Washington ? Federal regulators are considering taking the highly unusual step of rescinding approval of a drug that patients with advanced breast cancer turn to as a last-ditch hope.

The debate over Avastin, prescribed to about 17,500 women with breast cancer a year, has become entangled in the politically explosive struggle over medical spending and effectiveness that flared during the battle over health care reform: How should the government balance protecting patients and controlling costs without restricting access to cutting-edge, and often costly, treatments?

The Food and Drug Administration is reviewing the recommendation of influential scientific advisers to revoke authorization of the drug to treat metastatic breast cancer. Contrary to initial research, new studies indicate that the benefits of the expensive drug, which costs $8,000 a month, do not outweigh its risks, the advisory panel concluded.