Residual treatment disparities after oncology referral for rectal cancer

Background: Black patients with rectal cancer are considerably less likely than white patients to receive adjuvant therapy. We examined the hypothesis that the lower treatment rate for blacks is due to underreferral to medical and radiation oncologists. Methods: We used 1992-1999 Surveillance, Epidemiology, and End Results-Medicare data to identify elderly (≥66 years of age) patients who had been hospitalized for resection of stage II or III rectal cancer (n = 2716). We used χ² tests to examine associations between race and 1) consultation with an oncologist and 2) receipt of adjuvant therapy. We then used logistic regression to analyze the influence of sociodemographic and clinical characteristics (age at diagnosis, sex, marital status, median income and education in area of residence, comorbidity, and cancer stage) on black-white differences in the receipt of adjuvant therapy. All statistical tests were two-sided. Results: There was no statistically significant difference between the 134 black patients and the 2582 white patients in the frequency of consultation with a medical oncologist (73.1% for blacks vs 74.9% for whites, difference = 1.8%, 95% confidence interval [CI] = >5.9% to 9.5%, P =. 64) or radiation oncologist (56.7% vs 64.8%, difference = 8.1%, 95% CI = >0.5% to 16.7%, P =. 06), but blacks were less likely than whites to consult with both a medical oncologist and a radiation oncologist (49.2% vs 58.8%, difference = 9.6%, 95% CI = 0.9% to 18.2%, P =. 03). Among patients who saw an oncologist, black patients were less likely than white patients to receive chemotherapy (54.1% vs 70.2%, difference = 16.1%, 95% CI = 6.0% to 26.2%, P =. 006), radiation therapy (73.7% vs 83.4%, difference = 9.7%, 95% CI = 0.4% to 19.8%, P =. 06), or both (60.6% vs 76.9%, difference = 16.3%, 95% CI = 4.3% to 28.3%, P =. 008). Patient and provider characteristics had minimal influence on the racial disparity in the use of adjuvant therapy. Conclusion: Racial differences in oncologist consultation rates do not explain disparities in the use of adjuvant treatment for rectal cancer. A better understanding of patient preferences, patient-provider interactions, and potential influences on provider decision making is necessary to develop strategies to increase the use of adjuvant treatment for rectal cancer among black patients.