Abiraterone acetate + prednisolone treatment beyond prostate specific antigen and radiographic progression in metastatic castration-resistant prostate cancer patients

Abstract

ObjectivesTo investigate the overall survival (OS) of chemotherapy refractory patients with metastatic castration-resistant prostate cancer who were treated with abiraterone acetate + prednisolone (AA + P) beyond prostate specific antigen (PSA) and radiographic progression (PRP) until clinical progression in comparison to patients treated until PRP. MethodsAt our institute the AA + P treatment started in 2011 in an early-access protocol trial. In October 2012 AA became generally available. From April 2011 to November 2014, 116 patients received AA + P. The clinical trial patients (T; n = 56) were treated beyond PRP until clinical progression. In the nonclinical trial group (NT; n = 57) the treatment was covered until PRP. Three patients are still under treatment. The 2 groups were statistically homogeneous, except AA + P treatment duration. The primary objective was the OS and the secondary the PSA progression-free and radiographic progression-free survivals. ResultsThe median OS was significantly longer (P<0.0001) in the T group compared to the NT group: 21.9 (95% CI: 16.9–25) vs. 12.5 (9.3–14.1) months, respectively. In univariate analysis there were 11 parameters, which significantly affected OS, but in multivariate Cox analysis only alkaline phosphatase (AP) level at the start of treatment, systemic therapy after AA + P and cohort type (T or NT) proved to independently influence the OS. The progression-free survival curves of T and NT groups did not differ significantly. ConclusionsIn our retrospective analysis low levels of AP at the start of treatment, systemic therapy applied after AA + P and treatment beyond PRP proved to be independent factors of longer OS in metastatic castration-resistant prostate cancer.