Two large studies of the top-selling cancer drug Avastin released Wednesday show that the drug can slow the growth of ovarian cancer when added to chemotherapy.
But neither found that the expensive drug extends life expectancy.
"The amount of improvement seems to be relatively modest," said Amit Oza, an oncologist at the Princess Margaret Hospital in Toronto who led one of the studies set to be published today in the New England Journal of Medicine.
Even these modest results energized patient advocates, who note the lack of new treatments for ovarian cancer, which causes about 15,000 deaths a year in the United States and is the eighth most common cancer among women.
"While we are looking for that silver bullet, this is a gift that shouldn't be overlooked," said Karen Orloff Kaplan, chief executive of the Ovarian Cancer National Alliance.
Data on survival is still being collected, but the results so far are likely too disappointing for the drug's maker, Genentech, to seek Food and Drug Administration approval of Avastin use for ovarian cancer, said company spokeswoman Charlotte Arnold. However, the company did receive approval this month from European drug authorities to market Avastin for ovarian cancer treatment there.
Both studies hinted that patients with advanced ovarian cancer may benefit more than patients with earlier-stage disease.
"There are likely to be subsets of patients with very advanced ovarian cancer who will experience a survival benefit as long as they're being treated with Avastin," said Robert A. Burger, an oncologist at Fox Chase Cancer Center in Philadelphia who helped lead the second study.
But sorting out patients who might benefit from those who won't is impossible for now.
"We desperately need to figure out a way to predict the folks who are going to respond to the drug versus the folks who will only get side effects of the drug," said Otis Brawley, chief medical officer of the American Cancer Society.
Studies searching for such a test are ongoing.
One of the two studies followed 1,500 women in 11 countries. All received standard chemotherapy, and half received Avastin for up to 10 months after chemotherapy. In the Avastin patients, the drug halted the growth of their tumors for an extra month and a half.
The second study of 1,800 women used a higher dose of Avastin added to chemotherapy. The women who continued receiving Avastin for 10 months after chemotherapy experienced an extra four months of slow to no growth in their tumors, compared with the women who received no Avastin.
But slowing the tumors did not delay death from ovarian cancer.
The FDA approved Avastin in 2004 as the first in a much-heralded class of biological drugs designed to halt cancer by cutting off a tumor's blood supply.
Kidney cancer patients benefit the most from Avastin. But in more common cancers, such as lung and colorectal cancer, "the beneficial effect really remains modest," said Yihai Cao, a cancer biologist at the Karolinska Institute in Stockholm.
In November, the FDA removed a preliminary approval for Avastin for advanced breast cancer. The agency's head, Margaret A. Hamburg, said the risks of Avastin outweighed the benefits.