Prospective colonoscopic study to investigate risk of colorectal neoplasms in first-degree relatives of patients with non-advanced adenomas.

Objective The risk associated with a family history of non-advanced adenoma (non-AA) is unknown. We determined the prevalence of colorectal neoplasms in subjects who have a first-degree relative (FDR) with non-AA compared with subjects who do not have an FDR with adenomas. Design In a blinded, cross-sectional study, consecutive subjects with newly diagnosed non-AA were identified from our colonoscopy database. 414 FDRs of subjects with non-AA (known as exposed FDRs; mean age 55.0 +/- 8.1 years) and 414 age and sex-matched FDRs of subjects with normal findings from colonoscopy (known as unexposed FDRs; mean age 55.2 +/- 7.8 years) underwent a colonoscopy from November 2015 to June 2018. One FDR per family was recruited. FDRs with a family history of colorectal cancer were excluded. The primary outcome was prevalence of advanced adenoma (AA). Secondary outcomes included prevalence of all adenomas and cancer. Results The prevalence of AA was 3.9% in exposed FDRs and 2.4% in unexposed FDRs (matched OR (mOR)=1.67; 95% CI 0.72 to 3.91; p=0.238 adjusted for proband sex and proband age). Exposed FDRs had a higher prevalence of any adenomas (29.2% vs 18.6%; mOR=1.87; 95% CI 1.32 to 2.66; p<0.001) and non-AA (25.4% vs 16.2%; mOR=1.91; 95% CI 1.32 to 2.76; p=0.001). A higher proportion of exposed FDRs than unexposed FDRs (4.3% vs 2.2%; adjusted mOR=2.44; 95% CI 1.01 to 5.86; p=0.047) had multiple adenomas. No cancer was detected in both groups. Conclusion A positive family history of non-AA does not significantly increase the risk of clinically important colorectal neoplasia. The data support current guidelines which do not advocate earlier screening in individuals with a family history of non-AA.