Background & aims: Increasing evidence indicates that inherited susceptibility is important in the pathogenesis of colorectal neoplasia. The aim of this study was to clarify whether having only one first-degree relative with colorectal cancer increases the risk of developing adenomatous polyps and whether total colonoscopy is an appropriate screening measure in these patients.
Methods: The frequency of such a history was evaluated in 397 asymptomatic patients who underwent total colonoscopy. Of these patients, 155 had colorectal polyps and the remaining 242 did not have polyps.
Results: Among polyp cases, 27 of 155 (17.4%) had a positive history; among those without polyps, 12 of 242 (5.0%) had a positive history. Alternatively expressed, 27 of 39 patients (69%) with family history and 128 of 358 patients (36%) without family history had adenomas. The estimated risk for polyps associated with family history was 1.9. Among polyp cases, 14 of 27 patients (51.9%) with family history and 32 of 128 patients (25.0%) without family history had only proximal polyps (chi 2 test; P = 0.006; odds ratio, 3.2), In the same groups, frequency of high-grade dysplasia was 8 of 27 patients (29.6%) and 16 of 128 patients (12.5%), respectively (chi 2 test; P = 0.04; odds ratio, 2.9).
Conclusions: Relative to subjects with no family history, asymptomatic patients with one first-degree relative with colorectal cancer had nearly double the risk of developing adenomatous polyps, greater frequency of severely dysplastic lesions, and significantly higher frequency of proximal polyp location. This suggests that total colonoscopy screening is indicated in these subjects.