Racial/Ethnic and Socioeconomic Differences in Colorectal and Breast Cancer Treatment Quality The Role of Physician-level Variations in Care

Background: Despite a large body of research showing racial/ethnic and socioeconomic disparities in cancer treatment quality, the relative role of physician-level variations in care is unclear. Objective: To examine the effect of physicians on disparities in breast and colorectal cancer care. Subjects: Linked SEER Medicare data were used to identify Medicare beneficiaries diagnosed with colorectal and breast cancer during 1995-2007 and their treating physicians. Research Design: We identified treating physicians from Medicare claims data. We measured the use of NIH guideline-recommended therapies from SEER and Medicare claims data, and used logistic models to examine the relationship between race/ethnicity, socioeconomic status, and cancer quality of care. We used physician fixed effects to account for between-physician variations in treatment. Results: Minority and low socioeconomic status beneficiaries with breast and colorectal cancer were less likely to receive any recommended treatments as compared with whites. Overall, between-physician variation explained <20% of the total variation in quality of care. After accounting for between-physician differences, median household income explained 14.3%, 18.4%, and 13.2% of the variation in use of breast-conserving surgery, chemotherapy, and radiation for breast cancer, and 13.7%, 12.9%, and 12.6% of the within-physician variation in use of colorectal surgery, chemotherapy, and radiation for colorectal cancer, whereas race and ethnicity explained <2% of the within-physician variation in cancer care. Conclusions: Between-physician variations partially explain racial disparities in cancer care. Residual within-physician disparities may be due to differences in patient-provider communication, patient preferences and treatment adherence, or unmeasured clinical severity.