Health: Breast Cancer's 'New Era'

Breast cancer patients deserve good news, and they got a nice helping of it last week when a large, international clinical trial was halted early because the drug being tested was found to dramatically reduce the risk of relapse. The findings for the drug, letrozole, manufactured by Novartis and sold under the brand name Femara, electrified researchers and prompted them to abort the double-blind study of 5,187 postmenopausal women with early-stage disease and offer the treatment to the 2,594 patients who had been receiving a placebo. "This is the beginning of a new era in breast-cancer therapy," says Dr. Paul Goss, of Princess Margaret Hospital in Toronto, who directed the project.

Stopping such a big and important study is exceptional, but so were the results: letrozole reduced the risk of recurrence among older women by 43 percent. (Most of the 211,000 women diagnosed with breast cancer in the United States each year are postmenopausal.) Goss and his colleagues in the United States and Europe were testing the drug as a follow-up treatment. The women in the letrozole study had recently completed (after surgery) the standard five-year course of tamoxifen, a powerful and widely used drug that eventually loses its effectiveness as, researchers believe, tumors become resistant to it. Until now, breast-cancer patients who finished tamoxifen treatment could only wait and hope that their cancer wouldn't recur, which it does, within five years, in up to 20 percent of such cases. Letrozole, previously approved by the FDA for advanced breast cancer and readily available, offers an exciting new option for extending treatment of early-stage disease. "If it raises my chances even 1 percent, I say sign me up," says Debbie Lloret, 46, a Staten Island, N.Y., mother and breast-cancer survivor who has had two lumpectomies, a mastectomy, chemotherapy and is currently in her third year of tamoxifen. "I am so excited about this I can't even tell you."

Including breast-cancer patients who have been off tamoxifen for a year or two, as many as 300,000 American women could benefit from starting letrozole immediately, says Goss. Letrozole, like tamoxifen, works by interfering with the hormone estrogen, which feeds breast-cancer cells; tamoxifen blocks estrogen receptors on the cells, while letrozole inhibits the creation of estrogen. (Letrozole is not effective when given alone to premenopausal women who ovulate, because they produce much more estrogen than do postmenopausal women.)

Letrozole has side effects similar to those women experience during menopause, including hot flashes and osteoporosis. The study recommends that women receiving letrozole take calcium and vitamin D and have a doctor monitor their bone density.

The news about letrozole is an exciting development for breast cancer patients, but it is not the last word on the drug. An editorial accompanying the report (released early by The New England Journal of Medicine) notes that while "letrozole is generally well tolerated, concern about the consequences of long-term use remains." Goss points out that the study was never intended to examine long-term effects. His research group will continue to track the patients in the study, he says, and adds that so far there is no evidence of serious toxicity. New studies will have to be done to look at the potential risks and benefits of using letrozole for periods longer than five years.

All of which means, as breast-cancer patients and their families know so well, proceed with caution. "This is no magic bullet and it is not the end of the journey," says Dr. Andrew von Eschenbach, director of the National Cancer Institute, which led the study in the United States. "There is much, much more to do. It is one step, but it is an important step."