The sequence in which abiraterone and enzalutamide are administered to chemotherapy-naive patients with metastatic castration-resistant prostate cancer (mCRPC) may not have an impact on outcomes, according to a study published in Clinical Genitourinary Cancer.1
Androgen receptor–targeting agents such as abiraterone and enzalutamide are being used with increasing frequency in patients with mCRPC because of their efficacy, favorable safety profile, and ease of administration, but no studies have directly evaluated the effect administration order may have on outcomes.
For this retrospective analysis, researchers assessed the outcomes of 97 patients with mCRPC who were treated with abiraterone followed by enzalutamide and vice versa. Patient characteristics were well-balanced between the study arms at time of study initiation. Median follow-up was 17.7 months.
There was no significant difference in prostate-specific antigen (PSA) response rate between abiraterone (48%) and enzalutamide (51%) after 1st-line treatment (P = .840), but a significant difference was observed after 2nd-line treatment (abiraterone, 6.4% vs enzalutamide, 30%; P = .004).
The median combined progression-free survival (PFS) was 11.1 months and 9.04 months in the abiraterone-enzalutamide arm and the enzalutamide-abiraterone arm, respectively. No significant difference was observed in median combined PFS between the 2 study groups (hazard ratio [HR], 0.71; 95% CI, 0.46-1.08; P = .105).
No significant difference was observed in median overall survival (OS; HR, 0.98; 95% CI, 0.64-1.52; P = .834).
The results suggest that the order in which abiraterone and enzalutamide are administered does not have a significant impact on 1st-line and 2nd-line PFS, combined PFS, and OS.
- Matsubara N, Yamada Y, Tabata K, et al. Abiraterone followed by enzalutamide versus enzalutamide followed by abiraterone in chemotherapy-naive patients with metastatic castration-resistant prostate cancer. Clin Genito Canc. 2017 Sep 23. doi: 10.1016/j.clgc.2017.09.008 [Epub ahead of print]