Changing patterns of colorectal carcinoma

Abstract

Over the 40 years 1928-1967, 5,807 surgical specimens of large bowel adenocarcinoma treated by resection were accumulated. These specimens were analyzed for maximum tumor diameter, incidence of lymph node metastases, location within the large bowel, and compared by decade. During this 40-year period, several trends in clinical presentation of disease were noted. Comparing the first to the last decade, the incidence of right colon cancer increased significantly from 7% to 22% of cases, while the relative incidence of sigmoid, rectosigmoid, and rectal carcinomas fell significantly from 80% to 62%. The size of the increasingly frequent right colon cancers was unchanged in recent years, and the incidence of lymph node metastases was constant during the decades studied. In contrast, there was a significant trend toward earlier disease in the sigmoid, rectosigmcid, and rectal cancers, manifested by a statistically significant decrease in the size of the primary cancers, a significant increase to 65% in the frequency of cases without lymph node metastases, and a decrease, to 9%, of cases with metastases to more than three lymph nodes. These trends are explained by the early detection techniques of sigmoidoscopy and rectal examination in recent years, by the more aggressive treatment of polyps within the reach of the sigmoidoscope, and by the greater susceptibility of the right colon to cancer in recent decades.