WEDNESDAY, Oct. 1, 2003 (HealthDayNews) -- Tamoxifen, the drug that blocks estrogen, works as well in obese women with early-stage, hormone-responsive breast cancer as in leaner women.
The new research, published in the Oct. 1 issue of the Journal of the National Cancer Institute, refutes earlier studies that found an increased risk of cancer recurrence and death among obese women on tamoxifen compared to women who are leaner.
But the other studies compared women in all stages of breast cancer, says James J. Dignam, the lead researcher from the University of Chicago.
In the new study, Dignam says, "we looked at women with early-stage breast cancer, so-called node-negative, with totally localized tumors." The tumors were the type known to respond to tamoxifen, a drug taken orally which works by binding to estrogen receptors, thus preventing estrogen from binding to them. When this happens, the cancer cells that depend on estrogen to divide stop growing and thus die.
Dignam's team evaluated 3,385 women with early-stage breast cancer who were assigned to receive either tamoxifen or placebo after having surgery for the breast cancer. They looked at the association between obesity and the risk of breast cancer recurrence in the breast affected, in cancer in the opposite breast, of new cancers, and of overall death rates.
After a median follow-up of nearly 14 years, they found that obese women had no higher risk of recurrence of the original breast cancer or death attributable to the breast cancer than did leaner women. Obese women are those with a body mass index (BMI) of 30 or above. A five-foot-five woman who weighs 180 pounds has a BMI of 30.
"Obese and lean women got equal benefit in the reduction of the tumor," Dignam says. "But there were some negative consequences of obesity," he adds.
Obesity was associated with an increased risk of getting cancer in the opposite breast, of getting other cancers, and of dying from other causes, they found.
During the follow-up period, obese women were 1.5 times more likely to get cancer in the opposite breast than were lean women, 1.6 times more likely to get cancers at other sites and 1.3 times more likely to die from all causes than leaner women.
The study, Dignam says, points to the value of weight loss among breast cancer survivors who are obese, even though their obesity doesn't seem to affect how well the tamoxifen works. "Weight reduction and maintenance could have long-term benefits for breast cancer survivors," he says.
Another expert says the study findings will motivate her to urge her obese patients with breast cancer to lose weight. "Up until now, my main emphasis [to overweight patients] has been on not gaining weight," says Dr. Patricia Ganz, director of the Division of Cancer Prevention and Control at the UCLA Jonsson Cancer Center in Los Angeles. "Now, I will encourage them to lose weight. Losing weight may be an important part of the treatment strategy."
This is one of the first studies that finds what a woman weighs when she is diagnosed with breast cancer has an influence on survival and how well she does, Ganz adds.
Tamoxifen (sold under the brand name Nolvadex) is typically taken daily in pill form, usually for five years, according to the American Cancer Society. Its use after surgery can reduce the chances of the breast cancer coming back, several studies have shown.
More information
For information on tamoxifen therapy for breast cancer, try the American Cancer Society. For general information on the disease, visit the National Cancer Institute.
