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15 June 2005
Obesity Increases Risk Of Breast Cancer Recurrence 
Overweight and obese women with breast cancer may receive reduced doses of chemotherapy drugs, which may put them at greater risk of cancer recurrence, says a study in the Archives of Internal Medicine. The article suggests that women who are 20 to 25 percent over their ideal body weight have a 1.3 times greater risk of a recurrence of breast cancer. Differences in body chemistry in overweight and obese women, including differences in estrogen and insulin levels, may account for their poorer prognosis, but the authors suggest that there is evidence that inadequate doses of adjuvant chemotherapy may also contribute to the differences. Adjuvant chemotherapy is given to women with no measurable spread of the cancer beyond the primary tumor to improve the likelihood of disease-free and overall survival. Physicians may deliberately reduce dosage levels, which are calculated on the basis of body weight, for heavier women because of fears of toxic effects, say the researchers. The study, led by Jennifer J. Griggs of the University of Rochester, analyzed data on patients with early stage breast cancer treated with adjuvant therapy. Of the women, 62 percent were above a healthy weight, 31 percent were overweight, 17 percent were obese and 14 percent were severely obese. Among the severely obese women, 37 percent had a first-cycle dose reduction of at least 10 percent, compared with 20 percent of obese women, 11 percent of overweight women and nine percent of healthy weight women. "Given the evidence that maintaining dose intensity improves the likelihood of overall and disease-free survival and the lack of data supporting dose reductions in overweight and obese women, it is likely that the practice variations we have observed represent 'unwarranted variation' in the adjuvant treatment of patients with breast cancer. The incidence of obesity, particularly severe obesity, is increasing in the United States. Eliminating unwarranted dose reductions will therefore become increasingly important in defining best practices for the care of overweight and obese women," the researchers concluded.
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