By Deborah Kotz, Globe Staff Thousands of women with advanced breast cancer who are being treated with the drug Avastin may be taken off the drug after the US Food and Drug Adminimstration announced today that is revoking the medication’s approval for treatment of breast cancer.The FDA commissioner, Dr. Margaret A. Hamburg, said she based her decision on studies concluding that the drug has not been shown to be safe or life-extending for women with breast cancer that has spread.Avastin will remain on the market to treat other types of cancer — colon, lung, kidney and brain — and doctors can choose to prescribe it off-label for breast cancer patients, but insurance companies may no longer cover the $88,000-a-year therapy. Blue Shield of California already decided to stop covering Avastin for breast cancer patients last month, anticipating that the FDA would drop the approval based on a recent recommendation by its advisory committee to remove breast cancer as one of the drug’s indications. “This was a difficult decision,” Hamburg said in a statement. “After reviewing the available studies it is clear that women who take Avastin for metastatic breast cancer risk potentially life-threatening side effects without proof that the use of Avastin will provide a benefit, in terms of delay in tumor growth, that would justify those risks. Nor is there evidence that use of Avastin will either help them live longer or improve their quality of life.”Patients who take Avastin may experience side effects such as severe high blood pressure; bleeding and hemorrhaging; heart attack or heart failure; and the development of perforations in different parts of the body, such as the nose, stomach, and intestines.Avastin was approved for metastatic breast cancer three and a half years ago under the FDA’s accelerated approval program: This allowed the drug to be used for treatment on a conditional basis, with the understanding that the manufacturer would conduct more studies to ascertain the drug’s risks and benefits and that the drug could have its approval revoked if the trials didn’t show a clear benefit to patients. While one initial study suggested that Avastin could slow tumor growth and extend patient lives, followup studies “showed only a small effect on tumor growth without evidence that patients lived any longer or had a better quality of life compared to taking standard chemotherapy alone,” the FDA said.Avastin manufacturer Genentech did not agree with this assessment and called for a hearing last June, during which the advisory committee voted unanimously against the drug. At a public hearing in August, dozens of breast cancer patients and their families protested outside the FDA headquarters in White Oak, Md., claiming that the drug has had lifesaving benefits.Deborah Kotz can be reached at . Follow her on Twitter @debkotz2.