Background-A multicentre randomised controlled trial to evaluate scree
ning by ''once only'' flexible sigmoidoscopy (FS) for prevention of bo
wel cancer is in progress. Aims-To pilot the trial protocol examining
rates of attendance, yield of neoplasia, and adverse effects. Subjects
-A total of 3540 subjects aged 55-64 years in Welwyn Garden City (WGC)
and 19 706 in Leicester (LE). Methods-Subjects responding positively
to an ''interest in screening'' questionnaire were randomised to invit
ation for screening or control arms, Small polyps were removed during
screening, Colonoscopy was undertaken for high risk polyps (more than
two adenomas, size at least I cm, villous histology, severe dysplasia,
or malignancy). The remainder were discharged. Results-In WGC and LE
respectively, 59% and 61% indicated an interest in screening, of which
74% and 75% attended. Adenomas were detected in 10% and 9%, respectiv
ely, and cancers in 7 per 1000 (in both centres), 55% at Dukes's stage
A. The colonoscopy referral rate was 6% in both centres, Mild, short
lived bleeding occurred in 3%, One person died following surgery. Conc
lusions-Compliance rates, yield of adenomas, and referral rate for col
onoscopy were as expected, but cancer detection rates were higher. Adv
erse effects following sigmoidoscopy or colonoscopy were mild and tran
sient, but there was one postoperative death, A randomised trial is ne
cessary to evaluate fully the risks and benefits of this intervention.