Outcomes with abiraterone acetate in metastatic castration-resistant prostate cancer patients who have poor performance status.

Background: Although abiraterone acetate (abiraterone) has proven efficacy in two randomised phase 3 trials in metastatic castration-resistant prostate cancer (mCRPC), patients who had an Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≥2 were either excluded or under-represented in these trials.

Objective: To compare outcomes in ECOG PS 0-1 and ≥2 in mCRPC patients treated with abiraterone.

Design, Setting, And Participants: Cancer registries from three Canadian centres were used to retrospectively identify mCRPC patients (postdocetaxel and docetaxel-naïve) treated with abiraterone. ECOG PS, clinicopathologic characteristics, prostate-specific antigen (PSA) response, and survival data were collected.

Outcome Measurements And Statistical Analysis: Survival outcomes were estimated using the Kaplan-Meier method and compared using the log-rank test. Cox proportional hazards modelling was used to examine the effect of clinicopathologic characteristics on overall survival (OS) and time to PSA progression.

Results And Limitations: A total of 519 patients were identified; 61% (n=318) and 39% (n=201) were ECOG PS 0-1 and ≥2, respectively. ECOG PS 0-1 patients were significantly more likely than PS ≥2 patients to achieve a PSA decline ≥50% from baseline (45% vs 32%; p=0.003, Fisher exact test) and had significantly longer median time to PSA progression (5.2 mo vs 4.1 mo; p=0.023), median treatment duration (7.4 mo vs 4.5 mo; p<0.001), and median OS (20.0 mo vs 9.1 mo; p<0.001). On multivariate analysis, ECOG PS was a significant factor for OS (p<0.001), time to PSA progression (p=0.043), and PSA decline (p=0.002). Potential limitations include the retrospective study design and subjective nature of ECOG PS classification.

Conclusions: ECOG PS ≥2 mCRPC patients treated with abiraterone have inferior outcomes compared with ECOG 0-1 patients, especially in regard to OS. These data indicate that early initiation of abiraterone prior to a decline in PS may be warranted.

Patient Summary: We found that advanced prostate cancer patients who have worse performance status (PS) derive less benefit from abiraterone, indicating that earlier treatment before PS declines could improve outcomes.