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10610 Background: The role for genetic testing (GT) for prostate cancer (PCa) patients (pts) has expanded to find pts with germline pathogenic variants (PV) for therapeutic opportunities given FDA-approvals for PARP inhibitors in metastatic PCa as well as understanding familial cancer risk and opportunities for tailored screening and risk reduction. The PROMISE Registry (NCT04995198) was set up as a genetic registry to partner with PCa pts for rapid access to a new standard of care given insurance coverage and clinical implementation were initially major barriers. A second goal is to characterize disease features and treatment outcomes to inform management and provide updates about novel therapeutic clinical trials, both of which remain important to rare genetic variant carriers. Methods: PROMISE is a US decentralized prospective PCa genetic registry initiated in 2021 with initial phase to enroll and provide clinical-grade germline genetic testing (30 gene cancer-specific panel) to 5,000 PCa pts to identify ~500 PCa pts with variants of interest (pathogenic variants, PV, and variants of uncertain significance, VUS) in DNA repair genes for long-term clinical follow-up of 15 years (LTFU). Here, we report the initial phase testing results and identification of the LTFU cohort. Study design and enrollment strategy have been reported separately. Results: Between 2021-2026, 7,275 pts with any stage PCa across 50 US states self-consented to PROMISE, of which 5,674 (78%) of pts completed genetic testing, indicating feasibility of patient-directed, decentralized enrollment. We have identified 495 (8.7%) pts for LTFU. Baseline data is reported for n=367 (Table 1, will be updated at time of presentation). The most frequently observed PV/LPV variants being in CHEK2 (25%) , BRCA2 (23%) , ATM (12%) , and BRCA1 (4.6%). At the time of PCa diagnosis, the majority of LTFU pts had non-metastatic disease, with 47% of pts with Gleason>7, median PSA of 5 ng/mL, and median time from diagnosis to PROMISE GT of 25 months. Conclusions: PROMISE is a nationwide decentralized PCa genetic registry that has completed initial goal to recruit 5,000 PCa pts to offer germline genetic testing and recruit a cohort of 500 for LTFU. Data about diagnosis characteristics are reported, and analysis of ongoing disease course, treatment response/outcomes and overall survival is being collected. Clinical trial information: NCT04995198 . Long-term follow-up participant demographics. Characteristic Overall, N = 367 Age at Diagnosis (yrs) 63 (57, 69) Race N = 361 (6, nr) Asian, American Indian or Alaska Native, Multiracial, Other 22 (6.0%) Black or African American 22 (6.0%) White 317 (86%) Disease State at Diagnosis N = 348 (19, nr) Metastatic 46 (13%) Non-metastatic 302 (87%) Time from Diagnosis to PROMISE GT (months) 25 (4, 82) Gleason Score N = 280 (87, nr) </= 7 148 (53%) >7 132 (47%) PSA At Diagnosis (ng/mL) 5 (0, 10) (88, nr) Subjects with baseline data entered. nr=not reported. Median (Q1, Q3); n (%).

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

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.

PURPOSE Randomized clinical trials (RCTs) have shown progression-free survival (PFS) benefits of metastasis-directed therapy (MDT) without androgen deprivation therapy for oligometastatic castration-sensitive prostate cancer (omCSPC). Most patients with bone metastatic (BM) omCSPC recur with additional bone disease after MDT. We hypothesized the BM-targeting alpha-emitter radium-223 dichloride (Ra223) could target subclinical bone disease and delay progression. METHODS This is an investigator-initiated, multicenter, open-label phase II RCT. Eligible men with recurrent omCSPC with ≥one bone metastasis (≤three on conventional imaging and/or ≤five on molecular imaging) were randomly assigned (1:1) to stereotactic ablative radiation (SABR) MDT alone or SABR MDT with Ra223 (six cycles). Primary end point was composite PFS. RESULTS From August 9, 2019, to March 2, 2023, 64 patients were randomly assigned, 33 to SABR MDT and 31 to SABR MDT/Ra223 balancing for key covariates. Most SABR MDT/Ra223 patients (87%) received six cycles of Ra223. The median PFS was 11.8 months with SABR MDT and 10.5 months with SABR MDT/Ra223 (adjusted hazard ratio [aHR], 1.42 [95% CI, 0.79 to 2.56]; P = .24). Seven patients (11%) experienced grade 3 treatment-related adverse events (no grade 4 or 5), 2 of 33 (6%) with SABR and 5 of 30 (17%) with SABR MDT/Ra223. Patients with high-risk (HiRi) pathogenic mutations in ATM , BRCA1/2 , RB1 , or TP53 had worse PFS (HR, 5.95 [95% CI, 1.83 to 19.3]; P = .003). Greater T-cell receptor (TCR) unique productive rearrangements were prognostic for improved PFS independent of the treatment arm (aHR, 0.45 [95% CI, 0.21 to 0.96]; P = .04). CONCLUSION Adding Ra223 to SABR MDT in BM omCSPC does not delay progression of disease. We provide evidence for an HiRi mutational signature and TCR repertoire as prognostic biomarkers in omCSPC treated with SABR MDT, highlighting the importance of collecting biological correlates in RCTs for omCSPC.

Indications for and implications of germline genetic testing (GGT) in patients with prostate cancer have expanded over the past decade, particularly related to precision therapies and management. GGT has become the standard of care for many cancers such as breast, ovarian, colorectal, pancreatic, and metastatic prostate cancer, and it is imperative that patients be offered timely and equitable access to testing as it can inform patient-physician shared decision making for management of the current cancer as well as anticipatory guidance for disease progression. Additionally, GGT guides screening for and prevention of secondary malignancies for the patient and cascade testing for at-risk family members. Here, we present data supporting the notion that clinicians should offer all patients with prostate cancer the opportunity to undergo comprehensive GGT for pathogenic germline variants known to be associated with familial cancer and/or known to have implications for treatment and management.

e17061 Background: ThePhase 3 VISION trial demonstrated that [177Lu]Lu-PSMA-617 prolonged overall survival (OS) in metastatic-castration resistant prostate cancer (mCRPC) patients who progressed on taxane-based chemotherapy and androgen receptor-signaling inhibitors (ARSi). The expanded access program (EAP) (NCT04825652) was opened to provide access to [177Lu]Lu-PSMA-617 for eligible patients until regulatory approval was obtained. The VISION trial required strict inclusion and exclusion criteria, which may not represent the patient population encountered in clinical practice. This study aimed to evaluate the efficacy and safety profile of [177Lu]Lu-PSMA-617 in a real-world setting within the EAP and compare the results with those from the VISION trial. Methods: Patients enrolled in the EAP between May 2021 and March 2022 at four institutions in the United States with available toxicity and outcome data were included. Outcome measures included overall survival (OS), ≥50% PSA decline rates (PSA-RR), and incidences of toxicity according to Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Differences in baseline characteristics, toxicity, and PSA-RR between the EAP and VISION were evaluated using a t-test of proportions. Results: 117 patients with mCRPC were eligible and included. Patients enrolled in the EAP were similarly pretreated with taxane-based chemotherapy regimens (>1 taxane: 47% vs 40%; p=0.16) and more heavily pretreated with ARSi (>1 ARSi: 70% vs 46%; p<0.001). EAP patients had similar levels of ≥3 grade anemia (18% vs 13%; p=0.15), thrombocytopenia (13% vs 8%; p=0.13), and neutropenia (3% vs 3%; p=0.85) and higher levels of ≥3 grade lymphopenia (34% vs 8%; p<0.001). Patients treated within the EAP experienced numerically shorter OS (median OS: 13.7 vs 15.3 months) and similar PSA-RR (40% vs 46%; p=0.29). Median follow-up was numerically shorter in the EAP compared with VISION (14.7 mo vs 20.3 mo). Conclusions: mCRPC patients treated with [177Lu]Lu-PSMA-617 in a real-world setting were more heavily pretreated with ARSi, had a similar safety profile, and experienced numerically shorter OS and similar PSA-RR compared with VISION trial patients. A major limitation of this study is that we did not have access to individual patient data from the VISION trial, so we were not able to assess whether differences in OS between VISION and the EAP were statistically significant.

5074 Background: Analysis of phase 3 studies of patients (pts) with mHSPC in the era of ADT, including in combination with docetaxel and/or androgen receptor axis targeted therapies have established PSA-7mo as a key prognostic marker. Our objective was to evaluate the association between PSA-3mo, PSA 7-mo and OS measured in the phase 3 S1216 trial in mHSPC comparing ADT + orteronel (treatment arm) vs ADT + bicalutamide (control arm) [NCT01809691]. Methods: Pts enrolled in the S1216 trial with available PSA-3mo & PSA-7mo were included in this analysis. PSA responses were defined as complete response (CR) if PSA ≤ 0.2 ng/mL, partial response (PR) for PSA >0.2 and ≤ 4ng/mL, and no response (NR) as PSA >4 ng/mL at month 3 or 7. Landmark OS was measured and Cox regression model applied adjusting for stratification (performance status, extent of disease, early vs late start of treatment, treatment arm). Results: 1251 pts were alive and evaluable for PSA-3mo and 1231 pts were evaluable at 7 mo, out of a total of 1279 pts. The median age was 67 (range: 43-92), 10% of patients were black, 96% had a Zubrod performance status of 0-1. Median PSA at baseline was 29 ng/ml (range: 2-6710). Of pts on treatment vs.control arm, PSA-3mo CR, PR, and NR occurred in 52% vs 35%; 31% vs 42%, and 17% vs 23%, respectively. Of pts on treatment vs control arm, PSA-7mo CR, PR, and NR occurred in 61% vs 46%, 20% vs 26%, and 19% vs 29%, respectively. CR or PR at either timepoint led to significantly better outcomes than those with NR. No interaction between treatment arm and PSA response was observed in terms of OS. Conclusions: PSA-3mo and PSA-7mo are strong prognostic markers for pts with mHSPC. More pts on ADT with orteronel achieved CR at 3 and 7 mo. In addition to its use in counseling patients in the clinic, PSA-3mo and PSA-7mo may be used as parameters for designing future trials in pts with mHSPC, utilizing the next generation of intensification or de-intensification treatment regimens. Clinical trial information: NCT01809691 . [Table: see text]

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co‐primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. The initial STOMP and ORIOLE trial reports suggested that metastasis-directed therapy (MDT) in oligometastatic castration-sensitive prostate cancer (omCSPC) was associated with improved treatment outcomes. Here, we present long-term outcomes of MDT in omCSPC by pooling STOMP and ORIOLE and assess the ability of a high-risk mutational signature to risk stratify outcomes after MDT. The primary end point was progression-free survival (PFS) calculated using the Kaplan-Meier method. High-risk mutations were defined as pathogenic somatic mutations within ATM, BRCA1/ 2, Rb1, or TP53. The median follow-up for the whole group was 52.5 months. Median PFS was prolonged with MDT compared with observation (pooled hazard ratio [HR], 0.44; 95% CI, 0.29 to 0.66; P value < .001), with the largest benefit of MDT in patients with a high-risk mutation (HR high-risk, 0.05; HR no high-risk, 0.42; P value for interaction: .12). Within the MDT cohort, the PFS was 13.4 months in those without a high-risk mutation, compared with 7.5 months in those with a high-risk mutation (HR, 0.53; 95% CI, 0.25 to 1.11; P = .09). Long-term outcomes from the only two randomized trials in omCSPC suggest a sustained clinical benefit to MDT over observation. A high-risk mutational signature may help risk stratify treatment outcomes after MDT.

5025 Background: Prospective reports suggest metastasis directed therapy (MDT) in oligometastatic castration sensitive prostate cancer (omCSPC) is associated with improved treatment outcomes. Here we present long term outcomes of the phase II STOMP and ORIOLE trials and assess the ability of a high-risk (HiRi) mutational signature to provide prognostic and predictive information regarding MDT response. Methods: Patients with omCSPC (< 3 lesions) enrolled on STOMP (n = 62) and ORIOLE (n = 54) randomized to MDT or observation were pooled. The primary endpoint was progression-free survival (PFS) defined as either PSA or radiographic progression, initiation of androgen deprivation, or death. Secondary endpoint was radiographic PFS (rPFS) defined as radiographic progression or death. Both were calculated using the Kaplan-Meier method and stratified by treatment group. Next generation sequencing (NGS) was performed to identify a HiRi mutational signature defined as pathogenic mutations within ATM, BRCA1/2, Rb1, or TP53. Cox proportional hazards regressions were fit to calculate hazard ratios (HR) and assess the prognostic and predictive values of HiRi mutational status. Results: Median follow-up was 52.5 months. Median PFS was prolonged with MDT (11.9 months) compared to observation (5.9 months) with a pooled HR of 0.44 (95% CI, 0.29 – 0.66, p-value < 0.001). MDT was associated with PSA decrease in a majority of patients (84%) as compared to the observation group (41%). On NGS, the incidence of a pathogenic mutation in a HiRi gene was 24.3%. HiRi mutation was prognostic for PFS -- in those without a HiRi mutation median PFS was 11.9 months compared to 5.9 months in those with a HiRi mutation (HR of 1.74, p = 0.06). HiRi mutation was also prognostic for rPFS -- those without a high-risk mutation experienced median rPFS of 22.6 months compared to 10.0 months in those with a high-risk mutation (HR 2.62, p < 0.01). Tumors without a HiRi mutation treated with MDT experienced the longest PFS (13.4 months) while those with a HiRi randomized to observation experienced the shortest PFS (2.8 months). Stratifying by both treatment arms and HiRi status appeared to show a differential benefit to MDT, with those with HiRi mutations experiencing a larger relative magnitude of benefit to treatment: (HiRi mutation: HR of 0.05, p < 0.01; no HiRi mutation: HR of 0.42, p = 0.01; p interaction, 0.12) suggesting a HiRi mutational status can provide information regarding differential response to treatment. Conclusions: Long-term outcomes from the only two randomized trials in omCSPC suggest a sustained benefit to MDT over observation. A HiRi mutational signature appears prognostic for outcomes in omCSPC and those with HiRi might have a relatively larger magnitude of response to MDT. Future studies are needed to optimize patient selection. Clinical trial information: NCT02680587.

PURPOSE Orteronel (TAK-700) is a nonsteroidal 17,20-lyase inhibitor suppressing androgen synthesis. We evaluated the clinical benefit of orteronel when added to androgen deprivation therapy (ADT) in patients with newly diagnosed metastatic hormone-sensitive prostate cancer. METHODS In this open-label randomized phase III study, patients with metastatic hormone-sensitive prostate cancer were randomly assigned 1:1 to ADT with orteronel (300 mg oral twice daily; experimental arm) or ADT with bicalutamide (50 mg oral once daily; control arm). The primary objective was the comparison of overall survival (OS), targeting a 33% improvement in median survival. A stratified log-rank test with a one-sided P ≤ .022 would indicate statistical significance. Secondary end points were progression-free survival (PFS), prostate-specific antigen (PSA) level at 7 months (≤ 0.2 v 0.2 to ≤ 4 v > 4 ng/mL), and adverse event profile. RESULTS Among 1,279 patients included in the analysis, 638 were randomly assigned to the ADT plus orteronel arm and 641 to the control arm. The median age was 68 years; 49% had extensive disease. After a median follow-up of 4.9 years, there was a significant improvement in PFS (median 47.6 v 23.0 months, hazard ratio 0.58; 95% CI, 0.51 to 0.67; P < .0001) and PSA response at 7 months ( P < .0001), but not in OS (median 81.1 v 70.2 months, hazard ratio 0.86; 95% CI, 0.72 to 1.02; P = .040, one-sided). More grade 3/4 adverse events occurred in the experimental versus the control arms (43% v 14%). Postprotocol life-prolonging therapy was received by 77.4% of patients in the control arm and 61.3% of patients in the orteronel arm. CONCLUSION The study did not meet the primary end point of improved OS with orteronel. The lack of correlation of PFS and PSA response with OS raises concerns over assumption of their consistent surrogacy for OS in the context of extensive postprotocol therapy in this setting.