Citations

334 Background: Prostate cancer (PCa) screening has relied on prostate-specific antigen (PSA) levels to screen patients for biopsy. However, the limited specificity of serum PSA leads to high rates of negative biopsies and detection of clinically insignificant cancers. Tumor-derived extracellular vesicles, microscopic particles released by tumor cells and ubiquitously found in all bodily fluids, have emerged as novel biomarkers for a diverse set of malignancies. This study explored the utility of urine prostate-specific extracellular vesicles (ProsEVs) identified by unique surface protein markers with novel flow cytometry-based techniques as biomarkers for PCa screening. Methods: This prospective study recruited at a tertiary care center between Oct 2019 and Mar 2022. Patients with PSA≥2 ng/ml underwent prebiopsy mpMRI followed by transperineal prostate biopsy (PI-RADS 1-2) or combined MRI-guided biopsy (PI-RADS ≥ 3). Patients with metastatic PCa or prior systemic therapy were excluded. Urine samples were collected at MRI using Colli-Pee. ProsEVs were labeled using monoclonal antibodies for PSMA and STEAP1 and ProsEV concentrations were determined using nanoscale flow cytometry. EV densities were calculated by normalizing EV counts to prostate volume. Multivariable logistic regression models were constructed and model performance was compared used ROC curve analysis. Results: This study had a total of 179 patients prospectively recruited, 95 were diagnosed with Gleason score (GS) ≥ 7 prostate cancer (csPCa), while the remaining had GS <7 or benign disease. Analysis of urinary ProsEV densities revealed a significant dose-response relationship between benign, GS <7 PCa and GS ≥ 7 PCa groups and ProsEV densities (p=0.01 for PSMA, and <0.001 for STEAP1). The log sum of the PSMA and STEAP1 EV densities exhibited the strongest correlation with other ProsEV variables and was selected for model development. ROC curve analysis showed that the final model including Log Sum ProsEVs, PSA, and PI-RADS outperformed one including PSA and PI-RADS (0.733 vs 0.651, p=0.02). Specificity for detecting csPCa at a sensitivity of 90% was 39.5% in the final model compared to 37% for PSA and PI-RADS (Table). Conclusions: This study highlights the potential of urine ProsEVs as novel biomarkers for improving screening specificity for csPCa detection. Future works should explore analysis of intra-ProsEV content to further improve specificity and advance liquid biopsy techniques. [Table: see text]

320 Background: sRT is used in men with prostate cancer (PC) recurrence following radical prostatectomy (RP) signaled by a persistent or delayed elevation in PSA. It was previously reported that the use of AAT with RT improved cancer control and overall survival (OS). Long-term follow-up (FU) results are presented here. Methods: From 1998to 2003, 760 eligible post-RP patients with Stage pT3N0 or with pT2N0 and positive margins and PSA from 0.2 to 4.0 ng/mL were randomly assigned on a double-blinded, placebo-controlled trial of RT + placebo vs. RT + anti-androgen therapy (AAT) (24 months of bicalutamide, 150mg daily) during and after RT (64.8 Gy in 36 fractions prostate bed). The primary endpoint was OS estimated using Kaplan-Meier method. Time to PC death and metastatic PC (competing risk of death without an event) was estimated using cumulative incidence. The hazard ratio (HR) was obtained using Cox models (OS) and subdistribution HRs (sHRs) used the Fine-Gray model (time to PC death and metastatic PC). All tests are one-sided based on study design. Results: Median FU for surviving patients was 19 years. OS at 18 years was 53% [95% confidence interval (CI): 47-58%] for RT + AAT and 43% [95% CI: 38-48%] for RT + placebo (adjusted HR 0.82 [95% CI: 0.67-1.00], p = 0.025). The 18-year incidence of centrally reviewed PC deaths were 18% [95% CI: 14-22%] RT + AAT and 28% [95% CI: 23-32%] RT + placebo (adjusted sHR = 0.57 [95% CI: 0.42-0.78], p<0.001). The 18-year incidence of metastatic PC was 22% [95% CI: 18-26%] and 31% [95% CI: 26-35%] for AAT and placebo arms respectively with adjusted sHR = 0.59 [95% CI: 0.44-0.80, p<0.001]. Subgroup analyses is shown in the Table. Conclusions: Long term results of 24-month duration AAT during and after sRT are consistent with the primary report with significantly improved long-term OS, reduced incidence of metastatic PC and PC death for RT+AAT. Statistically significant metastatic PC was noted for Gleason score 8-10, study entry PSA>1.5 and margin positive patients and borderline significance was observed in patients with study entry PSA 0.7-1.5. Clinical trial information: NCT00002874 . [Table: see text]

314 Background: Prostate cancer patients (PC) face an elevated risk of both developing atherosclerotic cardiovascular disease (ASCVD). The American College of Cardiology Pooled Cohort Equations (PCE) for ASCVD predictions may lack accuracy. Methods: Males ≥18 years, diagnosed with PC between 2005-2012 at a hybrid academic-community practice were included. Using XGBoost algorithm we developed using a training subset of the cohort (50% train + 25% test), ranked 33 covariates (including demographic, treatment-related and social determinants of health (SDOH) information) for ASCVD prediction using SHAP (Shapley additive explanations) values. The top 10 predictors were transformed in a predictive equation using logistic regression models. This equation was tested in the cohort validation subset (25%), and subsequently compared to the PCE risk score. Results: We included 1,506 patients, with a median age of 67 (IQR 60-74) years, 13.8% had advanced stage disease (TNM III-IV), 1.5% had high risk PC (Gleason 8-10), and 20.5% received androgen deprivation therapy (ADT). Of those, 10.4% had a 10-year ASCVD risk. The PCE had an area under the curve (AUC)=0.61 and underestimated ASCVD in 0.9% (mean risk=20.1% [95% CI 17.2-23.0] vs. mean predicted risk=19.2% [95% CI 18.6-19.8]). The equation pooled from the top-10 predictors of the ML algorithm (C-index=0.78 [95% CI 0.75-0.81]) achieved an AUC=0.71 (Table). Conclusions: Conventional PCE tend to underestimate ASCVD risk in males with PC. A cancer-specific model inclusive of SDOH exhibits good performance for predicting ASCVD risk in this population. [Table: see text]

230 Background: Elevated suicide risk is established in cancer patients compared with the general population. We aim to investigate the risk of SRD among individuals diagnosed with mGU cancers. Methods: Surveillance, Epidemiology, and End Results (SEER) database (2004-2020) was queried to obtain data on suicide death in adults (>20 years of age) diagnosed with mGU cancers including bladder cancer (BC), kidney cancer (KC), and prostate cancer (PC). Standardized mortality ratios (SMRs) with 95% confidence interval (CI) were computed overall and by latency period of <1, 1-5, and >5 years (y) after the initial diagnosis of mGU cancers. SMR >1 indicated increased while <1 indicated decreased SRD. Stratification was done by age (<50y, 50-70y, >70y), race (White, Black, Asian, Native American), ethnicity (Hispanic, non-Hispanic), chemotherapy, radiotherapy, surgery, and marital. Results: This analysis included 87,357 mGU patients. In overall population, the risk of suicide-related deaths was highest <1y after diagnosis (SMR: 3.29, 95% CI: 2.47-4.29) followed by 1-5y (2.61, 2.0-3.35) and >5y (1.27, 0.61-2.34) after diagnosis. With respect to race, SRD was significantly higher in Whites (3.31, 2.46-4.36) but not in Blacks (2.58, 0.31-9.33), and Asians (2.03 (0.05-11.3). In ethnic subgroups, non-Hispanics were observed to have increased SRD (3.71, 2.77-4.86) but not Hispanics (0.83, 0.1-3.0). Patients who received chemotherapy (3.74, 2.10-6.18) or those who did not receive radiotherapy (3.66, 2.68-4.89) were more likely to die from suicide. In terms of marital status, single patients had a higher SRD (4.39, 2.94-6.30) compared to those who were married (2.54, 1.65-3.76). Detailed results are outlined in the Table. Conclusions: Patients with GU malignancies are at increased risk of SRD. Targeted and timely interventions in highest risk subgroups such as Non-Hispanic patients with a recent cancer diagnosis with no partner support, may reduce the risk of SRD in patients diagnosed with mGU cancers. [Table: see text]

229 Background: We aim to investigate non-cancer cause of death in adults within 2 years after initial diagnosis of mGU cancers including bladder cancer (BC), kidney cancer (KC), and prostate cancer (PC). Methods: Surveillance, Epidemiology, and End Results (SEER) database (2004-2020) was searched to obtain data on death caused by cardiovascular diseases (CVD), kidney diseases (KD), respiratory diseases (RD), liver diseases (LD), diabetes mellitus (DM), and sepsis in adults (>20y of age) diagnosed with mGU cancers. Standardized mortality ratios (SMRs) with 95% confidence interval (CI) were calculated within 2y of initial diagnosis. SMR was defined as the observed deaths from each category divided by the expected number of deaths in the age-matched US population for the same period. SMR >1 indicated increased while <1 indicated decreased mortality. Stratification factors included age (<50y, 50-70y, >70y), race (White, Black, Asian/Pacific Islander), ethnicity (Hispanic, non-Hispanic), chemotherapy, and radiotherapy. Results: This study including 77,246 mGU cancer patients showed that the greatest risk of early death was observed to be caused by sepsis (SMR: 4.21, 95% CI: 3.64-4.84) followed by CVD (1.70, 1.62-1.80), KD (1.58, 1.31-1.90), LD (1.58, 1.16-2.09), DM (1.56, 1.32-1.82), and RD (1.38, 1.22-1.56). Patients aged <50y observed the highest risk of mortality caused by sepsis (61.76, 30.83-110.5) followed by KD (28.06, 9.11-65.48) and CVD (5.63, 3.60- 8.84). However, patients aged 50-70y were more likely to die by RD (2.47, 1.94-3.09) and LD (2.01, 1.38-2.82). The results were consistent for Black patients; sepsis (6.59, 5.04-8.46) followed by RD (2.01, 1.41-2.78) and KD (1.64, 1.04-2.46). Asian/Pacific Islanders were more likely to die from CVD (2.52, 2.13- 3.00) and DM (2.21, 1.21-3.71). Hispanics were more likely to die from LD (3.11, 1.66-5.32) and non-Hispanics from sepsis (4.28, 3.68-4.96). This risk of death due to sepsis was increased with chemotherapy (7.06, 5.22-9.33) and radiotherapy (4.92, 3.58-6.61). Detailed results are available in Table. Conclusions: Sepsis remained the leading cause of early non-cancer-deaths in mGU cancers consistently across all subgroups. Younger adults were more likely to die from CVD and KD, Black patients from RD, and Hispanics from LD. [Table: see text]

220 Background: There is a critical need to identify biomarkers of response and resistance to 177Lu-PSMA-617. Post-hoc analyses of VISION have explored the prognostic and predictive value of select clinical parameters. However, we are still in the early stages of deciphering which molecular changes are associated with favorable or adverse treatment outcomes. Methods: We conducted a retrospective analysis of patients with metastatic castration-resistant prostate cancer (mCRPC), who received 177Lu-PSMA-617 at Mayo Clinic in Rochester, Minnesota, in the interval of March 2022 to March 2023. We included patients who provided research authorization, had a baseline PSA of at least 2 ng/mL, received at least 2 cycles of treatment, and had circulating tumor DNA (ctDNA) genomic profiling performed by Guardant (83 gene panel) within 60 days of treatment initiation. Clinical, laboratory, genomic, and radiomic parameters were abstracted by trained research personnel. Two independent analyses of “response” and “resistance” were performed. Response to treatment was defined as 50% or greater decrease in PSA from baseline (PSA50 response: dichotomized yes versus no), and resistance was defined as non-decreasing or rising PSA during treatment (PSA non-response: dichotomized yes versus no). Associations between gene alterations and response and resistance were evaluated via Fisher’s exact tests. Results: Between March 2022 and March 2023, 273 patients received cycle 1 of 177Lu-PSMA-617. A total of 108 patients met the inclusion criteria. The median number of cycles at data cutoff was 6 (IQR: 4,6) with 57 (53%) patients receiving all 6 planned cycles. The median PSA at baseline was 16.65 ng/ml (IQR: 5.20, 66.12). A total of 65 patients (60%) experienced a PSA50 response. No molecular alterations were associated with a higher rate of PSA50 response; however, alterations in ARID1A, AR, and CHEK2 were associated with lack of PSA50 response (Fisher’s exact p < 0.05). Of the 108 evaluable patients, 20 (19%) met criteria for PSA non-response. Alterations in AR, ARID1A, MYC, TP53, CHEK2, ATM, EGFR, and NOTCH1 were significantly associated with PSA non-response (Fisher’s exact p < 0.05); in each case, the presence of the alteration was positively associated with resistance (i.e., more instance of PSA non-response). No biomarkers were found to be inversely associated with PSA non-response. Conclusions: ctDNA assessed by commercially available, targeted sequencing panels prior to treatment may be useful in identifying the patients least likely to benefit from 177Lu-PSMA-617. Further work is ongoing to integrate ctDNA findings with clinical parameters in the hopes of understanding the factors mediating response and resistance to therapy.

216 Background: PCa harbors recurrent FOXA1 alterations, yet distinct alteration types may drive divergent consequences. Here, we established several classes of FOXA1 alterations and evaluated their clinical outcomes, molecular correlates, and immunologic landscape in a large cohort of primary and metastatic PCa samples from Caris Life Sciences. Methods: We interrogated the Caris DNA (592-gene/whole exome) and RNA (whole transcriptome) NGS databases. FOXA1 alterations were annotated based on amino acid (a.a.) location and prior functional studies (Table). Real-world overall survival (OS) was determined from insurance claims data using Kaplan-Meier estimates. Gene set enrichment analyses (GSEA) was used to estimate signaling pathway activity. Immune-cell fractions were inferred from bulk RNA-seq using quanTIseq. All comparisons are made relative to FOXA1 WT cases. Results: The overall prevalence of FOXA1 alterations was 16%, with no enrichment in metastatic PCa samples (15.5%). Class 2 mutations were enriched in histologic NEPC, were associated with a classical NEPC mRNA signature, and showed poor survival with ADT (HR 5.6, 95% CI: 2.5–12.5, p<0.001). Conversely, metastatic PCa patients with Class 1B mutations had numerically improved survival with ADT (HR 0.76, 95% CI: 0.50–1.14, p=0.18). All FOXA1 alterations (except Class 2) resulted in increased FOXA1 transcripts, with 1B and 1C having the greatest effects (q<0.0001). Class 0 and 3 alterations had 2–5 fold higher frequency of TMB-high and MSI-high status (q<0.05). Conversely, Class 1B exhibited lower TMB and markedly fewer TP53 mutations (35.7% vs 20.3%, q<0.001) and TMPRSS2-ERG fusions (34.5% vs 4.6%, q<0.001). Class 1B was depleted of AR transcriptional signatures (q=0.01) but enriched of MYC signaling in GSEA analysis (FDR<0.001), and showed reduced expression of B7-H3. On immune-cell deconvolution analysis, Class 1B showed reduced dendritic cells, but increased B cells and neutrophils (DC: 1.96% vs 0.01%, B cell: 4.27% vs 5.29%, neutrophils: 5.05% vs 8.00%, each q<0.001). Conclusions: Different FOXA1 alterations exhibit divergent molecular and clinical features, and should not be interpreted in aggregate. In particular, Class 1B mutations are associated with a unique molecular and immunological landscape with potentially better outcomes to ADT, while Class 2 mutations are associated with NEPC phenotype with inferior ADT sensitivity. [Table: see text]

212 Background: Patients with prostate cancer with liver metastases are known to have a worse prognosis. In this study, we evaluated ctDNA in mCRPC (metastatic castration-resistant prostate cancer) patients with and without liver metastases. Methods: A retrospective chart review identified mCRPC patients with liver metastases at Tulane Cancer Center and Huntsman Cancer Institute. Liver metastases were confirmed via molecular or conventional imaging. All patients had ctDNA assessed with a multi-gene cancer panel via the Guardant 360 assay. Alterations with <0.1% allelic fraction, synonymous alterations, and variants of unknown significance were excluded from analyses. Statistical analyses were performed using Fisher’s Exact and Wilcoxon Rank Sum Tests. Correction for multiple testing was not performed, hence these alterations may be subject to a type 1 error. Results: 53 mCRPC patients with liver metastases and 144 mCRPC patients without liver metastases were included in the study. We found seven genes that are more likely to be pathologically altered in ctDNA in mCRPC patients with liver metastases (See Tables 1-3): AR (OR=2.38, 95% CI: [1.25, 4.52], p=0.01), BRAF (OR=2.74, 95% CI:[1.05, 7.18], p=0.05), BRCA2 (OR=5.33, 95% CI:[1.49, 19.02], p=0.01), CDK6 (OR=4.09, 95% CI:[1.35, 12.42], p=0.01), EGFR (OR=3.12, 95% CI:[1.22, 7.99], p=0.02), FGFR1 (OR=5.69, 95% CI:[1.81, 17.86], p-value=0.003), MYC (OR=4.55, 95% CI:[1.63, 12.68], p=0.004), and PIK3CA (OR=4.34, 95% CI:[1.87, 10.06], p=0.01). Additionally, mCRPC patients with liver metastases are more likely to have copy number alterations (CNA) (p= 0.01) compared to mCRPC patients without liver involvement. There were no other significant differences in the remaining 70 genes interrogated. Germline pathogenic alterations did not vary between the two groups. Conclusions: In mCRPC patients with liver metastases, these exploratory analyses suggest ctDNA testing is more likely to detect pathologic alterations in AR, BRAF, BRCA2, CDK6, EGFR, FGFR1, MYC, and PIK3CA. Additionally, mCRPC patients were more likely to have copy number alterations (CNA). Limitations of the Guardant 360 assays are notable in this setting given the incomplete ascertainment of gene deletions and the incomplete number of prostate-relevant genes assessed. [Table: see text]

191 Background: Two randomized clinical trials have demonstrated that SABR can prolong time to progression in oligometastatic castration-sensitive prostate cancer (omCSPC) patients. However, there is a need for predictive tools to identify patients who will benefit from SABR alone or with systemic therapy. We investigated the prognostic value of PSMA-positive extracellular vesicles (PSMA+EVs) in a blinded observational study using blood samples from three independent patient cohorts. Methods: We obtained plasma samples from 157 omCSPC patients treated with SABR from the ORIOLE cohort (N=30, JHU) and STOMP-like cohorts (N=80, UGhent; N=47, Iridium Net). Baseline PSMA+EV levels (EV/ml) were measured by nanoscale flow cytometry. Primary clinical endpoints were biochemical progression (bPFS) and radiographic progression (rPFS). Optimal cutoffs for PSA (ng/ml) and PSMA+EV (EVs/ml) were defined as the point with the most significant log-rank test split. Kaplan-Meier curves and univariate Cox regression models were used to determine the association of PSMA+EV levels with clinical outcomes. Results: Twenty percent of patients (N=157 total) were diagnosed with bone scan, 79% with PET imaging, and 1% with other modalities. Ninety-four percent of patients presented with ≤3 metastases on imaging. In the pooled STOMP-like cohorts, median bPFS was 27.9 and 18.0 months for PSMA+EV low and high groups, respectively (p=0.039). Median rPFS was 36.0 versus 27.0 months (p=0.029). In the ORIOLE cohort, median bPFS was 24.3 and 5.9 months in PSMA+EV low and high, respectively (p=0.021). Median rPFS was 36.0 versus 11.1 months (p=0.019). High baseline PSMA+EV levels were associated with higher risk of both biochemical and radiographic progression (Table). Combination of baseline PSA low and PSMA+EV low outperformed either biomarker alone and better predicted risk of disease progression after SABR. Conclusions: While prospective biomarker-guided trials are warranted, a PSMA+EV blood test can aid patient selection by identifying omCSPC patients who may have durable responses to SABR without ADT. [Table: see text]

175 Background: It is well-known that patients with liver metastases from metastatic castration resistant prostate cancer (mCRPC) have poorer or transient responses to many forms of systemic therapy. Data on outcomes following treatment with Lutetium-177–PSMA-617 is scarce. The VISION trial reports hazard ratios for overall survival in the subgroup of patients with liver metastases without disclosing the absolute duration of survival. Using real-world clinical data, we examine this important subgroup of patients, describing their PSA response rates and survival. Methods: A single institution database was assembled to include all patients receiving 177-Lu-PSMA-617 at Mayo Clinic Rochester, MN, and starting treatment in the interval of March 2022 to March 2023. Baseline clinicopathologic and imaging characteristics were abstracted. Patients were categorized based on the presence or absence of measurable liver metastases on their baseline PSMA PET scan. Best PSA response while on treatment was annotated and reported as percent decline from baseline. Survival was calculated from date of first cycle of 177-Lu-PSMA-617. PSA50 response and overall survival (OS) outcomes for the two groups (liver metastases versus no liver metastases) were compared using Chi square test and Kaplan-Meier method, respectively. Those with available pre-treatment circulating tumor DNA (ctDNA) genomic profiling, performed by Guardant (83 gene panel), were assessed for the presence of pathogenic and likely pathogenic alterations. Findings are summarized using descriptive statistics. Results: The overall cohort consisted of 212 patients, including 29 (14%) with liver metastases on pre-treatment PSMA PET/CT. The median number of cycles received was 4 (range, 1-6) for patients with liver metastases and 6 (range, 1-6) for those without hepatic involvement. The observed PSA50 response trended lower for those with liver metastases (34.5% [10/29] versus 51% [94/183], p= 0.091). At median (IQR) follow-up of 10 (8-12) months, there was a numerical but not statistically significant difference in median OS (11.28 months versus NR, p=0.066). In the exploratory analysis of baseline ctDNA, BRCA2 copy number loss was relatively enriched among patients with liver metastases (4 of 19, 21%) versus patients without liver disease (5.7%, 9/158). Conclusions: Our data suggest that the presence of liver metastases predict poorer outcomes in patients receiving Lutetium-177–PSMA-617 treatment, which is similar to data reported with other forms of systemic therapy for mCRPC. To maximize the anti-tumor activity of radioligand therapy in the liver, combination approaches should be explored.