Undertreatment of obese women receiving breast cancer chemotherapy.

BACKGROUND Systematic undertreatment of breast cancer in overweight and obese women may contribute to the poorer prognosis in these women. The objective of this study was to investigate treatment patterns in overweight and obese women undergoing breast cancer adjuvant chemotherapy. METHODS We performed a retrospective cohort study of 9672 women treated with doxorubicin hydrochloride and cyclophosphamide between 1990 and 2001. The main outcome measure was the quality of chemotherapy as measured by the use of reduced doses for the first treatment (compared with standard doses), the overall dose proportion (actual-expected dose ratio), and relative dose intensity. RESULTS First-cycle dose reductions (defined as a dose proportion of <0.9 compared with standard published doses) were administered to 9% of the healthy weight, 11% of the overweight, 20% of the obese, and 37% of the severely obese women (P<.001). First-cycle reduction was independently associated with being overweight (P = .03), obese (P<.001), severely obese (P<.001), older than 60 years (P<.001), and having a serious comorbid condition (P = .03). Practices varied greatly in the use of dose reductions in overweight and obese patients. Severe obesity was independently associated with a lower likelihood of admission for febrile neutropenia, even among those subjects given full weight-based doses (odds ratio, 0.61; 95% confidence interval, 0.38-0.97). CONCLUSIONS Overweight and obese women with breast cancer often receive intentionally reduced doses of adjuvant chemotherapy. Administration of initial and overall full weight-based doses of adjuvant chemotherapy in overweight and obese women is likely to improve outcomes in this group of patients.