Changes in site distribution of colorectal carcinoma in Connecticut, 1940-1973.

The proportion of colorectal cancer occurring above the rectosigmoid junction has been increasing over time. The 40,771 cases of colorectal carcinoma reported to the Connecticut Tumor Registry from 1940 through 1973 were analyzed to determine the incidence in the ascending colon, the transverse, descending, and sigmoid colon, and the rectum. The numbers of cases, the proportion, and incidence rates of cancer in the ascending colon and sigmoid have increased over the 34 years. The increases were greatest among people over 65 years old. Only about half of colorectal cancer can now be identified with the rigid sigmoidoscope. Other tests must be used for early diagnosis of the increased numbers of cancers in the upper parts of the colon.