NEW YORK (Reuters Health) - New research indicates that overweight patients with operable breast cancer are less likely than their normal-weight peers to achieve a complete response with chemotherapy.

Prior research has linked obesity with worse breast cancer outcomes, but the mechanisms involved were unclear, note Dr. Abenaa M. Brewster and colleagues from the University of Texas M. D. Anderson Cancer Center in Houston.

The current investigation, reported in the Journal of Clinical Oncology, involved 1,169 patients who were treated at the researchers' center from May 1990 to July 2004. Standard body mass criteria were used to divide patients into obese, overweight, and normal/underweight groups. This included body mass index (BMI) -- the ratio of height to weight, used to determine if someone is within a normal weight range or is underweight, overweight or obese.

Compared to normal-weight patients, those in the overweight and the combination of overweight and obesity categories had a reduced likelihood of a complete response with chemotherapy response.

Although obese patients were as likely as normal-weight patients to have a complete chemotherapy response, they were at greater risk for hormone-negative, stage III tumors and had worse overall survival over a follow-up period of 4.1 years.

The link between a higher BMI and a reduced chemotherapy response, the authors note, "may be attributed to the influence of BMI on the clinical effectiveness of chemotherapy" or to the under-dosing of overweight and obese patients because of a physician's fear of toxicity, even though studies have shown that this contributes to lower rates of disease-free survival.

SOURCE: Journal of Oncology, September 20008.

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