Diabetes Mellitus and Subsite-Specific Colorectal Cancer Risks in the Iowa Women's Health Study

To the Editors: In the Iowa Women's Health Study, Limburg et al. ([1][1]) found that diabetes increased the risk of cancer of the proximal colon (relative risk = 1.4), but not that of the distal colon (relative risk = 1.1) or the rectum (relative risk = 0.8). Epidemiologic evidence on the subsite-