Survival outcomes and prognostic factors for first-line abiraterone acetate or enzalutamide in patients with metastatic castration-resistant prostate cancer

Abstract Purpose To investigate the survival outcomes of metastatic castration-resistant prostate cancer (mCRPC) patients receiving first-line novel androgen receptor axis-targeted therapies (ARATs) and prognostic factors for patient survival. Methods This retrospective study obtained data from 202 patients who started abiraterone acetate or enzalutamide as first-line therapy for mCRPC between 2016 and 2021 from a single academic center. The primary endpoint was overall survival (OS) defined as the interval from the start of ARAT to death, loss to follow-up, or the end of the study period. The secondary endpoints were PSA decline, PSA nadir, and time to nadir (TTN) after ARATs. Kaplan–Meier survival analyses were applied for depicting OS. Cox proportional hazards model with inversed probability of treatment weighing-adjustment was used to validate the effect of patient, disease, and treatment response factors on OS. Results Among 202 patients, 164 patients were treated with first-line ARATs alone and 38 patients received second-line chemotherapy. The median OS was not reached in patients with first-line ARATs alone and was 38.8 months in those with subsequent chemotherapy after failure from ARATs. OS was not different between the use of abiraterone and enzalutamide, though enzalutamide showed a higher rate of PSA decline ≧ 90% (56% versus 40%, p = 0.021) and longer TTN (5.5 versus 4.7 months, p = 0.019). Multivariable analysis showed that PSA nadir > 2 ng/mL [hazard ratio (HR) 7.04, p