Response: Re: Residual Treatment Disparities After Oncology Referral for Rectal Cancer

We appreciate the interest of Dr Field and colleagues in our recent article (1). The main objective of our study was to better understand mechanisms that underlie racial disparity in the receipt of adjuvant therapy for rectal cancer, including access to care. Using Surveillance, Epidemiology, and End Results–Medicare data, we found no statistically significant difference between black and white patients in the rates of consultation with an oncologist but a persistent and statistically significant difference in the rates of receipt of adjuvant therapy after consultation. A secondary finding was that racial disparities in receipt of care were greatest among patients with fewer comorbid diseases and those who tended to be younger.

Field and colleagues were concerned about our exclusion criteria and assumed that they limited the statistical power of our study. Overall, 54% of black patients were excluded and 41% of white patients were excluded. The difference in proportions was primarily due to racial differences in complete enrollment in Medicare parts A and B during the study and in the rates of resection. A limitation of such claims data is that little can be said about those who were not enrolled. The statistical power of the study is a nonissue, because our results were statistically significant. For example, analysis of the difference between white and blacks in the receipt of both chemotherapy and radiation therapy had a statistical power of 91.4%, which precludes the existence of a type II error.

Field and colleagues also assumed that our examination of incident cases for 1992–1999 may have limited relevance of the findings, noting that preoperative chemoradiation is now standard practice for advanced rectal cancer. Although such practice is no doubt desirable, we examined time trends in the use of radiation (2) and found that more than 30% of patients with stage III rectal cancer diagnosed in 2000 still did not receive pre- or postoperative radiation. Unlike Field and colleagues, we maintain that the year 2000 must be considered within the era of modern practice.

Finally, we congratulate Field and colleagues on their audit of their patients' receipt of adjuvant therapy for rectal cancer. They demonstrate that as patients age they are less likely to receive chemotherapy. Although this finding has nothing to do with racial disparities in receipt of chemotherapy, we concur. The majority of patients in our study were less likely to receive chemotherapy with increasing age. We look forward to a more comprehensive analysis of the data from Dr Field and colleagues in the future.