Real-world outcomes in patients with metastatic castration-resistant prostate cancer beyond progression after upfront androgen receptor signaling inhibitor

Background: Upfront androgen receptor signaling inhibitor (ARSI) along with androgen deprivation therapy is the current standard of care for metastatic castration-sensitive prostate cancer. However, evidence on second-line therapy after upfront ARSI is scarce. We aimed to evaluate the oncological outcome of ARSI versus docetaxel (DOC) after upfront ARSI therapy in a real-world clinical practice. Methods: Subjects were metastatic castration-resistant prostate cancer (mCRPC) patients who had progressed within 2 years of upfront ARSI therapy and received ARSI (ARSI group) or DOC (DOC group) as a second-line therapy. Second-line progression-free survival (second-line PFS), and second-line overall survival (second-line OS) were assessed. Propensity score matching (PSM) was used to adjust the clinicopathological features and treatment patterns. Results: A total of 101 mCRPC patients, 68 in the ARSI group, and 33 in the DOC group, were included in this analysis. Median second-line PFS was 6.3 months in the ARSI group and 4.9 months in the DOC group (p = 0.21). Median second-line OS was 25.0 months in the ARSI group and 14.2 months in the DOC group (p = 0.06). Prostate-specific antigen nadir ≤ 0.2 ng/ml during upfront ARSI therapy was significantly associated with improved second-line PFS. After PSM, no significant difference in second-line PFS and second-line OS were observed between the two groups. Conclusion: ARSI or DOC has comparable oncologic outcomes in terms of second-line PFS and second-line OS. Further prospective research with longer follow-ups will be needed to identify the optimal treatment after upfront ARSI therapy.