Initial Gleason Score Does Not Impact Abiraterone Benefit in Prostate Cancer

Overall survival and radiographic progression-free survival trends demonstrate treatment benefit of abiraterone acetate in patients with metastatic castration-resistant prostate cancer (mCRPC) who have or have not received chemotherapy regardless of initial diagnostic Gleason score, a new study published online ahead of print has shown.¹

For the retrospective study, researchers sought to evaluate whether a Gleason score < 8 or ≥ 8 at initial diagnosis is predictive of response to abiraterone acetate plus prednisone in patients with mCRPC.

Researchers analyzed data from 1048 patients who had received docetaxel and 996 chemotherapy-naïve patients treated with abiraterone acetate 1 g plus prednisone 5 mg orally twice daily or placebo plus prednisone.

Results showed that abiraterone acetate treatment significantly improved radiographic progression-free survival, overall survival, prostate-specific antigen (PSA) response, objective response, and time to PSA progression in post-docetaxel patients and chemotherapy-naïve patients regardless of Gleason score at initial diagnosis.

In post-docetaxel patients with a Gleason score < 8, median radiographic progression-free survival was 6.4 months with abiraterone acetate vs 5.5 months with placebo (HR, 0.70; 95% CI, 0.56 – 0.86; P = .0009). Similarly, in those with a Gleason score ≥ 8, median progression-free survival was 5.6 months and 2.9 months, respectively (HR, 0.58; 95% CI, 0.48 – 0.72; P < .0001).

In chemotherapy-naïve patients with a Gleason score < 8, median progression-free survival was 16.5 months with abiraterone and 8.2 months with placebo (HR, 0.50; 95% CI, 0.40 – 0.62; P < .0001), and in those with a Gleason score ≥ 8, it was 13.8 months and 8.2 months, respectively (HR 0.61; 95% CI, 0.49 – 0.76; P < .0001).

The authors concluded that initial Gleason score should not be considered in patients with mCRPC when deciding whether to treat with abiraterone acetate, because metastases may have changed the tumor’s histology from the time of diagnosis.

Reference

1. Fizazi K, Flaig TW, Stöckle M, et al. Does Gleason score at initial diagnosis predict efficacy of abiraterone acetate therapy in patients with metastatic castration-resistant prostate cancer? An analysis of abiraterone acetate phase III trials [published online ahead of print November 25, 2015]. Ann Oncol. doi: 10.1093/annonc/mdv545.