Final phase III PROSPER trial data of Xtandi shows benefits in non-metastatic castration-resistant prostate cancer.- Pfizer and Astellas

Pfizer and Astellas have announced final results from the overall survival (OS) analysis of the Phase III PROSPER trial, which evaluated Xtandi (enzalutamide) plus androgen deprivation therapy (ADT) versus placebo plus ADT in men with non-metastatic castration-resistant prostate cancer (nmCRPC). In the trial, Xtandi plus ADT reduced the risk of death by 27% (n=1,401; hazard ratio [HR]=0.73; [95% confidence interval [CI]: 0.61-0.89]; p=0.001) compared to placebo plus ADT. The median OS was 67.0 months (95% CI: 64.0 to not reached) for men who received Xtandi plus ADT compared to 56.3 months (95% CI: 54.4 to 63.0) with placebo plus ADT. OS was a key secondary endpoint of the trial. These data were simultaneously published online in the New England Journal of Medicine and presented during the virtual scientific program of the 2020 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract #5515). In findings published in the New England Journal of Medicine in 2018, the PROSPER trial met its primary endpoint of metastasis-free survival (MFS), demonstrating a significant reduction in the risk of developing metastasis or death with Xtandi plus ADT compared to ADT alone in men with nmCRPC (HR=0.29 [95% CI: 0.24-0.35]; p<0.001). mfs was measured as the time from patients entering the trial until their cancer was radiographically detected as having metastasized or until death within 112 days of treatment discontinuation. the safety profile observed in the final os analysis was consistent with the 2018 primary analysis and the established safety profile of enzalutamide.see: enzalutamide in men with nonmetastatic castration-resistant prostate cancer. maha hussain et al. n engl j med 2018 378:2465-2474 doi: 10.1056 nejmoa1800536>