Incidence trends for colorectal cancer in California: implications for current screening practices

The sensitivities of different screening methods for precancerous adenomas may affect the anatomical distribution of colorectal cancers. We used statewide data from California to describe time trends in the distribution of colorectal carcinoma.

Between 1988 and 1996, 110,378 cases of colorectal cancer were recorded in the California Cancer Registry database. Tumors proximal to, but not including, the sigmoid colon were termed "right-sided." The remaining tumors, excluding the anus, were termed "left-sided." Multivariable analyses were used to determine the effects of age, sex, and race on changes in tumor location over time.

During the study period, the annual incidence of colorectal cancer decreased steadily, from 200 to 162 cases per 100,000 residents. The decrease in left-sided tumors was about twice that observed on the right (-24.3% vs -11.6%). This disparity remained significant when adjusted for age, sex, and race (P = 0.0001).

The incidence of colorectal cancer in California is decreasing, particularly for left-sided (distal) tumors. Current screening recommendations, which emphasize examination of the distal colon, may need to be expanded to include the entire colon.