Effect of Patient Socioeconomic Status and Body Mass Index on the Quality of Breast Cancer Adjuvant Chemotherapy

The purpose of this study was to investigate the relationship between socioeconomic status (SES) and the use of intentionally reduced doses of chemotherapy in the adjuvant treatment of breast cancer. Patients with breast cancer treated with a standard chemotherapy regimen (n = 764) were enrolled in a prospective registry after signing informed consent. Detailed information was collected on patient, disease, and treatment, including chemotherapy doses. Zip code level data on median household income, proportion of people living below the poverty level, and educational attainment were obtained from the US Census. Doses for the first cycle of chemotherapy lower than 85% of standard were considered to be reduced. Univariate analyses and multivariate logistic regression were performed to identify factors associated with the use of reduced first cycle doses. In univariate analysis, individual education attainment, zip code SES measures, body mass index, and geographic region were all significantly associated with receipt of intentionally reduced doses of chemotherapy. In multivariate analysis, controlling for geography, factors independently associated with reduced doses were obesity (odds ratio [OR], 2.47; 95% CI, 1.36 to 4.51), severe obesity (OR, 4.04; 95% CI, 1.46 to 11.19), and education less than high school (OR, 3.07; 95% CI, 1.57 to 5.99). Social disparities in breast cancer outcomes may be in part the result of lower quality chemotherapy doses in the adjuvant treatment of breast cancer. Efforts to address such prescribing patterns may help reduce SES disparities in breast cancer survival.