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 pathologic response to neoadjuvant 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 for September 1, involved 1169 patients who were treated at the researchers’ center from May 1990 to July 2004. Standard BMI criteria were used to divide patients into obese, overweight, and normal/underweight groups.

Compared to normal-weight patients, those in the overweight and the combination of overweight and obesity categories had a reduced likelihood of a complete chemotherapy response, with odds ratios of 0.59 and 0.67, respectively.

Although obese patients were as likely as normal weight patients to have a complete chemotherapy response, they were at greater risk for hormone-negative tumors (p < 0.01), stage III tumors (p < 0.01), and had worse overall survival during a median follow-up period of 4.1 years (p = 0.006). The link between higher BMI and reduced chemotherapy response, the authors note, “may be attributed to the influence of BMI on the clinical effectiveness of chemotherapy or the underdosing of overweight and obese patients by clinicians because of fears or toxicity despite randomized studies that have demonstrated that this practice contributes to worse disease-free survival.” Reference:
J Clin Oncol 2008;26:4072-4077.