Population-based colonoscopy screening for colorectal cancer: High participation rates are not affected by source of invitation

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BACKGROUND: Colunoscopic screening for colorectal cancer (CRC) may be the most costeffective strategy in yeats of life saved. The success of screening depends critically on high participation rates, and the best recruitment strategy has not been determined. Studies of populatiun-hased fecal occult blood testing have shown participation rates improved when invitation to screening comes from a family physician known to the patient (Hardeastle JD Lancet 1983;2:1-4). AIMS: (i) To compare response rates, positive response rates and participation rates of a random population sample and a Family Physician sample; (if) To determine tim proportion of respondents not eligible tbr or not requiting screening, thereby detenniniug a better estimate of the screening population size; (iii) To determine polyp prevalence in a sample of 250 colonoscopies. METHODS: In the first recruitment strategy, 1000 persons aged 55-74 were randomly selected from the state Electoral Register and crossrderenced against tim state Cancer Registry. hrvitations were mailed to 357 of these persons. In die second strategy, Family Pbysiclans from six geographical clusters selected 134 persons at random Written invitations were fhen co-signed by the investigators. Qnestionrtaires were administered to determine knowledge of CRC and colonoscopy, and quality of life, before attd alter colonoscopy RESULTS: As at December 2002, the overall response rate to written invitations were 61% (n = 80) and 59% (n = 218) from Electoral Register and Family Physician invitees respectively. The positive response rate was 46% in both strategies. Ninetytwo persons were ineligible with 64 having had colonoscopy in the previous ten years. One hundred and une colonoscopies have been performed with adenomatons polyps present in 27 subjects (27%); f:mr ot these subjects had advanced lesmns (15%). CONCLUSIONS: rfiese data show (i) l:'arncipation rates are not superior ve (if) Colonoscopy is a highly acceptable screening method to consumers; 0if) In centres ,*atb good access to care, the digible (tree screening) population may be much smaller than anticipated.