size precluded meaningful comparison of the impact of BMAs on SRE incidence however early BMA initiation may lower SREs. Incidence of SREs stratified by no BMA vs BMA treatment. SRE No BMA BMA Overall Pathological Fracture 6.4% (27/424) 4.9% (13/261) 5.8% (40/685) Radiotherapy to Bone 13.9% (59/424) 18.8% (49/261) 15.7% (108/685) Spinal Cord Compression 0.7% (3/424) 3.1% (8/261) 1.6% (11/685) Surgery to Bone 2.1% (9/424) 0.3% (1/261) 1.5% (10/685) Combined 23% (98/424) 27.2% (71/261) 24.7% (169/685)

TPS290 Background: Landmark randomized trials established the survival benefit of adding D to ADT in mCSPC. Building on this foundation, subsequent trials (PEACE-1 and ARASENS) demonstrated further survival improvements when androgen receptor pathway inhibitors (ARPI) were added to the ADT + D backbone. However, the independent contribution of D within the triplet regimen remains unclear given lack of prospective evaluation. Additionally, tumor suppressor gene (TSG) alterations involving TP53, PTEN, and RB1 are frequently observed in PC and are associated with aggressive biology and poor outcomes, providing an opportunity to enhance prognostic accuracy and optimize selection of candidates for treatment intensification. We hypothesize that adding D to ADT plus A will improve survival compared to ADT + A in mCSPC and stratification by TSG status may identify different treatment effects across molecular subgroups. Methods: ASPIRE is an open-label, two-arm, randomized phase 3 study to assess the benefit of D added to ADT plus A for patients with mCSPC. Eligible patients include those with confirmed adenocarcinoma of the prostate with evidence of distant metastatic disease on conventional imaging and are appropriate to receive D. Patients with metachronous low-volume disease or PSMA-PET only disease are excluded. Candidates must have next-generation sequencing (NGS) results from a CLIA-certified tissue test available for TSG status stratification at registration. Eligible patients will receive ADT plus A (240 mg PO daily) +/- D for up to 6 cycles until progression of disease by PCWG3/RECIST version 1.1 criteria. Prior therapy with ADT (with or without ARPI) initiated within 120 days before registration is permitted. The primary endpoint is overall survival (OS). Secondary endpoints include OS by TSG status; radiographic progression-free survival (rPFS); time to castration resistance; symptomatic skeletal event–free survival; time to worsening of disease-related symptoms (NCCN-FACT FPSI-17); safety and tolerability (CTCAE v5.0); PSA90 response at 6 weeks and 6 months; time to PSA progression; and objective response rate in patients with measurable disease. The study will enroll 1200 patients and is currently actively accruing patients. Clinical trial information: NCT06931340 .

PURPOSE The continuous development of new imaging approaches, molecular phenotyping, genetic subtypes, prognosis assessments, and effective therapies across a range of disease states has created a need to redefine terminology and best practices for clinical trial conduct in patients with advanced prostate cancer. Methods We convened an international expert committee of diverse working groups, the Prostate Cancer Working Group 4 (PCWG4), between 2016 and 2025. Our objective was to formulate updated criteria based on emerging evidence and clinical trial data in a biomarker context to provide guidance for clinical trial design, eligibility, and end point assessments for patients with advanced prostate cancer. RESULTS PCWG4 redefines terminology around the disease state and previous therapies in a patient-centric context and terminology focused on androgen pathway modulation. We consider imaging, with a particular focus on positron emission tomography (PET)–defined disease. New recommendations are provided for disease state terminology, defining eligibility criteria, response and delay/prevent end points, intervals for reassessments including imaging, and patient-reported outcome determination. We provide recommendations in a biomarker-based context of use for the intended indication, reflective of patient benefit for specific interventions. We emphasize the need for development of validated PET imaging and molecular and phenotypic criteria as well as trial designs to appropriately risk stratify patients, predict and assess benefit, and measure post-treatment outcomes reliably in a trial framework. CONCLUSION PCWG4 updates recommendations on patient and tumor characterization, therapy development, and imaging criteria and extends guidance into earlier androgen pathway modulator–naïve/sensitive disease states to reflect an evolving, heterogeneous, and diverse patient population to optimize treatment benefits for all patients.