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132 Background: Distant metastasis at the time of prostate cancer (PCa) diagnosis is associated with increased morbidity and mortality. This study aimed to assess the impact of sociodemographic characteristics on distant metastasis at the time of PCa diagnosis. Methods: The Surveillance Epidemiology and End Results (SEER) database (2000-2021), including PCa patients from 17 registries, was queried. Patients with late-stage diagnosis (LSD) were defined as those who were initially diagnosed with stage IV disease, indicating distant metastasis. Sociodemographic predictors included race, ethnicity, age, marital status, residential status, and median household income. Multicollinearity was assessed using variance inflation factors (VIF). Univariable logistic regression was performed to identify significant predictors of LSD, which were further analyzed in multivariable logistic regression using a maximum likelihood estimation approach. Odds ratios with 95% confidence intervals (CI) were computed with a p-value of <0.05 indicating a statistically significant association. Results: Of the 1,089,736 PCa patients diagnosed, 64,983 (6%) had an LSD. The majority were white (80%), non-Hispanic/Latino (HL) (91%), aged ≥65 years (60%), married (75%), residents in metropolitan areas (88%), and had an annual house income of ≥$70,000 (70%). Multivariable logistic regression identified Black (OR: 1.24; 95%CI: 1.22-1.27), Asian or Pacific Islander (1.35; 1.30-1.40), and American Indian/Alaska Native (1.70; 1.53-1.89) to have higher odds of LSD compared to White patients (Table). In addition, HL ethnicity compared to non-HL (OR: 1.45; 95% CI: 1.42-1.49), age ≥65 compared to <65 (1.68; 1.65-1.71), unmarried status compared to married (1.88; 1.85-1.91), residency in non-metropolitan areas compared to metropolitan (1.10; 1.07-1.12), and household income <$70,000 compared to ≥$70,000 (1.03; 1.01-1.05) had a significant association with LSD. Conclusions: Older, non-White (Black, Asian/Pacific Islander, American Indian/Alaska Native), Hispanic/Latino, unmarried men, residents of non-metropolitan areas, or those with lower annual household incomes have higher odds of late-stage diagnosis. Interventions targeting early detection in these at-risk groups may improve prostate cancer outcomes in the US. Variable Odds Ratio (95% CI) p-value Race (Black vs White) 1.24 (1.22-1.27) <0.01 Race (Asian or Pacific Islander vs White) 1.35 (1.31-1.40) <0.01 Race (American Indian/Alaska Native vs White) 1.70 (1.53-1.89) <0.01 Ethnicity (Hispanic/Latino vs non-/Hispanic/Latino) 1.45 (1.42-1.49) <0.01 Age (≥65 vs <65) 1.68 (1.65-1.71) <0.01 Marital status (unmarried vs married) 1.88 (1.85-1.91) <0.01 Residence status (non-metropolitan vs metropolitan) 1.10 (1.07-1.12) <0.01 Household income (<$70,000 vs ≥$70,000) 1.03 (1.01-1.05) <0.01

129 Background: Few studies have explored the use of focal therapies to address select sites of resistant disease in men receiving 177-Lu-PSMA-617 for metastatic castrate resistant prostate cancer (mCRPC). Our institutional practice is to offer SBRT for patients with up to 5 sites of oligoprogression or non-responding lesions while undergoing 177Lu-PSMA-617 (every 6 weeks for 6 cycles total). This is determined by PSMA or choline PET imaging during the course of 177Lu-PSMA-617. Herein, we evaluated the safety of adding target SBRT during treatment with 177Lu-PSMA-617. Methods: This retrospective single institution analysis was conducted via systematic chart review to evaluate for adverse events during or after treatment. Grading of treatment-related adverse events was conducted using Common Terminology Criteria for Adverse Events Version 5.0 (CTCAE v5). Results: Thirty-one patients receiving 177Lu-PSMA-617 with 51 sites of oligoprogressive or non-responding metastatic disease were treated with SBRT. The median number of sites treated was 1 (range 1-4). Most patients received SBRT immediately after cycle 6 (32%) or after cycle 3 or 4 (42%). Bone was the most commonly treated site of disease (90%) with the majority (54%) of bone sites being spine or sacrum, followed by lymph nodes (10%). Ultimately, 84% of patients completed all 6 cycles of 177Lu-PSMA-617 (range 4-6). The median follow-up time was 19.1 months (IQR 15.5-22.4) after 177Lu-PSMA-617 therapy start. A total of 2 patients experienced a pathologic fracture within the SBRT treatment field that could possibly be related to radiotherapy. One patient experienced a grade 2 neuropathy which may have been related to radiation therapy. Other potential adverse events are listed (Table). Conclusions: Our data demonstrates a low rate of significant toxicity with the use SBRT during treatment with 177Lu-PSMA-617. Further study is indicated to determine the oncologic efficacy and potential late side effects of this treatment strategy. Adverse events. Event All Grades Grade > 3 Any Adverse Event 104 2 Anemia 29 (94%) 0 Low Platelets 11 (35.5%) 1 (3.2%) Any Pathologic Fracture 7 (22.5%) 1 (3.2%) Possible SBRT-related Pathologic Fracture 2 (6.5%) 1 (3.2%) Bone Pain Flare 3 (9.6%) 0 Neuropathy 1 (3.2%) 0

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.

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.

Abstract Purpose: Around 10% to 15% of prostate cancers harbor recurrent aberrations in the Forkhead Box A1 gene, FOXA1, whereby the alteration type and the effect on the forkhead (FKH) domain affect protein function. We developed a FOXA1 classification system to inform clinical management. Experimental Design: A total of 5,014 prostate cancer samples were examined using whole-exome and -transcriptome sequencing from the Caris Life Sciences database. We denoted class 1 FOXA1 alterations as missense and in-frame insertions/deletions with subclasses oriented with respect to the FKH domain. These were in the first part of the FKH domain [class 1A: amino acids (AA) 168–246], within the Wing2 region of FKH (class 1B: AA 247–269), or outside FKH (class 1C: AA 1–167, 270+). Two hotspot missense mutations at R219 were denoted class 2. Class 3 included predicted truncating mutations with subclasses partitioned based on the FKH domain (class 3A: AA 1–269 and class 3B: AA 270+). Class 4 represented FOXA1 amplifications. Real-world overall survival and therapy outcomes were determined from insurance claims. Results: FOXA1 alterations did not influence survival when considered in aggregate but had distinct prognostic effects when stratified by class. In primary prostate samples, class 1A alterations were associated with overall improved survival (HR, 0.57; P = 0.03); a similar trend was seen in metastatic biopsies with class 1B (HR, 0.84; P = 0.09). Conversely, in primary specimens, class 1C exhibited worse survival upon second-generation androgen receptor signaling inhibitor treatment (HR, 1.93; P &lt; 0.001). Class 2 mutations (R219C/S) were enriched in neuroendocrine prostate cancers and were associated with overall poor survival (HR, 2.05; P &lt; 0.001) and worse outcomes to first-line androgen-deprivation therapies (HR, 2.5; P &lt; 0.001). Class 3A alterations indicated improved survival (HR, 0.70; P = 0.01), whereas class 3B alterations portended poor outcomes (HR, 1.50; P &lt; 0.001). Amplifications (class 4) indicated poor outcomes in metastatic samples (HR, 1.48; P = 0.02). Molecularly, different FOXA1 alteration classes harbored distinct mutational and immunologic features as well as unique transcriptional programs. Finally, relative to European Americans, African Americans had increased class 1C alterations, whereas Asian/Pacific Islander patients had increased class 1B alterations. Conclusions: FOXA1 alterations should not be interpreted in aggregate, as different classes are associated with divergent molecular features and clinical outcomes. Our revised classification schema facilitates clinical decision-making for patients with prostate cancer and uncovers important racial differences.

Abstract Introduction: Immune checkpoint inhibitors (ICI) are an essential systemic therapy for advanced melanoma. However, most melanomas develop resistance to ICI. Tumor-derived soluble PD-L1 (sPD-L1) and other soluble immunosuppressive factors drive checkpoint inhibitor resistance and correlate with inferior survival. We previously showed that therapeutic plasma exchange (TPE) removes sPD-L1 from circulation. Thus, we hypothesized that TPE-mediated removal of sPD-L1 and other immunosuppressive factors could overcome immunotherapy resistance in refractory melanoma. Methods: In this clinical trial (NCT04581382), we prospectively enrolled eighteen (18) patients with widely metastatic melanoma with progression despite anti-PD-1 ICI and elevated sPD-L1 by ELISA (≥1.7ng/mL). Each patient received radiotherapy to between one and three metastatic lesions (at least two unirradiated lesions) followed by three TPE sessions on consecutive days and re-challenge with checkpoint inhibitor. The primary safety and efficacy endpoints of the study were adverse events (AEs) and sPD-L1 reduction by TPE, respectively. Secondary endpoints included RECIST-based response in unirradiated lesions and overall survival. Correlative studies included kinetics of sPD-L1 and soluble immonsuppressive factors and dynamics of peripheral immune cell phenotypes. Results: Mean age was 62 (SD 13) and seven of eighteen (39%) were female. Mean baseline sPD-L1 was 26.31 ng/mL (40.01). The treatment was well-tolerated with one (6%) patient with grade 3 and 4 adverse events from a central line infection after TPE. Levels of sPD-L1 were significantly reduced by TPE (mean 80.2% reduction, p<0.0001). Two patients (11.1%) experienced complete response (CR), one (5.6%) partial response, three (16.7%) stable disease, and 12 (66.7%) progressive disease. In one case, immunotherapy was discontinued after two years due to no detectable lesions. Changes in tumor-reactive (TTR) GZMB+/CX3CR1+/CD11ahigh and other peripheral immune cell populations predicted overall survival in this cohort. In addition to sPD-L1, other soluble mediators of ICI resistance were also reduced by TPE and predicted overall survival in this cohort. Summary/Conclusion: sPD-L1 and other soluble immunoregulatory signaling molecules are important mediators of ICI resistance. SBRT and TPE can resensitize ICI-refractory melanoma by removing these factors. Patients with persistently elevated or rapid rebound of sPD-L1 following TPE experienced poor response and overall survival. Serial monitoring of sPD-L1 may predict response to ICI and multiple courses of TPE may be necessary. Our findings may apply in other ICI-resistant cancers with elevated sPD-L1. ClinicalTrials.gov registration: NCT04581382, ReCIPE-M1 (Rescuing Cancer Immunotherapy with Plasma Exchange in Melanoma 1).

Abstract Purpose: Metastatic castration-resistant prostate cancer (mCRPC) resistant to androgen receptor signaling inhibitors (ARSI) is often lethal. Liquid biopsy biomarkers for this deadly form of disease remain under investigation, and underpinning mechanisms remain ill-understood. Experimental Design: We applied targeted cell-free DNA (cfDNA) sequencing to 126 patients with mCRPC from three academic cancer centers and separately performed genome-wide cfDNA methylation sequencing on 43 plasma samples collected prior to the initiation of first-line ARSI treatment. To analyze the genome-wide sequencing data, we performed nucleosome positioning and differential methylated region analysis. We additionally analyzed single-cell and bulk RNA sequencing data from 14 and 80 patients with mCRPC, respectively, to develop and validate a stem-like signature, which we inferred from cfDNA. Results: Targeted cfDNA sequencing detected AR/enhancer alterations prior to first-line ARSIs that correlated with significantly worse progression-free survival (P = 0.01; HR = 2.12) and overall survival (P = 0.02; HR = 2.48). Plasma methylome analysis revealed that AR/enhancer lethal mCRPC patients have significantly higher promoter-level hypomethylation than AR/enhancer wild-type mCRPC patients (P &lt; 0.0001). Moreover, gene ontology and CytoTRACE analysis of nucleosomally more accessible transcription factors in cfDNA revealed enrichment for stemness-associated transcription factors in patients with lethal mCRPC. The resulting stemness signature was then validated in a completely held-out cohort of 80 patients with mCRPC profiled by tumor RNA sequencing. Conclusions: We analyzed a total of 220 patients with mCRPC, validated the importance of cell-free AR/enhancer alterations as a prognostic biomarker in lethal mCRPC, and showed that the underlying mechanism for lethality involves reprogramming developmental states toward increased stemness. See related commentary by Nawfal et al., p. 7

3020 Background: Radioligand therapy (RLT) use has been increasing with the approval of 177Lu-Dotatate for metastatic neuroendocrine tumors (NET) & 177Lu-PSMA-617 for metastatic castration resistant prostate cancer (mCRPC). Therapy-related myeloid neoplasms [tMN, including myelodysplastic syndrome (MDS) & acute myeloid leukemia, (AML)] have been reported after 177Lutetium (177Lu) for NET with rates of 2-20% & median time from first 177Lu to tMN of 2.8yrs [4-12]. Clonal hematopoiesis (CH) is a risk factor for tMN, with the spectrum of CH depending on selection pressures. To describe the prevalence of therapy selected CH & tMN, we performed a retrospective analysis of patients (pts) who had a bone marrow biopsy (BMB) post-177Lu. Methods: After IRB approval, we queried the electronic health record for pts with BMB post-177Lu. Pt demographics, treatment history, labs & BMB results were collected. Results: Fifty-seven pts met criteria, 41 (72%) with NET & 16 (28%) with mCRPC. . Median age at BMB was 68yrs (range, 28-85). Of the 57pts, prior treatments included: radiation (RT) in 21 (37%), temozolomide in 14 (25%), taxane in 15 (26%), & platinum agents in 10 (18%). The median number of 177Lu cycles was 4 (range, 1-11).Cytogenetics were available in 84% (n = 48) & were normal in 60% (n = 29). Of those with abnormal cytogenetics (n = 18, 38%), the most common abnormalities involved chromosome (chr) 7 (n = 12, 26%), chr 5 (n = 7, 15%), chr 20 (n = 5, 11%) and complex karyotypes in 7 (15%), with 3 (17%) of these patients having no mutations. Diagnoses were assessable in 49 (86%) pts: 15 (31%) with undefined cytopeniasand 16 (33%) with tMDS. Metastatic carcinoma was identified in 17 Fifty-one percent (n = 29), at a median of 0.5yrs (range, 0.04-2.6) after hematologic diagnosis. Conclusions: The enrichment of CH involving the DDR pathway in recipients of 177Lu underscores the impact of RLT on bone marrow progenitors.

12079 Background: Many troublesome symptoms experienced by men with prostate cancer are not specific to a particular disease state or treatment modality. As such, these issues' scope is neither fully appreciated nor characterized in the reporting of clinical trial data. A modern accounting of poorly controlled symptoms is needed to better inform survivorship and supportive care efforts. Methods: Data are drawn from the Enhanced, EHR-facilitated Cancer Symptom Control (E2C2) study, a cluster-randomized stepped wedge trial examining the effectiveness of routine symptom assessment and management on patient-centered outcomes and healthcare utilization (NCT03892967). This is a population-level study supporting patients with cancer, who are cared for in medical oncology clinics across the Midwest United States. The trial utilizes an automated symptom monitoring system with EHR-enabled algorithms for symptom triage and intervention. The current analysis focuses on pre-intervention surveys. The cohort includes E2C2 participants with prostate cancer (as determined by the Mayo Clinic Cancer Registry) receiving curative or palliative-intent therapies, along with prostate cancer survivors who previously completed their treatment. The prevalence of SPPADE symptoms (sleep disturbance, pain, impaired physical function, anxiety, depression, fatigue [low energy]) was assessed using 0 to 10 numerical rating scales (NRS), with scores of 4-6 indicating moderate symptoms and 7-10 indicating severe symptoms. Results: A total of 1,388 men with prostate cancer completed a pre-intervention survey between March 2019 and January 2023. The median age at completion of first survey was 74 years. The cohort includes patients living in diverse settings, including urban (n=718, 52%), micropolitan (n=250, 18%), small town (n=218, 16%), and rural (n=200, 14%) environments. The proportion of patients experiencing moderate-to-severe symptoms (NRS score ≥4) was 47% for fatigue, 40% for impaired physical function, 32% for sleep disturbance, 27% for pain, 22% for anxiety, and 20% for depression/emotional distress. The three domains with the highest prevalence of severe symptoms (NRS score ≥7) were fatigue (17%), impaired physical function (12%), and sleep disturbance (10%). Conclusions: Proactive symptom monitoring identifies a high overall burden of moderate-to-severe symptoms, particularly fatigue and impaired physical function, among prostate cancer patients and survivors. Collaborative care approaches and symptom control trials are needed to mitigate and manage these burdensome symptoms. Clinical trial information: NCT03892967 . [Table: see text]