Dr. Birrer on the Approval Process in Ovarian Cancer

Michael Birrer, MD, PhD, professor of medicine, Harvard Medical School, director, Gillette Center for Gynecologic Oncology, Massachusetts General Hospital, explains how the endpoints of progression-free survival (PFS) and overall survival (OS) are holding back the approval of drugs for patients with ovarian cancer.

Fortunately, patients with ovarian cancer demonstrate an initial response rate of 75% to 80% with a long duration of disease-free survival, Birrer says. Unfortunately, 75% to 80% of women with advanced-stage ovarian cancer eventually recur, develop drug resistance disease, and die.

Birrer says in order to test drugs upfront, pharmaceutical companies spend up to hundreds of millions of dollars on a phase III clinical trial. Ascertaining an endpoint of OS generally takes 6-7 years and is generally reached with confounding variables, such as crossover. Because of this, PFS is an attractive endpoint for drug development in this space, since it requires less time to fulfill.

Bevacizumab, which has not been approved in the United States to treat ovarian cancer, has been tested in 8,000 women around the world in various randomized phase IIItrials. Birrer says the results of those trials have all shown a positive primary endpoint of PFS but OS has not yet been shown. Researchers believe this occurs because of interactions between bevacizumab and other drugs or as the result of inadequate administration duration.

Birrer believes that bevacizumab should be considered an effective treatment for patients with advanced-stage ovarian cancer. The ideal indication for bevacizumab, Birrer believes, is in the frontline setting before patients become unfit for treatment.