Efficacy of androgen receptor antagonists in combination with androgen deprivation therapy in nonmetastatic, castration-resistant prostate cancer: A systematic review and meta-analysis of published phase III randomized controlled trials.

Abstract

e17606 Background: Nonmetastatic, castration-resistant prostate cancer (nmCRPC) often heralds metastatic disease which is responsible for majority of the morbidity and mortality associated with prostate cancer. Hence, delaying metastasis is an expedient therapeutic goal for the patients with nmCRPC. Three androgen receptor (AR) antagonists — apalutamide, enzalutamide, and darolutamide — have been approved recently for nmCRPC on the basis of prolongation of metastasis-free survival. The purpose of our meta-analysis is to consolidate the efficacy data of AR-antagonists prolonging metastasis-free survival in nmCRPC. Methods: We conducted a systematic search at PUBMED, MEDLINE, EMBASE, and meeting abstracts as per PRISMA guidelines from inception until November 2019. Phase 3 RCTs using AR-antagonists for nmCRPC were included in the final analysis. We used generic inverse variance method and random effects model to calculate the pooled hazard ratio (HR) for distant metastasis or death with 95% confidence interval (CI). Heterogeneity was tested with I2 value and Cochran’s Q test. Results: Three phase 3 RCTs (ARAMIS, PROSPER, and SPARTAN) randomizing 2694 patients in the AR-antagonist arms and 1423 patients in the control arms are included in the final analysis. All studies enrolled only patients with prostate specific antigen (PSA) doubling time of 10 months or less. AR-antagonists used in the study arms were — ARAMIS: darolutamide, PROSPER: enzalutamide, and SPARTAN: apalutamide. Placebo was used in the control arms. All patients continued androgen deprivation therapy (ADT). Randomization was 2:1 in all studies. The pooled HR for distant metastasis or death was highly significant at 0.32 (95% CI: 0.25 - 0.41; P < 0.00001, I2 = 79%) in the favor of AR-antagonist arm in overall population. The pooled HR remained significant when patients were stratified according to PSA doubling time. For patients with PSA doubling time > 6months, the pooled HR was 0.34 (95% CI: 0.27 - 0.43; P < 0.00001, I2 = 0%); for patients with PSA doubling time ≤6 months, the pooled HR was 0.32 (95% CI: 0.25 - 0.41; P < 0.00001, I2 = 73%). Conclusions: Our meta-analysis demonstrated addition of AR-antagonists to ADT significantly prolongs the metastasis-free survival in patients with nmCRPC — an exciting new development in the management of prostate cancer.