Overweight and obese women with breast cancer may receive reduced doses of chemotherapy drugs, which may put them at greater risk of cancer recurrence, according to a study in the June 13 issue of Archives of Internal Medicine.
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, according to background information in the article. 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, there is evidence that inadequate doses of adjuvant chemotherapy may also contribute to the differences in outcome. 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, the authors write.
Jennifer J. Griggs, M.D., M.P.H., of the University of Rochester, Rochester, N.Y., and colleagues analyzed data on patients with early stage breast cancer treated with adjuvant therapy between 1990 and 2001. They determined the quality of the therapy as measured by the use of reduced doses for the first treatment compared with standard doses, dose proportion over the course of the therapy and the relative dose intensity. There were 9,672 women from 901 practices included in the study. Of the women, 62 percent were above a healthy weight, 31 percent were overweight, 17 percent were obese and 14 percent were severely obese.