WASHINGTON – The Food and Drug Administration on Thursday moved toward revoking approval of the blockbuster cancer drug Avastin as a treatment for breast cancer, drawing criticism for limiting treatment options for desperately ill women.

Janet Woodcock, head of the FDA’s drug-approval office, told reporters that four studies indicated that Avastin did not prolong life. “None of the trials showed an improvement in overall survival,” she said.

Existing approvals of Avastin — the world’s best-selling cancer drug — as a treatment for colon, brain, lung and kidney cancer are not affected by the FDA announcement.

The stage for the revocation of Avastin as a breast cancer treatment was set in July, when an FDA advisory committee voted 12-1 to recommend that the agency yank its approval to market the drug for that purpose, citing the clinical trials that showed no benefit.

Avastin has supporters among breast cancer advocacy groups, including the Susan G. Komen Foundation, which issued a statement calling for continued coverage of the drug for women who are benefiting from it.

Avastin was approved for breast cancer in 2008 under a fast-track process to make promising drugs available, subject to further studies. It allows for companies to appeal subsequent FDA decisions to withdraw approval, and Avastin’s maker, Genentech, said on its website that it would do so.