The addition of abiraterone during 6 months of hormonal therapy prior to surgery eliminated or nearly eliminated tumors in one-third of men with localized high-risk prostate cancer, according to study results.
Abiraterone (Zytiga, Janssen Biotech) traditionally is used to treat advanced prostate cancer. This randomized phase 2 trial was the first to explore its use in early-stage treatment, the researchers said.
“Abiraterone works by blocking production of the male hormone testosterone and related metabolites that often fuel cancer growth,” Mary-Ellen Taplin, MD, associate professor of medicine at Harvard Medical School and Dana-Farber Cancer Institute, said in a press release. “The addition of abiraterone to traditional hormonal therapy, which restricts testosterone production in a different way, further shuts down the body’s ability to produce the hormones that cancer cells need for growth.”
Taplin and colleagues evaluated the effects of adding abiraterone to leuprolide prior to surgical removal of the prostate.
The researchers divided patients into two groups. Group A consisted of 27 men who received leuprolide for 12 weeks, followed by leuprolide plus abiraterone for another 12 weeks. Group B consisted of 29 men who received both leuprolide and abiraterone for the entire 24-week period. All patients underwent prostatectomy after 24 weeks of therapy, and researchers evaluated tissue for evidence of cancer.
Thirty-four percent of men assigned to 24 weeks of abiraterone therapy had either complete elimination or nearly complete elimination of cancer, compared with 15% of men assigned to 12 weeks of abiraterone therapy.
The treatment was well tolerated by both groups, the researchers said. Grade-3 adverse events included elevated aspartate and alanine aminotransferase (9%) and hypokalemia (5%). No grade-4 adverse events were reported.
“Historically, pathologic complete response rate with any type of standard hormone therapy is 5% or less, so these rates are very impressive given the high-risk features of these patients,” Taplin said during a press conference.
The findings suggest that this combination therapy could improve outcomes for a substantial number of men, researchers said.
“The rates of complete response and near-complete response in the prostate were very high in these high-risk prostate cancer patients,” Taplin said during the press conference. “The long-term significance of obtaining a complete response like this needs to be validated in larger studies.”
- Taplin ME. Abstract #4521.
- Dr. Taplin has served as a consultant and adviser to, and received honoraria and research funding from, Johnson & Johnson.