In 1999 Judith Layzer’s doctor prescribed the drug Cetrotide to treat her ovarian cancer. Her employee health plan paid for the Cetrotide, even though the Food and Drug Administration had approved the drug only for infertility, not cancer.

When Layzer, 67, who lives in Manhattan,  enrolled in a Medicare prescription drug plan in 2006 , the new insurer denied coverage because she was using the drug off-label. Medicare doesn’t cover drugs that are not prescribed for a “medically accepted indication.”

The nonprofit Medicare Rights Center filed suit in U.S. District Court for the Southern District of New York last November on Layzer’s behalf, charging that excluding off-label prescriptions from the Medicare-approved drug list hurts the “most vulnerable people with Medicare.” According to the center, off-label prescribing is not only permitted nationwide, it is also covered by 42 state Medicaid programs and almost all private employer-based insurance plans.

“Standard medical practice routinely relies on off-label medications to treat serious illness,” says Robert M. Hayes, president of the Medicare Rights Center. He adds that Medicare should force, as Congress intended, private Medicare drug plans to cover medicines that doctors prescribe.

“So long as there is professional support for a drug’s use,” Hayes says, “the treating physician—not a profit-making insurance company—should determine what medicine a patient takes.”