Retrospective cohort analysis of real-world clinical outcomes in nonmetastatic (M0) castration-resistant prostate cancer (CRPC) treated with novel androgen receptor pathway inhibitors (ARPI).

Abstract

51 Background: The landscape of M0 CRPC has changed with the recent demonstration of metastasis-free survival (MFS) and overall survival (OS) improvements with the use of ARPIs in clinical trial settings. However, the extrapolation of this data to clinical practice is limited by strict exclusion criteria in these trials, including prior or concurrent malignancy, cardiovascular disease, or hypertension. The purpose of this study was to assess real-world outcomes in patients with M0 CRPC treated with ARPIs compared to historical controls. Methods: We designed a retrospective cohort study with the inclusion of patients in Alberta, Canada diagnosed with M0 CRPC between 2001-2020. Via chart review, we identified baseline characteristics, potential confounders, treatment details, and clinical outcomes. The primary outcome of interest was MFS. Secondary outcomes included: second progression-free survival (PFS2) and OS. Median survival times were measured using the Kaplan-Meier method and the log-rank test was used for comparison of outcomes based on ARPI exposure. Cox proportional hazard regression models were used to calculate hazard ratios (HR) accounting for impact of PSA doubling time (PSADT), use of osteoclast inhibiting agents, and presence of pelvic lymphadenopathy. Results: We identified 211 patients across multiple centres in Alberta with M0 CRPC, with 54 having received apalutamide (40/54), enzalutamide (7/54), or darolutamide (7/54). Median age at M0 CRPC diagnosis was 74 years; median PSADT was 4.4 months; and 19% of patients (40/211) had pelvic lymphadenopathy at diagnosis. Median MFS in patients treated with ARPIs was 47.5 months compared to 20.6 months in those not treated with ARPIs (HR, 0.23; 95% confidence interval [CI], 0.11-0.49; p < 0.001). Median PFS2 in ARPI treated patients was 66.3 months compared with 35.6 months (HR, 0.40; 95% CI, 0.18-0.87; p = 0.022). Median OS for patients treated with ARPI was not reached. Conclusions: Given the older age of men with advanced prostate cancer, real-world outcomes that include patients with comorbidities are important adjuncts to the interpretation of clinical trials exploring the benefit of novel therapeutics. Here, we demonstrate that in a real-world, unselected population of men with M0 CRPC, apalutamide, enzalutamide, and darolutamide seem to confer similar MFS and PFS2 benefits to those demonstrated in the SPARTAN, PROSPER, and ARAMIS studies. Real-world OS data remain immature and will be an important addition to these findings.