Interim results of a randomized, controlled, phase 3 trial showed that abiraterone acetate significantly prolonged overall survival (OS) in patients with metastatic castration-resistant prostate cancer (CRPC) who progressed after docetaxel-based chemotherapy. The survival benefit was consistent across all prespecified subgroups. Lead author Howard Scher, MD, Memorial Sloan-Kettering Cancer Center, New York, said abiraterone is poised to become a new standard of care.
The study enrolled 1200 patients with metastatic CRPC who failed on docetaxel and ≤1 additional chemotherapy regimen. Patients were randomized to abiraterone and prednisone or prednisone and placebo. Groups were well balanced for demographic and disease characteristics.
Patients on abiraterone achieved significantly superior median OS versus placebo (14.8 months vs 10.9 months; P <.001), representing a 35% reduction in the relative risk of mortality. Preplanned analyses found survival benefit consistent across all subgroups, regardless of prior chemotherapy lines, performance status, pain scores, and radiographic progression-free survival. The abiraterone group also had higher rates of total and confirmed responses according to prostate-specific antigen (PSA) testing. Rates of overall and serious adverse events were similar between both groups and considered manageable.
Oliver Sartor, MD, Tulane University School of Medicine, New Orleans, Louisiana, moderated the prostate cancer session. “This is a game-changer. To me this will change practice,” he said.
Positive 42-month data were also presented for MDV3100, a novel, tripleacting, oral androgen-receptor antagonist for CRPC. In a phase 1/2 study, MDV3100 demonstrated durable antitumor activity, based on median times to PSA and radiographic progression.
Higano and associates enrolled 140 men with progressive disease resistant to standard antiandrogen treatments, such as bicalutamide. As of the meeting, 18 men remained on active treatment. Median time to PSA progression was 316 days in the postchemotherapy group and not yet reached in the chemotherapynaïve cohort. Median time to radiographic progression was 392 days versus 175 days, respectively. Circulating tumor cell counts remained favorable for 91% of patients with favorable counts at baseline, and counts for 15 patients went from unfavorable to favorable.
MDV3100 is currently being studied in the randomized phase 3 AFFIRM and PREVAIL trials. Both trials are actively recruiting patients
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