Abiraterone Acetate Prolongs Survival in Metastatic Prostate Cancer

Debra Wood, RN

April 2011, Vol 2, No 2 - Genitourinary Cancers Symposium

Howard I. Scher, MDOrlando, FL—Abiraterone acetate holds promise of improving survival in patients with metastatic castrationresistant prostate cancer across multiple patient subgroups, according to Howard I. Scher, MD, chief of the Genitourinary Oncology Service, Sidney Kimmel Center for Urologic and Prostate Cancers at Memorial Sloan-Kettering Cancer Center, New York City, who reported results of a trial at the session “Prostate Cancer for the Recurrent Disease” at the 2011 Genitourinary Cancers Symposium.

“Abiraterone acetate prolongs overall survival of men with metastatic castration- resistant prostate cancer who have progressed after docetaxel-based chemotherapy, with a 35% reduction in mortality,” said Dr Scher.

The drug is currently under review by the US Food and Drug Administration (FDA) and the manufacturer said that an FDA decision is expected later this year.

Early clinical studies suggested abiraterone acetate, a selective androgen biosynthesis inhibitor blocking the action of CYP17, restrains persistent androgen synthesis from adrenal and intratumoral sources, thereby suppressing a growth stimulus for meta static castration-resistant prostate cancer.

In a randomized, double-blind study, Dr Scher and an international team compared abiraterone acetate 1000 mg daily and prednisone 5 mg twice daily with placebo and prednisone in 1195 men with metastatic castration-resistant prostate cancer, progressing after receiving docetaxelbased chemotherapy. Patients previously treated with ketoconazole or more than 2 previous chemotherapy regimens were excluded from the study. The 2 cohorts were well balanced in terms of age, race, performance status, pain, previous chemotherapy regimens, type of progression, and extent of disease.

In August 2010, after interim results showed significant improved overall survival in the active cohort, the study was unblinded, and men in the placebo group were offered abiraterone acetate. “The favorable effect on overall survival was observed across multiple patient subgroups, including those with 1 prior chemotherapy, visceral disease, as well as a pain intensity of 4 or greater,” Dr Scher said.

Nicholas J. Vogelzang, MD, head of the Section of Genitourinary Cancer at the Nevada Cancer Institute in Las Vegas, said at the meeting that continuing the long trial was a waste of lives and money, because the researchers, of which he was an investigator, saw the agent was active after 10 to 12 patients.

Adverse events were similar in the 2 cohorts. Fluid retention and hypo kalemia were the 2 most common ad verse reactions in the abiraterone group, but they were typically low grade. There was a slight 2% increase in cardiac disorders, primarily tachycardia and atrial fibrillation, in the treatment group, but Dr Scher said, the cardiac conditions were easily managed.

A. Oliver Sartor, MD, Professor of Medicine at Tulane University in New Orleans and co-chair of the session, commented that abiraterone acetate will be a “game changer” in treating men with metastatic castration-resistant prostate cancer.

“It will provide a new alternative for patients with castration-resistant prostate disease postdiagnosis,” Dr Sartor said. “It will change practice.”