Risk of Advanced Adenomas in Siblings of Individuals With Advanced Adenomas: A Cross-Sectional Study.

BACKGROUND & AIMS: The risk of colorectal neoplasms among siblings of patients with advanced adenomas is not clear. We determined the prevalence of advanced adenomas in the siblings of patients with advanced adenomas and compared it with that of siblings of individuals without these lesions.

METHODS: In a blinded, cross-sectional study, colonoscopies were performed (from 2010 through 2014), at 2 hospitals in Hong Kong on 200 asymptomatic siblings of patients with advanced adenomas (exposed; mean age, 58.2 ± 6.3 years; adenomas ≥10 mm, high-grade dysplasia, villous, or tubulovillous) and 400 age- and sex-matched siblings of subjects with normal findings from colonoscopies and no family history of colorectal cancer (unexposed; mean age, 58.1 ± 6 years). We recruited 1 sibling per family. The primary outcome was prevalence of advanced adenomas.

RESULTS: Baseline demographics (ie, aspirin use, smoking, body mass index, and metabolic diseases) did not differ significantly between exposed and unexposed individuals. The prevalence of advanced adenoma was 11.5% among the exposed subjects and 2.5% among the unexposed subjects (matched odds ratio [mOR] = 6.05; 95% confidence interval [CI]: 2.74-13.36; P < .001). The prevalence of adenomas ≥10 mm was higher among exposed than unexposed siblings (10.5% vs 1.8%; mOR = 8.59; 95% CI: 3.44-21.45; P < .001), as was the prevalence of villous adenomas (5.5% vs 1.3% in unexposed; mOR = 6.28; 95% CI: 2.02-19.53; P = .001) and all colorectal adenomas (39.0% vs 19.0% in unexposed; mOR = 3.29; 95% CI: 2.16-5.03; P < .001). Two cancers were detected in exposed siblings and none in unexposed siblings.

CONCLUSIONS: In a cross-sectional study of subjects undergoing colonoscopy in Hong Kong, siblings of individuals with at least 1 advanced adenoma had a 6-fold increased odds of advanced adenoma compared with subjects who had a sibling with a screening colonoscopy with no identified neoplasia. ClinicalTrials.gov, Number: NCT01593098.