Obesity Linked to Poor Prognosis for Some Breast Cancer Patients
FRIDAY March 14, 2008 -- Women who are overweight or obese when diagnosed with locally advanced breast cancer face a higher chance of recurrence and a shorter life expectancy than either normal or underweight patients, a new study suggests.
The researchers also found that obese patients are more likely than overweight, normal or underweight patients to be diagnosed with a rare, aggressive and deadly form of locally advanced breast cancer, known as inflammatory breast cancer (IBC).
"We already know that obesity is a risk factor for many diseases, and now we're showing that women who are obese or overweight essentially face a higher risk for getting a more aggressive form of breast cancer, and progress faster and die faster from their disease," said study senior author Dr. Massimo Cristofanilli. He is an associate professor in the department of breast medical oncology at the University of Texas M.D. Anderson Cancer Center in Houston.
The findings are published in the March 15 issue of Clinical Cancer Research.
Locally advanced breast cancer (LABC), which is cancer that has spread to nearby tissue or lymph nodes, accounts for about 5 percent of all breast cancers in the United States. In medically underserved parts in the country and the developing world, about half of all breast cancer cases are LABC, the researchers said.
The even more lethal IBC form of breast cancer strikes between 1 percent and 2 percent of U.S. breast cancer patients.
Noting that six in 10 Americans are obese or overweight, Cristofanilli and his colleagues explored possible weight-cancer connections by analyzing data on 606 women who had received similar care for stage III locally advanced breast cancer at M.D. Anderson between 1974 and 2000.
Records of body-mass index revealed that two-thirds of the patients were either overweight or obese at diagnosis. Slightly more than 80 percent of the patients had standard locally advanced breast cancer, while 18 percent had the more deadly IBC disease.
Comparing weight records with disease statistics, the researchers found that a greater proportion of obese patients were diagnosed with IBC compared with either overweight or normal/underweight patients.
Among all patients with locally advanced breast cancer, overweight or obese women were more likely to have a higher grade of breast cancer at diagnosis, followed by more disease recurrence and shorter survival times.
Cristofanilli and his colleagues noted that they tracked BMI status only at diagnosis, not during subsequent treatment. Still, they concluded that obese and overweight women coping with locally advanced breast cancer could benefit from the inclusion of a dietary component in their treatment regimen.
"Obesity is a major issue for our society, and it raises the possibility that perhaps if we reduce excess weight, we might reduce the incidence of breast cancer in the first place," said Cristofanilli. "And for those already diagnosed, lifestyle modification and weight control -- and probably more aggressive follow-up -- might be needed in addition to chemotherapy and other standard treatments."
But Dr. Harold J. Burstein, an assistant professor of medicine at Harvard Medical School and the Dana-Farber Cancer Institute in Boston, cautioned that the evidence suggesting a link between obesity and poor breast cancer outcomes is "less than overwhelming."
"There's a lot of suggestive data, but there's nothing that's absolutely definitive," he said. "That is not to say that there is anything to suggest that it is risky for breast cancer patients to make an effort to maintain their weight through food control and exercise. And it can certainly help strengthen bones and lower the risk for diabetes and heart disease, which is all the better."
"But it really must be said that there are women who torment themselves if they are obese at diagnosis or gain weight afterwards, because they believe they are jeopardizing their outcome, Burstein said. "Yet the honest assessment is that we don't really understand yet whether there is a relationship between obesity and breast cancer outcomes, or how strong the relationship is."
For more on the connection between obesity and cancer, visit the U.S. National Cancer Institute.
Posted: March 2008