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

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