Andrews, Jack R.

TPS272 Background: Prostate-specific membrane antigen (PSMA)-targeting positron emission tomography (PET) radiopharmaceuticals enable early detection of metastatic and recurrent prostate cancer (PCa). High urinary radioactivity of some PSMA-PET agents can affect interpretation of scans in the pelvic region (prostate/prostate bed [PB]; pelvic lymph nodes [PLN]). 18 F-Piflufolastat and 18 F-flotufolastat are FDA-approved, mainly renally cleared, diagnostic PSMA-PET agents; data suggest 18 F-flotufolastat has lower urinary radioactivity than 18 F-piflufolastat, but no clinical differences have been confirmed by head-to-head intra-patient studies. The present study will directly compare the urinary radioactivity of 18 F-piflufolastat with 18 F-flotufolastat in men with low prostate-specific antigen (PSA) biochemical recurrence (BCR) of PCa after radical prostatectomy (RP). Methods: This multicenter, prospective, intra-patient comparator study will include men (≥ 18 years old) with low PSA (≤ 0.5 ng/mL) BCR of PCa who have had RP ≥ 6 months before enrollment (with undetectable PSA post surgery) and are due to have routine 18 F-piflufolastat PET. Men who have had prior 18 F-piflufolastat PET or salvage therapy, or with conditions affecting urinary output, will be excluded. Eligible patients will undergo 18 F-piflufolastat PET followed by 18 F-flotufolastat PET ≥ 24 hours but ≤ 10 days later. No diuretic will be administered for scanning purposes. Each radiopharmaceutical will be administered as a single intravenous bolus per approved US prescribing information (USPI). Scanning (with the same scanner for both scans) will start 50–90 minutes post injection of 18 F-piflufolastat and 50–70 minutes post injection of 18 F-flotufolastat. Each patient will be their own control. The primary endpoint will be difference in mean standardized uptake value (SUV mean ) between 18 F-piflufolastat and 18 F-flotufolastat as assessed in volumes of interest drawn on the urinary bladder. Secondary endpoints for both agents will include detection rates: at the patient level (overall; by baseline PSA); for local recurrences in PB subregions; and for PLN lesions. For secondary endpoints, PET scans will be interpreted per product-specific USPI by 2 specially trained, blinded, central readers (a third reader will adjudicate disagreements). Safety will be monitored until 24 hours after the second scan. Around 60 men will be screened and ≥ 52 with evaluable PET scans for both agents will be included in the primary analysis. The primary endpoint will be assessed for normality and a difference in SUV mean will be tested using 2-sided paired tests (Wilcoxon signed-rank test [non-normal]; t-test [normal]). All further endpoints, including safety, will be summarized descriptively. The trial has been open for enrollment since 10/24. Clinical trial information: NCT06604442 .

112 Background: We now have more than a decade of experience using Androgen Receptor Pathway Inhibitors (ARPIs) across various disease states of prostate cancer, and the safety of their combination with Lutetium-177–PSMA-617 has been demonstrated in VISION and other large randomized clinical trials. However, real-world data on treatment patterns and outcomes involving combination therapies with 177 Lu-PSMA-617 remain limited. Methods: For this analysis, we utilized the Mayo Clinic Rochester radiopharmaceutical database, a prospectively maintained retrospective database containing all patients who received 177 Lu-PSMA-617 at our institution. We focused on patients who started treatment from March 2022 to March 2023. Patients receiving an ARPI (abiraterone acetate, enzalutamide, apalutamide, or darolutamide) during the course of 177 Lu-PSMA-617 treatment were identified, inclusive of patients who continued using an ARPI prescribed as a prior line of treatment and those who started (i.e., switched) to a new ARPI. Baseline clinicopathologic and imaging characteristics were abstracted and compared using the Mann-Whitney U and Chi-square tests. Best PSA response during treatment was reported as a percent decline from baseline. Survival was calculated from the date of the first cycle of 177 Lu-PSMA-617. PSA50 response and overall survival (OS) outcomes for the two groups (concurrent use of ARPI vs. 177 Lu-PSMA-617 alone) were compared using the Chi-square test and Kaplan-Meier method, respectively. A multivariate Cox regression analysis was performed, including established prognostic factors. Results: An ARPI was prescribed to 106 of the 256 patients (41.4%) starting 177 Lu-PSMA-617 in the interval of March 2022 to March 2023. With regards to baseline characteristics, those receiving an ARPI concurrently with 177 Lu-PSMA-617 had a lower PSA (3.4 vs 29.7 ng/mL, p < 0.001) and a lower frequency of bone (77.4% vs. 87.4%, p = 0.035) and visceral metastases (18.9 vs 34%, p = 0.008) at start of treatment. Median follow-up for the overall cohort (IQR) was 19.1 months (8.7 – 23.6). Patients receiving an ARPI plus 177 Lu-PSMA-617, as compared to 177 Lu-PSMA-617 alone, were more likely to complete all 6 planned doses of treatment (63.2% vs. 48.7%, p < 0.001), though the PSA50 response rate was similar (49.1% vs 47.3%, p = 0.786). Median OS [95% CI] for the overall cohort was 21.3 [16.7 – 25.9] months and significantly longer for those receiving ARPI with 177 Lu-PSMA-617 (NR [NE – NE]) as compared to 177 Lu-PSMA-617 alone (15.3 mo [11.6 – 19.1], p < 0.001). However, on multivariate analysis including known prognostic variables, use of ARPI was not independently associated with improved survival (HR = 1.03 [CI: 0.68 to 1.55], p = 0.891). Conclusions: Patients receiving an ARPI with 177 Lu-PSMA-617 were more likely to complete all 6 cycles of treatment, but no clear differences in survival were observed on multivariate analysis.

341 Background: Specialist clinicians (oncologists, urologists, radiation oncologists) read through free text reports of prostate MRI and biopsy reports to risk stratify patients during initial consultation of localized PCa. This laborious and time-consuming process is repeated for each day during the clinic. Herein, we propose a hybrid stratification framework utilizing a combination of large language model (LLM) and rule-based programming to automate this process. Methods: This retrospective study included patients with localized PCa (2004-2024) presenting to care at Mayo Clinic with at least one positive prostate biopsy and MRI report available. The state-of-the-art LLM – GPT4 – was utilized using a structured zeroshot prompt to extract relevant phenotypic variables (clinical T stage, Gleason patterns, grade group, extent of specimen/cores involved, prostate size/volume) from unstructured MRI and biopsy reports. Using a rule-based algorithm, the extracted variables and PSA at PCa diagnosis were used to categorize each patient into one of the six NCCN risk categories (very low [VL], low [L], favorable intermediate [FInt], unfavorable intermediate [UFInt], high risk (HR), very high risk [VHR]). Prompts were iteratively developed using ~5% of the total dataset and validated on ~10% of the dataset. Final performance was assessed against a held-out expert annotated test dataset using evaluation metrics (accuracy, F1-score, precision, recall). Additionally, manual annotation was conducted by two independent novice reviewers to compare machine annotated and novice-human annotated risk categorization. Results: A total of 397 patients were included in the evaluation. The median age at diagnosis was 64.8 (IQR: 59.7-68.5); majority of the men were White (n: 366; 92%) and non-Hispanic (n: 371; 94%). The most prevalent risk category was UFint (n: 151; 38%) followed by FInt (n: 80; 20.2%), HR (n: 76; 19.1%), VHR (n: 64; 16.1%), L (21: 5.3%), and VL (n: 5; 1.3%). Novice reviewers achieved an accuracy of 79%, precision of 80%, recall of 82% and a F1-score of 0.81. The hybrid stratification framework using GPT4 achieved an accuracy of 89%, precision of 89%, recall of 88% and a F1-score of 0.88. Among 43 errors by GPT4 risk stratification, majority of the errors were due to miscategorization of clinical T-stage (n: 21; 49%) followed by erroneous number of positive cores (n: 13; 30%). However, additional evaluation showed that GPT4 achieved numerically higher performance (accuracy: 90%; precision: 91%; recall: 90%; F1: 0.90) compared to novice reviewers (accuracy: 77%; precision: 89%; recall: 77%; F1: 0.82) for ascertaining clinical T-stage. Conclusions: Large language models exhibited superior performance than novice clinicians for risk stratification in patients with localized PCa. As the next step, we intend to validate our framework for automated risk classification in a prospective manner.

184 Background: We update evidence on mHSPC when new evidence becomes available (PMID: 36862387). ARANOTE trial prompted us to assess the comparative efficacy of darolutamide (DARO) with other ARPi agents in mHSPC using the living network meta-analysis (LNMA). Methods: This LNMA is conducted using the living interactive evidence (LIvE) synthesis framework. Phase III trials assessing systemic treatments in mHSPC are included. Mixed treatment comparisons were made using a frequentist network meta-analysis. P-scores were computed to assess relative treatment rankings with higher values indicating potentially better efficacy. Results: This report of LNMA includes a total 11 trials (12628 patients; 12 unique treatment options) as of October 1 st , 2024. Overall results were consistent with prior updates. Analysis limited to the ARPi trials showed that inhigh volume, abiraterone acetate (AAP)+androgen deprivation therapy (ADT) (HR: 0.46; 95% CI: 0.40-0.53; rank 1), apalutamide (APA)+ADT (0.53; 0.41-0.68; rank 3), DARO+ADT (0.60; 0.44-0.81; rank 4) and enzalutamide (E)+ADT (0.48; 0.41-0.56; rank 2) significantly improved radiographic progression-free survival (rPFS) compared to ADT alone. No statistically significant differences were observed with DARO+ADT compared to AAP+ADT (1.30; 0.94-1.82), APA+ADT (1.14; 0.77-1.67) and E+ADT (1.24; 0.89-1.79). Inlow volume, AAP+ADT (0.48; 0.37-0.63; rank 4), APA+ADT (0.36; 0.22-0.58; rank 3), DARO+ADT (0.30; 0.15-0.60; rank 1) and E+ADT (0.32; 0.25-0.41; rank 2) significantly improved rPFS compared to ADT. E+ADT significantly improved rPFS compared to AAP+ADT (0.67; 0.47-0.96) in low volume. No statistically significant differences were observed with DARO+ADT compared to AAP+ADT (0.62; 0.30-1.30), APA+ADT (0.83; 0.36-1.92) and E+ADT (0.93; 0.45-1.94). In synchronous disease, AAP+ADT (0.58; 0.51-0.67; rank 4), APA+ADT (0.49; 0.39-0.62; rank 2), DARO+ADT (0.59; 0.44-0.79; rank 3) and E+ADT (0.42; 0.36-0.50; rank 1) significantly improved rPFS compared to ADT. E+ADT significantly improved rPFS compared to AAP+ADT (0.73; 0.59-0.89) in synchronous disease. In metachronous disease, DARO+ADT (0.34; 0.17-0.67; rank 1), APA+ADT (0.41; 0.22-0.77; rank 2) and E+ADT (0.44; 0.35-0.57; rank 3) significantly improved rPFS compared to ADT. No statistically significant differences were observed with DARO+ADT compared to APA+ADT (0.83; 0.33-2.08) and E+ADT (0.76; 0.37-1.57) in metachronous disease. The results were consistent for overall survival. Conclusions: Current evidence suggests no significant differences for darolutamide as compared to other ARPi agents. Enzalutamide may be preferred over AAP in low-volume or synchronous disease. Given similar efficacy, choice of ARPi requires careful consideration of patient-specific factors including cost, accessibility and toxicity.

175 Background: 177 Lu-PSMA-617, a PSMA-directed radionuclide therapy, is an emerging treatment for metastatic castration-resistant prostate cancer (mCRPC). This retrospective study evaluates clinical outcomes of 177 Lu-PSMA-617 in low volume (LV) and high volume (HV) mCRPC, classified using the CHAARTED criteria. Methods: We conducted a retrospective review of the Mayo Clinic Prostate Cancer Registry, including mCRPC patients treated with 177 Lu-PSMA-617 at Mayo Clinic Rochester, MN, from August 2017 to August 2024. Patients were categorized based on CHAARTED criteria, which define high-volume disease by the presence of visceral metastases and/or four or more bone metastases, with at least one outside the vertebral column and pelvis. PSA-response rate (PSA-RR), overall survival (OS), PSA-progression-free survival (PSA-PFS), and radiographic progression-free survival (rPFS) were analyzed using Kaplan-Meier curves with log-rank tests, as well as uni- and multivariate Cox regression. Results: Of the 264 patients treated with 177 Lu-PSMA-617, 83 were classified as LV (median follow-up: 17.1 months) and 177 as HV (median follow-up: 13.7 months). LV patients had lower serum PSA levels (P < 0.0001), higher hemoglobin levels (P < 0.0001), and a longer time from diagnosis to treatment initiation (10.3 years vs. 7.2 years, P = 0.04). In the HV group, 92% had bone metastases, 60% had lymph node involvement, 54% had both, and 35% had visceral metastases. In the LV group, 64% had bone metastases, 84% had lymph node involvement, 25% had both, and none had visceral metastases. Median OS was 14.4 months for HV patients and 17.6 months for LV patients (P < 0.0001). Median PSA-PFS was 11.4 months for HV patients and 13 months for LV patients. Median rPFS was 9.1 months for HV patients and 10.6 months for LV patients. PSA-RR significantly differed between groups (P < 0.0001). In the HV group, 20% achieved CR (PSA < 0.2 ng/mL), 29% had PR (PSA decreased by ≥50%), 16% experienced SD, and 35% had PD (PSA increased ≥25% from nadir). In contrast, the LV group had 51% achieving CR, 10% achieving PR, 18% with SD, and 11% with PD. Conclusions: Lower disease volume in mCRPC is strongly associated with improved outcomes following 177 Lu-PSMA-617 therapy. These findings suggest that tumor burden is a key predictor of response to PSMA radioligand therapy.

Abstract Purpose: Two randomized clinical trials (STOMP and ORIOLE) demonstrated that stereotactic ablative radiotherapy (SABR) can prolong androgen-deprivation therapy–free survival or progression-free survival (PFS) in patients with metachronous oligometastatic castration-sensitive prostate cancer (omCSPC). Although most patients with omCSPC have a more modest delay in progression, a small subset achieves a durable response following SABR. We investigated the prognostic and predictive value of circulating prostate-specific membrane antigen-positive (PSMA+) extracellular vesicles (EV) and PSA in a biomarker correlative study using blood samples from three independent patient cohorts. Experimental Design: Plasma samples from 46 patients with omCSPC on the ORIOLE trial and 127 patients with omCSPC on the STOMP trial protocol treated with SABR were included in the study. Pre-SABR PSMA+EV levels (EV/mL) were measured by nanoscale flow cytometry. Kaplan–Meier curves and logistic regression models were used to determine the association of PSMA+EV and PSA levels with clinical outcomes. Results: In the pooled cohorts, the median biochemical PFS were 26.1 and 15.0 months (P = 0.005), and the median radiographic PFS were 36.0 and 25.0 months (P = 0.003) for PSMA+EV-low and -high groups, respectively. The combination of pre-SABR low levels of both PSMA+EV and PSA was associated with a lower risk of radiographic progression (HR, 0.34, 95% confidence interval, 0.18–0.58; P = 0.0002). In the ORIOLE cohort, which included both an SABR arm and an observation arm, low PSMA+EV was predictive of benefit from SABR (P = 0.012). Conclusions: PSMA+EV is a novel prognostic and predictive biomarker of radiographically occult tumor burden in omCSPC. PSMA+EV may inform clinical decisions about identifying patients who will achieve a durable benefit from consolidative SABR alone.

Background The American Urological Association (AUA)/Society of Urology Oncology (SUO) guidelines recommend a repeat transurethral resection of bladder tumor (TURBT) for high-risk, non-invasive (HR Ta) nonmuscle invasive bladder cancer (NMIBC) patients. The evidence base for this recommendation is weak (grade C) and fraught with methodological shortcomings, such as the lack of adjuvant intravesical Bacillus Calmette Guerin (BCG) and single-center study designs. Objective We sought to evaluate the effect of repeat TURBT on recurrence-free survival at a population level in HR Ta NMIBC patients who completed BCG induction therapy. Methods High-grade Ta NMIBC patients who underwent TURBT for a ≥5 cm tumor were identified within the SEER-Medicare database. All patients completed induction BCG and were stratified into two groups: repeat TURBT within eight weeks of initial TURBT and a group without repeat TURBT (control group). The primary endpoint was the 3-year high-risk recurrence rate. Results A cohort of 604 patients was identified, with 93 (15.4%) undergoing a repeat TURBT within eight weeks of initial TURBT and 511 (84.6%) without a repeat TURBT. Patient demographic and clinical characteristics were similar overall. No significant difference in the 3-year recurrence rate was noted (repeat TURBT: 20.4% vs. control group: 15.7%, p = 0.25). After adjusting for demographic and clinical characteristics, no association between repeat TURBT and 3-year high-risk recurrence was observed (HR (95% CI): 1.27 (0.76, 2.11); p = 0.36). Conclusion Although our study contains several major limitations, our results suggest that repeat TURBT in large volume HG Ta NMIBC treated with induction BCG therapy was not associated with improved high-risk recurrence-free survival.

Objective To define the natural history, patterns of recurrence and treatment modalities for local prostate cancer (PCa) recurrence following radical prostatectomy (RP) and radiation therapy (RT), and to investigate factors that could predict metastasis‐free survival (MFS) in this unique patient population. Methods We queried a prospectively maintained PCa registry to identify men developing in‐field recurrence (IFR) following RP and RT from 2008 to 2021 at a single institution. IFR was defined as biopsy‐proven recurrent PCa or the presence of persistent positron emission tomography‐avid lesions in the prior radiation field without evidence of metastasis. Cox regression was conducted to determine predictors of MFS. Kaplan–Meier methods were used to calculate MFS, cancer‐specific survival (CSS) and overall survival (OS) for patients in three primary therapy categories: cryoablation, androgen deprivation therapy (ADT) alone, and surveillance. Results Of 4575 patients from our registry, 108 (2.3%) with IFR were identified. The median (interquartile range [IQR]) time to IFR from salvage treatment was 78 (50–126) months. A total of 29 patients (26%) were managed with cryoablation, 23 (21%) with ADT, and 28 (25%) with surveillance. The median (IQR) follow‐up was 76 (48–100) months. There were no statistically significant differences in MFS ( P = 0.67) or OS ( P = 0.07) among the three primary treatment cohorts. Patients treated with ADT or cryoablation had longer CSS compared to patients managed with surveillance ( P = 0.047). Conclusions We found that IFR may present years after completion of primary treatment for PCa. While curative management strategies may be attempted, local and distant metastatic recurrence is common and often requires systemic therapy.