title: Time trends in distal colorectal cancer subsite location related to age and how it affects choice of screening modality.
abstract: OBJECTIVE
  A time trend analysis of colorectal cancer (CRC) incidence in the distal colorectum as a proportion of total CRC is presented for the period 1977-1994 as a function of age, to determine the age at which Americans might best be served by screening fiberoptic sigmoidoscopy.
  
  
  METHODS
  CRC incidence rates were obtained for each anatomic subsite from SEER Public Use Files for 1977, 1986, and 1994. The colorectum was divided anatomically 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 cohort 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 distal disease declined progressively in both genders, with the greatest decline 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 Americans of all ages, more total colon screening modalities are needed, although at the onset of recommended screening, among 50- to 60-year-olds, fiberoptic sigmoidoscopy would appear efficacious.
authors.affiliation: Department of Surgery, University of Illinois College of Medicine, Chicago 60612, USA. altohorn@uic.edu
authors.forename: R L
authors.initials: RL
authors.lastname: Nelson
authors.forename: V
authors.initials: V
authors.lastname: Persky
authors.forename: M
authors.initials: M
authors.lastname: Turyk
mesh_terms: D000367:Age Factors; D000368:Aged; D003106:Colon / Q000473:pathology*; D012809:Colon, Sigmoid / Q000473:pathology; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000208:ethnology / Q000473:pathology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D044469:Racial Groups; D012007:Rectum / Q000473:pathology*; D018426:SEER Program; D012737:Sex Factors; D012812:Sigmoidoscopy