Time trends in distal colorectal cancer subsite location related to age and how it affects choice of screening modality

Background and Objectives: A time trend analysis of colorectal cancer (CRC) incidence in the distal colorectum as a proportion of total CRC is present ed for the period 1977-1994 as a function of age, to determine the age at w hich Americans might best be served by screening fiberoptic sigmoidoscopy. Methods: CRC incidence rates were obtained for each anatomic subsite from S EER Public Use Files for 1977, 1986, and 1994. The colorectum was divided a natomically for these analyses at the junction of the descending colon and sigmoid colon. Incidence in the distal colorectum was divided by total CRC incidence to determine the proportion of CRC in that age/race/gender/year c ohort located in the distal colorectum. Results: The proportion of distal CRC among African Americans was without a clear trend as they grew older in each of the years of observation and in both genders. However, in whites, with increasing age, the proportion of di stal disease declined progressively in both genders, with the greatest decl ine in 1994. Distal CRC became less prevalent than proximal at about age 72 years in white women and at age 82 in white men in 1994. Conclusions: As the white population becomes older, and for African America ns of all ages, more total colon screening modalities an needed, although a t the onset of recommended screening, among 50- to 60-year-olds, fiberoptic sigmoidoscopy would appear efficacious. (C) 1998 Wiley-Liss, Inc.