A randomized, controlled trial to assess a novel colorectal cancer screening strategy: the conversion strategy--a comparison of sequential sigmoidoscopy and colonoscopy with immediate conversion from sigmoidoscopy to colonoscopy in patients with an abnormal screening sigmoidoscopy.

OBJECTIVE Our study was a randomized, controlled trial to assess a novel strategy that provides comprehensive colorectal cancer screening in a single visit versus traditional sigmoidoscopy and, where appropriate, colonoscopy on a subsequent day. METHODS Consecutive patients referred for screening were randomized to control or so-called "conversion" groups. Patients in the control group were prepared for sigmoidoscopy with oral phospho-soda. Those with an abnormal sigmoidoscopy were scheduled for colonoscopy on a future day after oral polyethylene glycol preparation. In the conversion group, patients were prepared with oral phosphosoda. Patients with a polyp >5 mm or multiple diminutive polyps were converted from sigmoidoscopy to colonoscopy, allowing comprehensive screening in a single visit. Clinical outcomes were assessed by postprocedure physician and patient questionnaires. RESULTS Two hundred thirty-five patients were randomized (control = 121, conversion = 114). In the control group, 28% had an indication for colonoscopy. Three of 33 (9%) with an abnormal sigmoidoscopy did not return for colonoscopy. At colonoscopy, 27% had a proximal adenoma. In the conversion group, 28% had an abnormal sigmoidoscopy and underwent conversion to colonoscopy. Forty-one percent undergoing colonoscopy in the conversion group had a proximal adenoma. Physicians reported no differences in preparation or procedure difficulty, whereas patients reported no differences in the level of comfort or overall satisfaction between groups. When queried regarding preferences for future screening, 96% chose the conversion strategy. CONCLUSIONS The conversion strategy led to similar outcomes compared to traditional screening while improving compliance with colonoscopy in patients with an abnormal sigmoidoscopy.