Metastasis free survival in older men with nonmetastatic castration-resistant prostate cancer treated with androgen receptor inhibitors: An FDA-pooled analysis.

Abstract

12038 Background: The FDA has approved three androgen receptor (AR) inhibitors for nonmetastatic castration-resistant prostate cancer (nmCRPC) based on improvements in metastasis-free survival (MFS). MFS is an earlier endpoint, defined as the time from randomization to either imaging-detectable distant disease or death. This pooled analysis examines MFS, time to initiation of cytotoxic chemotherapy (TTCyto), and safety outcomes in men over 80 treated with AR inhibitors. Methods: Data was pooled from three randomized controlled studies (n=4117) of AR inhibitors for nmCRPC. The treatment effect of AR inhibitors on MFS and TTCyto across age groups was evaluated using Kaplan-Meier estimates and a Cox proportional hazards regression model. Hazard Ratios for MFS and TTCyto were adjusted for baseline ECOG, total Gleason score, PSA doubling time, and prior bone-targeting therapy. Results: For patients age 80 years or older (n=675) who were treated with AR inhibitors, the hazard ratio was 0.38 (95% CI 0.29, 0.49) with an estimated median MFS of 40 months (95% CI 36, 41) versus 22 months (95% CI 18, 29) for those treated with placebo (n=348). For patients <80 (n=2019) treated with AR inhibitors, the HR was 0.31 (95% CI 0.27, 0.36) with an estimated median MFS of 41 months (95% CI 36, NR) versus 16 months (95% CI 15, 18) for those treated with placebo (n=1075). Patients over 80 also derived similar improvements in time to initiation of cytotoxic chemotherapy (HR 0.43 95% CI 0.23, 0.82), compared to their younger counterparts (HR 0.41 95% CI 0.33, 0.50). See Table for selected safety outcomes. Conclusions: In an exploratory subgroup analysis, older men (≥80) with nmCRPC derived similar benefit in MFS and time to initiation of cytotoxic chemotherapy with AR inhibitors compared with younger patients. Men age 80 and above experienced higher rates of Grade 3-4 adverse events, serious adverse events, falls, and fractures. This trend towards increased toxicity was observed regardless of treatment arm. Analysis of patient reported outcomes is ongoing. [Table: see text]