(Reuters) - Health insurer Blue Shield of California has decided not to pay for Roche Holding's drug Avastin to treat breast cancer after health advisers said it was not safe or clinically beneficial.

Blue Shield of California, an insure with around 3.3 million members, said in a notice posted on its web site that the drug would no longer be covered as a treatment for metastatic breast cancer beginning October 17. It said exceptions may be considered on a case-by-case basis.

The Food and Drug Administration in June unanimously rejected use of Avastin for breast cancer.

Their vote endorsed an FDA move in December to revoke its approval for Avastin in breast cancer. FDA Commissioner Margaret Hamburg is due to make a final decision later.

Without FDA approval, other insurers and government health programs likely will stop covering the $8,000-a-month drug.

Avastin won U.S. clearance for the disease in 2008 based on a study showing the drug stalled breast cancer growth by 5.5 months more when used in combination with standard chemotherapy. As part of an accelerated approval, the FDA required Roche to run follow-up studies.

Later studies found only a one- to three-month delay in breast cancer growth. None of the studies showed Avastin extended the lives of patients with advanced breast cancer.

Some patients also had severe side effects, including holes in the stomach and intestines, severe bleeding and blood clots. The company says the incidence of these serious side effects was just under 3 percent greater for those taking Avastin.

Roche was not immediately available for comment.

(Reporting by Michael Erman in New York)

Mochila insert follows.