Outcomes of First-Line Abiraterone Acetate or Enzalutamide for Older Adults With Metastatic Castration-Resistant Prostate Cancer According to Use of Upfront Docetaxel for Metastatic Castration-Sensitive Prostate Cancer in an International Multicenter Registry: A SPARTACUSS-Meet-URO 26 Study

This study evaluates treatments for metastatic castration-resistant prostate elderly (aged >_ 75). Analyzing 337 patients, no significant difference in survival or safety have been found between patients treated with abiraterone acetate plus prednisone or enzalutamide, regardless of prior docetaxel use. This suggests similar efficacy and tolerability in a population of patients with limited clinical data. Background: Managing metastatic castration-resistant prostate cancer (mCRPC) in men aged >_ 75 is challenging due to limited data. Regardless of age, in real-world clinical practice, most mCRPC still derive from failure of androgen deprivation therapy (ADT) with or without docetaxel (D) for metastatic castration-sensitive prostate cancer (mCSPC). As abiraterone acetate plus prednisone (AA) and enzalutamide (Enza) are common first-line treatments for mCRPC. The impact of prior use of D for mCSPC on the efficacy and safety of AA or Enza in this older population remains unclear. Methods: A cohort of patients aged > 75 years starting AA or Enza as first-line therapy for mCRPC from January 2015 to April 2019 was identified from the registries of 10 institutions. Patients were categorized into 2 groups based on previous use of D for mCSPC. Primary endpoints were cancer-specific survival (CSS) from AA or Enza start, CSS from ADT onset, and safety. We used Kaplan-Meier method to estimate the endpoints distribution, including median values with 95% confidence intervals (95% CI). Results: Of the 337 patients identified, 24 (7.1%) received ADT + D and 313 (92.9%) received ADT alone for mCSPC. Median follow-up from AA/Enza start was 18.8 months. Median CSS from ADT or AA/Enza was not significantly different between ADT + D and ADT alone cohorts (71.9 vs. 52.7 months, P = .97; 25.4 vs. 27.2 months, P = .89, respectively). No statistically significant difference in adverse events (AEs) of any grade rate (58.3% vs. 52.1%, respectively; P = .67) or grade > 3 (12.5% vs. 15.7%, respectively; P = 1.0) was found between ADT + D and ADT alone cohorts. Conclusions: Despite the innate limitations of a retrospective design and relatively small size of the ADT + D cohort, this analysis suggests that elderly men receiving AA or Enza as first-line therapy for mCRPC have similar survival outcomes and tolerability, regardless of previous D for mCSPC.