Citations

TPS909 Background: BCG-Exposed NMIBC (a high grade recurrence within 24 months of prior BCG, but not meeting “unresponsive” criteria) is a large patient population with a critical need for more effective treatment strategies that prevent the development of BCG unresponsive disease/progression. The current standard of care is re-treatment with BCG alone, but only ~50% of patients derive clinical benefit. While intravesical gemcitabine (with or without docetaxel) is sometimes used, multiple retrospective studies have found that GemDoce is no better than re-treatment with BCG alone for patients with BCG-exposed NMIBC. A chemoimmunotherapy strategy of intravesical Gemcitabine with BCG (GemBCG) combines the two most effective, inexpensive, and commonly used treatments for NMIBC. Based on compelling biologic rationale and preclinical data, a phase I/II (n=52) trial was initiated of GemBCG in BCG-exposed NMIBC (NCT04179162). GemBCG has minimal side effects (3.8% [2/52] with Grade 3 TRAEs (no grade 4/5 seen) with similar side effects and tolerability to BCG alone. GemBCG has a outstanding early efficacy signal (6-month complete response of 97% [28/29] in patients with CIS, compared to ~50% 6-month complete response w/ BCG alone for BCG exposed CIS). GemBCG has promising preliminary longer term efficacy (18-month HG-RFS of 76% compared to ~45-55% reported with BCG alone, GemDoce, and recombinant BCG in BCG exposed NMIBC). Correlative studies support the hypothesis that the addition of gemcitabine to BCG can favorably modulate the tumor immune microenvironment. Methods: Based on the above rationale, we initiated the “GAIN” trial (A032303/ NCT07000084), a prospective, multicenter, open-label phase III study for patients with BCG-exposed NMIBC randomized to either: re-treatment with BCG only (Arm A, SOC) or Gemcitabine + BCG (GemBCG, Arm B). BCG-exposed NMIBC is defined as a high grade NMIBC (Ta, T1, Tis/CIS) that has recurred within 24 months of prior BCG, but NOT otherwise currently meeting BCG unresponsive NMIBC. The primary objective is to compare high grade recurrence-free survival (HG-RFS) between the two treatment arms. Notable aspects of the trial include: (1) the reduced burden on investigators and research teams due to the NCI’s new streamlined data initiative, (2) liberal inclusion/exclusion criteria and pragmatic design to improve generalizability of results, and (3) Cystoscopic biopsies/TURBT at week 13/month 3 for all participants (both CIS and “papillary only”) for multiple reasons including to allow for earlier detection of BCG unresponsive disease for patient safety, increased rigor of the trial, and objectively evaluate urinary biomarkers/urinary tumor DNA. Clinical trial information: NCT04179162 .

TPS577 Background: Pembrolizumab (pembro) for one year following resection of localized high risk clear cell renal cell carcinoma (ccRCC) in a phase 3 trial resulted in improvement in relapse-free survival and overall survival (Choueiri, NEJM 2024). However, 20% of patients still experienced a relapse within 2 years with no biomarker yet identified to predict who will respond to or needs adjuvant therapy. Addition of a tyrosine kinase inhibitor (TKI) to immunotherapy (IO) is a standard of care in metastatic ccRCC, but to date no studies have addressed the addition of a TKI to IO in the adjuvant setting. Subsequently, phase 3 STRIKE! was developed to explore the benefit of 6 months of tivozanib (tivo) added to pembro vs pembro alone in the adjuvant setting for resected high risk ccRCC. Methods: Eligible patients have an ECOG performance status ≤2 and a histologically confirmed diagnosis of RCC with clear cell component with or without sarcomatoid features after complete resection of the primary tumor, with pathology revealing pT2 grade 4 disease or any grade ≥ T3 or TxN1. Patients are also eligible if they developed metastasis within a year after resection and then underwent resection, definitive radiation or ablation of solid, isolated, soft tissue metastases (excluding brain and bone lesions) with no evidence of active disease (M1NED). Patients will be randomized 1:1 to intravenous pembro for 48 weeks with or without the addition of tivo 1.34 mg by mouth daily D1-21 q28D for 6 months stratified by stage (T2T3 vs T4/N1 vs M1NED) . With no limit on dose holds or interruptions of tivo, dose reductions of tivo to 0.89 mg D1-21 q28D or tivo 0.89 mg every other day are allowed. No dose reductions of pembro are permitted. Following baseline imaging to confirm no disease, imaging is performed every 12 weeks for first year, every 16 weeks for second year, every 24 weeks for third year and then annually until 5 years after registration or progression. The primary endpoint will be disease-free survival (DFS) as assessed by investigator, with secondary endpoints being overall survival, safety and tolerability. The study will enroll 1040 patients to detect a minimum detectable hazard ratio of 0.67 (24-month DFS 84% in experimental arm) with 90% power. Quality of life analysis will compare global quality of life and fatigue between the two arms. Imaging and specimens will be banked for future research. The study opened to accrual in April 2025 and at this time 106 patients have enrolled. Clinical trial information: NCT06661720 .

LBA630 Background: Enfortumab vedotin (EV) + pembrolizumab (pembro) is the established first-line standard of care for locally advanced/metastatic urothelial carcinoma and represents a novel neoadjuvant and adjuvant treatment strategy for patients with muscle-invasive bladder cancer (MIBC) who are ineligible for cisplatin-based chemotherapy. The randomized phase 3 KEYNOTE-B15/EV-304 study (NCT04700124) evaluates neoadjuvant and adjuvant EV + pembro followed by radical cystectomy plus pelvic lymph node dissection (RC + PLND) vs neoadjuvant chemotherapy followed by RC + PLND in participants (pts) with MIBC who are eligible for cisplatin-based therapy. Methods: Pts with clinical stage T2-T4aN0M0 or T1-T4aN1M0 MIBC (confirmed by central pathology and central imaging assessment) who were eligible for cisplatin-based chemotherapy and RC + PLND were randomized 1:1 to receive either 4 cycles neoadjuvant EV 1.25 mg/kg IV on days 1 and 8 + pembro 200 mg IV on day 1 Q3W, followed by RC + PLND, and adjuvant 5 cycles EV + 13 cycles pembro (EV + pembro arm) vs 4 cycles neoadjuvant gemcitabine 1000 mg/m 2 on days 1 and 8 + cisplatin 70 mg/m 2 on day 1 Q3W, followed by RC + PLND (cis + gem arm). The primary endpoint was event-free survival (EFS) by blinded independent central review. Key secondary endpoints were pathological complete response (pCR) rate by blinded central pathological review and overall survival (OS). Safety was a secondary endpoint; AEs of special interest were based on distinct prespecified lists for each drug. Results: A total of 405 and 403 pts were randomized to EV + pembro and cis + gem, respectively. Median time from randomization to the data cutoff date of October 27, 2025 was 33.6 months (range, 22.5–53.6). Baseline characteristics were generally balanced between groups. EV + pembro significantly improved EFS (median NR vs 48.5 mo; 24-mo estimated EFS rate 79.4% vs 66.2%; HR 0.53, 95% CI 0.41–0.70; 1-sided P <.0001), OS (median NR vs NR; 24-mo estimated OS rate 86.9% vs 81.3%; HR 0.65, 95% CI 0.48–0.89; 1-sided P =.0029), and pCR rate (55.8% vs 32.5%; estimated difference 23.4%, 95% CI 16.7–29.8; 1-sided P <.0001) vs cis + gem. Grade ≥3 treatment-emergent AEs occurred in 75.7% of pts with EV + pembro and 67.2% with cis + gem. Most common grade ≥3 drug-related AE of special interest for EV was skin reactions (14.1%); most common grade ≥3 AE of special interest for pembro was severe skin reactions (13.9%). Conclusions: Neoadjuvant and adjuvant EV + pembro significantly improved EFS, OS, and pCR rate compared with neoadjuvant gem + cis in pts with MIBC who were eligible for cisplatin-based chemotherapy. The safety profile of EV + pembro was consistent with prior experience with the combination. These results support EV + pembro as an effective perioperative treatment option in this setting. Clinical trial information: NCT04700124 .

LBA629 Background: Whether BCG strain influences clinical efficacy is unclear. BCG shortages and a reliance on a single strain may impact disease outcomes. Evidence also suggests that priming with intradermal (ID) BCG vaccination prior to intravesical (IVe) BCG enhances anti-tumor immunity and cancer clearance. Co-primary objectives address these issues. Methods: The trial design calls for 924 eligible patients with BCG naïve non-muscle invasive bladder cancer (NMIBC) (HG Ta/T1 +/- CIS or CIS alone) with negative purified protein derivative (PPD) to be randomized in a 1:1:1 ratio, to IVe TICE (Arm 1), IVe Tokyo-172 (Arm 2), or ID + IVe Tokyo-172 (Arm 3) BCG, stratifying on age group and clinical stage. IVe BCG included 6 weekly instillations (induction) and three weekly instillations (maintenance) at 3 and 6 months (mo), then every 6 mo for 3 years. Objective 1 tests whether Tokyo-172 BCG is non-inferior (NI) to TICE BCG, specifying a NI hazard ratio=1.34 (84% power). Objective 2 tests whether priming with ID prior to IVe Tokyo-172 is superior to IVe Tokyo-172 (HR=0.71, 83% power). The primary endpoint is high-grade recurrence-free survival (HG-RFS) censored at last cystoscopy, using a one-sided α=0.021 for each test. A Cox model adjusting for the stratification factors is used. Secondary endpoints include adverse events, 6-mo biopsy-proven complete response (CR) in patients with CIS +/- Ta, T1, duration of CR, PPD conversion and HG-RFS, progression-free survival (PFS) and quality of life. Max follow-up is 5 years. Results: 1000 (984 eligible) patients were enrolled from 2/17-12/20. Median (IQR) follow up is 4.6 (3.6, 5.0) yrs. Median age (range) is 70 yrs (26, 99), 17% are female, 9% are non-white, and 34% had CIS at entry. HG-RFS, CR, duration of CR at 4 yrs, and PFS were similar among arms (Table). PPD conversion occurred in 29% and was not correlated with HG-RFS. Gr 1-2 AE rate was similar (67%, 71%, and 67%) and Gr 3-4 (no Gr 5s) rate was 6%, 11%, and 14% for Arms 1,2, and 3, respectively. Conclusions: Tokyo-172 is non-inferior to TICE BCG in terms of HG RFS and CIS CR and is similar for PFS. Gr 3-4 AE rate is higher with Tokyo-172. Priming with Tokyo-172 BCG does not improve HG RFS. PPD conversion is not prognostic. Clinical trial information: NCT #03091660 . CIS Component N (eligible) 5-yr HG RFS HG RFSHR (95.8% CI) @ 5-yrPFS PFS HR(95% CI) @ CR %(95% CI) 4 yr CR duration Tice Ive 333 (330) 58% 79% 62%; 71/114(53%, 71%) 80% Tokyo Ive 332 (327) 64% *0.82(0.63, 1.08) 79% *0.99(0.70, 1.39) 60%; 66/110(50%, 69%) 83% Tokyo ID + Ive 335 (327) 63% **1.00(0.76, 1.33) 77% **1.07(0.76, 1.51) 63%; 69/109(54%, 72%) 80% 3 mo. PPD + conversionY vs. N 782 evaluable225 (29%)557 (71%) 69%67% ^HR=0.91(0.68, 1.22) * Tokyo-172 vs. Tice, ** Tokyo Priming vs. Tokyo no priming. ^conversion to PPD + vs. – @ adjusted for 2 strat factors (and arms for PPD model). PFS event = MIBC, metastasis, or death.

98 Background: Circulating tumor DNA (ctDNA) monitoring provides an additional clinical tool for assessing treatment response and emerging resistance. We evaluated the real-world (RW) use and results of FoundationOne Monitor (F1Monitor), a tissue-free ctDNA monitoring assay, in patients (pts) with prostate cancer (PCa). Methods: The clinical laboratory developed test, F1Monitor, was available to physicians in a limited pilot with full discretion of test eligibility, timing, and frequency. Therapy type was a non-mandatory field on the order form. CtDNA was detected and quantified by ctDNA tumor fraction (TF); variants were tracked with variant allele frequency (VAF), and the origin [tumor somatic (TS), germline, or clonal hematopoiesis (CH)] was predicted algorithmically. Results: F1Monitor was ordered by 28 physicians for 215 pts with PCa. Therapy data were known for 156 pts: ADT+ androgen receptor pathway inhibitor (ARPI, N = 69/156 pts, 44%), ADT alone (N = 32, 21%), ADT + chemotherapy (chemo, N = 20,13%), ADT + radioligand therapy (RLT, N = 17, 11%), and others (N = 18). Median follow-up was 188 days. Longitudinal testing (≥2 tests) occurred in 64 pts, often (N = 37) when the first test was ctDNA TF positive (+). Median cadence for serial testing (≥3 tests, N = 31) was 42 days (IQR: 35, 59). ctDNA TF was + at any timepoint in 50% (107/215) of pts overall and 53% (82/156) of pts known to be on therapy, trending higher in pts on ADT+chemo (80%) and ADT+RLT (65%). Median and maximum ctDNA TF values were 11% (IQR: 0.9,37.8%) and 89% respectively. Lowest ctDNA TF and reportable TS VAF quantified were 0.13% and 0.04%, respectively. ctDNA TF longitudinal changes were observed in 67% (43/64) of pts: 92% of pts on ADT+chemo, 69% on ADT+RLT, 59% on ADT+ARPI, and 38% of pts on ADT alone. Among pts with ≥2 tests, 39% (25/64) had ctDNA TF increase, including 6/27 (22%) pts that were ctDNA TF negative (-) on the first test. Of pts with ≥2 tests and any ctDNA TF+ result, 35% cleared ctDNA TF in later tests. 33% of pts were persistently ctDNA TF -. Each test reported an average of 5 alterations: ~2 TS short variants, copy number variants, or rearrangements, and ~2 predicted CH variants. HRR variants were detected in 37% (80/215) of pts (31 with ≥2 tests) : persistent in 20 pts, cleared in 7, and newly emerging in 14. At least 50% of alterations in CHEK2 and ATM were predicted CH. Alterations in PI3K pathway genes were detected in 20% (43/215) of pts: (16 with ≥2 tests) persistent in 6 pts, cleared in 5, and newly emerging in 5. Conclusions: In this RW pilot of tissue-free ctDNA monitoring in PCa, F1Monitor demonstrated high sensitivity in clinical practice, detecting ctDNA TF as low as 0.13% and TS VAF as low as 0.04% while distinguishing tumor-derived from predicted CH variants. Importantly, ctDNA TF was + in 53% of pts while on therapy with observed longitudinal changes for 67% of pts, supporting potential utility of ctDNA for monitoring treatment response and emerging resistance.

88 Background: The VISION (NCT03511664) and PSMAfore (NCT04689828) clinical trials have demonstrated the effectiveness of 177 Lu-PSMA-617 in patients with mCRPC who have previously received androgen receptor pathway inhibitors (ARPIs) with or without taxane-based chemotherapy. Sipuleucel-T is used for treatment of mCRPC in routine clinical practice, particularly among community urologists; however, to date, there are no data available to understand the effectiveness of 177 Lu-PSMA-617 in patients previously treated with sipuleucel-T. Methods: This was a retrospective, observational study of adult patients with a diagnosis of mCRPC who received 177 Lu-PSMA-617 between March 23, 2022, and June 27, 2025, and had a history of treatment with sipuleucel-T. Data were obtained from the PRECISION data platform, a harmonized dataset of patients with advanced prostate cancer in the US that integrates electronic health records and claims data from community, academic, urology, and medical oncology settings. The index date was the date of 177 Lu-PSMA-617 initiation. Patient characteristics and prostate-specific antigen (PSA) response rates were evaluated descriptively. Progression-free survival (PFS), defined as the time from 177 Lu-PSMA-617 initiation to disease progression or death, was analyzed using Kaplan–Meier curves. Results: A total of 290 patients met the inclusion criteria, of whom 72% were White and 12% were Black. At index, 32% of patients were treated in urology and 68% in oncology settings. The median age was 74 years, the median baseline PSA was 35.3 ng/mL (interquartile range [IQR] 10.0–99.2 ng/mL), and 57% of patients had a Gleason score of ≥8. In addition to sipuleucel-T, prior to 177 Lu-PSMA-617, 97% of patients had received ≥1 ARPI and 79% had received ≥1 taxane. The median follow-up for this cohort was 9.4 months (IQR 5.3–17.5 months). Among 144 patients with available PSA values both before and during 177 Lu-PSMA-617 treatment (representing 50% of the cohort), PSA response rates were as follows: a ≥50% reduction in PSA from baseline (PSA50) was observed in 60%, PSA80 in 42%, and PSA90 in 33% of patients. Overall, the median PFS was 15.2 months (95% confidence interval [CI] 11.6–19.4 months). Conclusions: In this real-world analysis of patients who received 177 Lu-PSMA-617 after sipuleucel-T treatment, the median PFS was similar to that observed in clinical trials, suggesting that 177 Lu-PSMA-617 can be sequenced after sipuleucel-T treatment in appropriate patients.

81 Background: In the PSMAfore clinical trial, 177 Lu-PSMA-617 achieved a PSA50 (defined as a ≥50% reduction in prostate-specific antigen [PSA] from baseline) response rate in 58%, a median radiographic progression-free survival (PFS) of 12 months, and a median overall survival (OS) of 25 months among taxane-naïve patients with mCRPC who had received one prior androgen receptor pathway inhibitor (ARPI). The aim of the present study was to evaluate the real-world effectiveness of 177 Lu-PSMA-617 in taxane-naïve patients with mCRPC who had received one or more prior ARPIs. Methods: This retrospective, observational study included taxane-naïve adults with mCRPC initiating 177 Lu-PSMA-617 between March 23, 2022, and June 27, 2025, after ≥1 prior ARPI. All data for the study were extracted from the PRECISION data platform, a harmonized dataset of patients with advanced prostate cancer in the US treated in a variety of clinical settings. The index date was the date of 177 Lu-PSMA-617 initiation. Patient characteristics and PSA response rates were evaluated descriptively. PFS, defined as the time from 177 Lu-PSMA-617 initiation to progression or death, was estimated using Kaplan–Meier methodology. Results: A total of 500 patients were included. The median age was 75 years, 75% of patients were White and 8% Black, and 18% were treated in urology centers while 82% were treated in oncology centers. The most common site of metastasis was bone (77%), followed by lymph node (21%), visceral (12%), and unknown (5%). Overall, 51% had received 1 previous ARPI while 49% had received ≥2. The median baseline PSA was 26.7 ng/mL (interquartile range [IQR] 10−105 ng/mL) and the median time from mCRPC diagnosis to 177 Lu-PSMA-617 initiation was 23.6 months. The median number of 177 Lu-PSMA-617 cycles received was 4 (IQR 2−6). Among 219 patients with available PSA measurements both before and during 177 Lu-PSMA-617 treatment (representing 44% of the cohort), PSA response rates were as follows: PSA50 in 137 (63%), PSA80 in 86 (39%), and PSA90 in 56 (26%) patients. Overall, the median PFS was 13.5 months (95% confidence interval 11.7–14.7 months). Conclusions: The effectiveness of 177 Lu-PSMA-617 as a standard-of-care treatment in real-world, taxane-naïve patients with mCRPC who had received prior treatment with ≥1 ARPI is consistent with results from the PSMAfore trial, confirming the applicability of those findings to the real-world population now eligible for 177 Lu-PSMA-617. Further research on sequencing 177 Lu-PSMA-617 after one or more prior ARPIs in taxane-naïve patients with mCRPC is needed to guide optimal treatment sequencing in clinical practice.

794 Background: HER2 protein, encoded by ERBB2 gene, is the target of emerging therapies for patients (pts) with advanced urothelial carcinoma (aUC). High HER2 IHC expression (IHC 3+) is present in ~15% of pts with aUC, while >50% of pts have HER2 IHC 1+/2+/3+ expression. EVP is the preferred 1 st line regimen for pts with aUC, but the impact of HER2 status on EVP outcomes is unclear. Methods: We identified pts from the UNITE study with tumor samples tested for HER2 by IHC and another cohort with next-generation sequencing (NGS) data available. Outcomes were compared by HER2 IHC status (HER2 IHC 0/1+ vs 2+/3+) and separately based on ERBB2 status (alteration vs wild-type). X 2 test was used to compare observed response rate (ORR) and logistic regression was used to compare disease control rate (DCR). Duration of response (DOR), progression-free survival (PFS) and overall survival (OS) from EVP start were evaluated using log-rank test and Cox proportional hazards models. Multivariate analysis (MVA) included age, sex, race, ECOG PS, neutrophil:lymphocyte ratio, albumin, hemoglobin, primary tumor site, tumor histology, prior lines of treatment, and metastatic sites as covariates. Results: Among 521 pts treated with EVP from 16 sites, 112 had HER2 IHC data and 313 had NGS. Median age was 71, 74% were men, 84% Caucasian, 82% had ECOG PS 0-1, 65% pure urothelial histology, and 73% received frontline EVP. HER2 IHC distribution (n=112) was 27%/21%/37%/15% for 0/1+/2+/3+, respectively. ERBB2 alterations were present in 14% (44/313). Baseline characteristics were similar in HER2 0/1+ and 2+/3+ pts, except more primary bladder tumors in 2+/3+ pts (83% vs 63%, p=0.01). For the overall cohort (n=521), with a median follow up of 7.3 mos from EVP start, ORR was 54%, DCR 81%, median DOR (mDOR) 8.5 mos, median PFS (mPFS) 8.5 mos, and median OS (mOS) 19.8 mos. Pt outcomes by HER2 IHC status are shown (Table). In univariate analysis (UVA), pts with HER2 IHC 0/1+ had longer mOS compared to HER2 IHC 2+/3+, but this was not significant in MVA (HR: 0.5; CI: 0.2–1.3, p=0.17). No significant differences were observed in other outcomes. Evaluating clinical outcomes by ERRB2 status, no significant differences were seen for ERBB2 -altered vs wild-type pts. Conclusions: In this retrospective study, no significant differences were seen in EVP treatment outcomes based on HER2 IHC status or ERBB2 status. These findings are hypothesis-generating and require validation in larger and prospective cohorts. HER2 0/1+ (n=54)* HER2 2+/3+ (n=58) OR (95%CI, p) HR UVA (95%CI, p) HR MVA (95%CI, p) ORR 49% (23/47) 55% (27/49) 1.3 (0.6-2.9, p=0.5) - - DCR 79% (37/47) 88% (43/49) 1.9 (0.7-6.2, p=0.2) - - mDOR 11.7 mos 10.4 mos - 1.3 (0.7-2.4, p=0.4) 1.2 (0.4-3.3, p=0.8) mPFS 5.9 mos 7.1 mos - 0.8 (0.5-1.4, p=0.5) 1.1 (0.5-2.5, p=0.9) mOS 42.4 mos 18.7 mos - 2.3 (1.1-4.5, p=0.02) 2.0 (0.8-5.4, p=0.2) *HER2 0/1+ used as reference.

79 Background: In March 2025, the indication for 177 Lu-PSMA-617 was expanded to include prostate-specific membrane antigen (PSMA)-positive patients with mCRPC treated with ≥1 androgen receptor pathway inhibitor (ARPI) and considered appropriate to delay taxane-based chemotherapy. With 177 Lu-PSMA-617 moving earlier in the treatment journey, it is important to understand the clinical activity of other systemic therapies after 177 Lu-PSMA-617. The aim of this study was to evaluate the clinical outcomes among patients with mCRPC receiving a systemic therapy after 177 Lu-PSMA-617 treatment. Methods: This retrospective, observational study used real-world data from the PRECISION data platform, a proprietary dataset developed by Novartis representative of patients with advanced prostate cancer in the US from diverse clinical settings. Patients with mCRPC treated with 177 Lu-PSMA-617 who received a systemic therapy ≥14 days after treatment with 177 Lu-PSMA-617 between March 23, 2022, and June 27, 2025, were included. Systemic therapies included ARPIs (abiraterone, enzalutamide, darolutamide, apalutamide); chemotherapy (cabazitaxel, docetaxel, carboplatin, cisplatin, etoposide, mitoxantrone); immunotherapy (pembrolizumab, sipuleucel-T); poly (ADP-ribose) polymerase (PARP) inhibitors (niraparib, olaparib, talazoparib, rucaparib); and radium-223. Patient characteristics and prostate-specific antigen (PSA) response were evaluated descriptively. Progression-free survival (PFS) from subsequent therapy initiation was estimated using Kaplan–Meier methodology. Results: A total of 442 patients receiving any subsequent systemic therapy after 177 Lu-PSMA-617 were included. Overall, 95% of patients received ≥1 ARPI and 76% ≥1 taxane pre- 177 Lu-PSMA-617. The median age was 73 years. Most patients received a taxane (n = 188), an ARPI (n = 176), or a PARP inhibitor (n = 33) as their subsequent therapy. The median time to subsequent therapy initiation was 70 days (interquartile range 38−137 days) from the last 177 Lu-PSMA-617 administration. Among 299 patients receiving a systemic therapy after 177 Lu-PSMA-617 with PSA values available both pre-index and during subsequent treatment, 48% achieved a ≥50% reduction in PSA from baseline (PSA50), 31% a PSA80, and 18% a PSA90. The median PFS from the initiation of subsequent therapy was 8.6 months in the entire cohort; this was 10.7 months with a subsequent ARPI, 7.2 months with a subsequent taxane, and 7.1 months with a subsequent PARP inhibitor. Conclusions: In this real-world analysis, meaningful clinical responses were observed in a subset of patients who received subsequent systemic therapies after 177 Lu-PSMA-617.

78 Background: 177 Lu-PSMA-617 is currently under investigation in combination with an ARPI in those with metastatic hormone-sensitive prostate cancer (PSMAddition trial: NCT04720157). This observational study was performed to assess the effectiveness of 177 Lu-PSMA-617 in combination with an ARPI in patients with mCRPC in the real-world setting. Methods: This was a retrospective cohort study of adults with mCRPC in the PRECISION data platform, a comprehensive database of prostate cancer patients compiled from diverse clinical settings in the US. Patients who received 177 Lu-PSMA-617 during March 23, 2022–June 27, 2025 were identified, among whom two cohorts were selected for inclusion: those who had evidence of ARPI use (apalutamide, darolutamide, abiraterone, or enzalutamide) at any time during 177 Lu-PSMA-617 treatment (concomitant ARPI cohort), and those who had no other treatment for mCRPC during 177 Lu-PSMA-617 treatment (no concomitant therapy cohort). The index date was initiation of 177 Lu-PSMA-617. Patient characteristics and prostate-specific antigen (PSA) responses were evaluated descriptively. Progression-free survival (PFS), defined as the time from 177 Lu-PSMA-617 initiation to disease progression or death, was estimated using Kaplan–Meier analysis. Results: A total of 1,880 patients treated with 177 Lu-PSMA-617 were identified, 140 in the concomitant ARPI cohort and 1,740 in the no concomitant therapy cohort. The median age was 74 years. Demographic characteristics were balanced between the groups, except that median baseline PSA was lower in the concomitant ARPI cohort when compared with patients in the no concomitant therapy cohort (18 ng/mL vs. 32 ng/mL). Before 177 Lu-PSMA-617 initiation, 94.3% and 73.6% of patients in the concomitant ARPI and 80.9% and 56.7% in the no concomitant therapy cohort had received ≥1 prior ARPI and ≥1 prior taxane, respectively. PSA response rates were broadly comparable between cohorts. The median (95% confidence interval) PFS was 14.7 (11.7–21.3) months among patients in the concomitant ARPI cohort vs 12.5 (11.5–13.6) months in the no concomitant therapy cohort. Ongoing follow-up aims to evaluate the impact of combining ARPI with 177 Lu-PSMA-617 on long-term clinical outcomes, including overall survival. Conclusions: The results of this study demonstrate that 177 Lu-PSMA-617 delivers clinical benefits inpatients with mCRPC with or without ARPI; however, addition of an ARPI may potentially improve these benefits. Prospective randomized controlled studies are needed to confirm this.