ASCO 2012 Report – Abiraterone added to pre-surgical regimen helps eliminate prostate tumor in some men with high-risk prostate cancer

by Bruce Sylvester – In a randomized Phase II study presented at ASCO, investigators reported that 6 months of treatment with the targeted drug abiraterone (Zytiga) when added to standard, pre-surgical hormonal therapy for removal of the prostate has eliminated or nearly eliminated cancer in one-third of the subjects with localized high-risk prostate cancer.

“For this proportion of patients with high-risk disease to have very little to no detectable cancer in the prostate after six months of therapy is dramatic,” said Mary-Ellen Taplin, MD, Associate Professor of Medicine at Harvard Medical School and the Dana-Farber Cancer Institute, Boston, Massachusetts, USA and the study’s lead author. “Our findings suggest that this combination therapy approach could improve outcomes for a substantial number of men, but larger, long-term trials are needed to confirm this approach.”

This is the first  study of abiraterone, a drug used to treat more advanced prostate cancer, for the treatment of earlier-stages of prostate cancer. Abiraterone blocks production of testosterone and related metabolites that can propel prostate cancer growth.  Addition of abiraterone to traditional hormonal therapy, which restricts testosterone production differently, further inhibits the body’s ability to produce the hormones that prostate cancer cells need fro growth.

Localized high-risk disease is prostate cancer with a PSA level above 20, high-grade disease (a Gleason score of 8 or more), and stage T3 disease. Men at this disease stage usually have a poor prognosis.

Prior research shows standard hormonal monotherapy alone, including treatment with leuprolide, before surgery has provided limited benefits for men with localized high-risk prostate cancer.

In this study, the researchers, evaluated the effect of adding abiraterone to leuprolide in two groups of men with with localized high-risk prostate cancer.

Group A included 27 men who received leuprolide hormonal therapy for 12 weeks followed by leuprolide plus abiraterone for another 12 weeks. Group B, included 29 men who received both abiraterone and leuprolide for the entire 24-week period.

Prostate surgery was performed on all subjects after 24 weeks of therapy, and the tissue was examined for evidence of cancer.

The researchers reported that in Group B (24 weeks of abiraterone therapy), 34 percent had either complete elimination (3/29) or nearly complete elimination (7/29) of their cancer at time of surgery. In Group A (12 weeks of abiraterone therapy), 15 percent of men had either complete elimination (1/27) or nearly complete elimination (3/27) of their cancer at time of surgery.

Treatment was well-tolerated by both groups.

The study was supported by Johnson & Johnson.