Application of abiraterone acetate (AA) in chemo-naïve metastatic castration-resistant prostate cancer (mCRPC) patients who did not fulfil the patient inclusion criteria in the COU-AA-302 study.

Abstract

317 Background: Visceral metastases or poor performance status (ECOG 2 or above) were the major exclusion criteria in the COU-AA-302 study, and hence the efficacy of abiraterone acetate (AA) in chemo-naïve mCRPC patients with these characteristics remain undetermined. Our study compares the clinical efficacy of AA in chemo-naïve mCRPC patients with or without the aforementioned characteristics. Methods: The clinical records of chemo-naïve mCRPC patients from all 6 public oncology centers in Hong Kong between August 2011 and December 2014 were reviewed. Patients with visceral disease who were medically unfit for, or who declined, chemotherapy, were allowed for AA in the study period. The median overall survival (OS), progression-free survival (PFS), patient and disease characteristics were compared between groups which satisfied, and did not satisfy, the inclusion criteria of COU-AA-302 study. Results: Fifty-eight consecutive chemo-naïve mCRPC patients had received AA in the review period, of which 29 fulfilled the inclusion criteria for the COU-AA-302 study (Group Eligible). All the remaining patients (Group Ineligible) had ECOG 2 or above, including 3 who had non-nodal visceral metastases. Group Ineligible had higher baseline PSA, haemoglobin and alkaline phosphatase level than Group Eligible, but otherwise there was no significant difference in the baseline characteristics between the groups for age, Gleason score, and co-morbidities. Group Ineligible had significantly shorter OS than Group Eligible (7.7 vs 25.0 months, p = 0.0095) and also a shorter PFS that did not reach statistical significance (5.3 vs 9.8 months, p = 0.2936). The duration of use of AA, and frequency of employment of post-AA treatment were comparable between the groups. Conclusions: Our study demonstrated a poor efficacy of AA in chemo-naïve patients who did not fulfil the inclusion criteria for COU-AA-302 study, by virtue of poor performance status or presence of visceral metastases. The impact of AA in this group of patients warrants further examination in clinical trials before its routine clinical use in this subgroup.