Early PSA response to abiraterone predicts better progression-free and overall survival among patients with metastatic castration-resistant prostate cancer (mCRPC), researchers reported at the 2016 Genitourinary Cancers Symposium in San Francisco.

Carla Cavaliere, MD, of the Istituto Nazionale Tumori IRCCS-Fondazione G. Pascale, in Naples, Italy, and colleagues retrospectively studied 87 mCRPC patients treated with abiraterone. Serum PSA levels were measured after 15 and 90 days and then monthly. Of these, 75 patients were included in their analysis. The investigators observed a PSA decline in 59 patients (78.6%). An early PSA response—a 50% or greater decline from baseline at 15 days—occurred in 42 patients (56%). This early-responder group had a significant72% and 79% decreased risk of disease progression and death, respectively, at 1 year compared with the other patients. The median overall survival was 17.1 months.

In the early responder group, Dr. Cavalier’s group found a positive correlation between overall survival and duration of abiraterone treatment, previous chemotherapy, cumulative dose of docetaxel of 675 mg/m2 or less, and prior hormone therapy duration of 2.5 months or more.

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The researchers concluded that a 50% or greater PSA decline at 15 days after the start of abiraterone treatment can provide clinically meaningful information and could be considered a surrogate of longer progression-free and overall survival.