Sequential therapy of abiraterone and enzalutamide in castration-resistant prostate cancer: a systematic review and meta-analysis.

Background: This systematic review and meta-analysis aimed to assess the prognostic value of sequential of abiraterone (ABI) and enzalutamide (ENZ) therapy in patients with castration-resistant prostate cancer (CRPC).
Methods: PUBMED, Web of Science, Cochrane Library, and Scopus databases were searched for articles published prior to December 2019 according to the Preferred Reporting Items for Systematic Review and Meta-analysis statement. Studies were deemed eligible if they compared overall survival (OS), combined progression-free survival (PFS), combined prostate specific antigen (PSA)-PFS, and PSA response rates in CRPC patients receiving sequential ABI/ENZ or vice versa. PSA response to both the first and second agents was defined as a >50% decrease in PSA achieved with each of these agents. Formal meta-analyses were performed for these outcomes.
Results: Ten studies with 1096 patients were eligible for the systematic review and eight studies with 643 patients for the meta-analysis. The ABI-to-ENZ sequence was significantly associated with better PFS (pooled hazard ratio (HR): 0.62, 95% confidential interval (CI): 0.49-0.78, P < 0.001), and PSA-PFS (pooled HR: 0.48, 95% CI: 0.38-0.61, P < 0.001) than the ENZ-to-ABI sequence. PSA response rates of both agents were significantly better with the ABI-to-ENZ sequence (risk ratio: 0.21, 95% CI: 0.09-0.47, P < 0.001). In contrast, treatment sequence was not significantly associated with OS (pooled HR: 0.77, 95% CI: 0.59-1.01, P = 0.055).
Conclusions: ABI-to-ENZ sequential therapy in patients with CRPC was associated with better PFS, PSA-PFS, and PSA response rates. Regardless of sequencing, response to drug therapy was transient for both ABI and ENZ when either agent was used as a secondary therapy. Despite this, treatment sequencing is important to achieve the maximum possible benefit from available drugs in CRPC.