Effect of crossover from placebo to darolutamide on overall survival in men with non-metastatic prostate cancer: sensitivity analyses from the randomised phase 3 ARAMIS study

Abstract

BackgroundIn the phase 3 ARAMIS study (NCT02200614), darolutamide significantly improved metastasis-free survival in patients with non-metastatic castration-resistant prostate cancer (nmCRPC). Following the primary analysis, the study was unblinded, and placebo recipients were permitted to cross over to open-label darolutamide. Despite crossover, darolutamide significantly improved overall survival (OS). We conducted sensitivity analyses to estimate the effect of placebo–darolutamide crossover on OS. MethodsPatients with nmCRPC were randomised to oral darolutamide 600 mg twice daily (n = 955) or placebo (n = 554). Prespecified (rank-preserving structural failure time [RPSFT] and iterative parameter estimation [IPE]) and post hoc (OS-adjusted censoring and inverse probability of censoring weighting [IPCW], with weightings for baseline testosterone and prostate-specific antigen) sensitivity analyses were conducted. ResultsAfter unblinding, 170 of 554 placebo recipients (30.7%) crossed over to darolutamide. At the final OS intention-to-treat analysis (median 11.2 months after unblinding), darolutamide significantly improved OS by 31% versus placebo (hazard ratio [HR] 0.69, 95% confidence interval [CI] 0.53–0.88; P = 0.003). The benefit increased in the analyses adjusting for crossover is as follows: RPSFT HR 0.68, 95% CI 0.51–0.90; P = 0.007; IPE HR 0.66, 95% CI 0.51–0.84; P < 0.001; OS-adjusted censoring HR 0.59, 95% CI 0.45–0.76; IPCW HR 0.63, 95% CI 0.48–0.81. The favourable safety profile of darolutamide was maintained, including in crossover patients. ConclusionsAfter adjusting for crossover, darolutamide reduced the risk of death by up to 41% in patients with nmCRPC. The effect of darolutamide on OS may have been underestimated in the original intention-to-treat analysis.