Introduction Surveillance colonoscopy and polypectomy in those with a family history of colorectal cancer (CRC) may prevent malignant transformation of adenomatous polyps yet would then attenuate the apparent strength of familial aggregation. This study compares UK and US surveillance recommendations and considers the effect of polypectomy on family history.

Methods We performed a ‘proof of principle’ study of patients undergoing colonoscopy for ‘family history’ and polypectomy for large adenomas (= > 1cm) at our trust over an 18-month period. UK and US Surveillance recommendations for a hypothetical first degree relative (FDR) of each patient were calculated. Surveillance recommendations for FDRs were re-calculated assuming that polypectomy had not been performed in our patients and CRC had developed.

Results 14 patients were included with median age 50 years. UK guidelines recommended no screening or once-off colonoscopy for 9/14 FDRs of our sample, while US guidelines recommended at least 5 yearly colonoscopy for all FDRs. The hypothetical development of CRC in our patients resulted in increased surveillance recommendations for 12/14 hypothetical FDRs under UK guidelines but for only 3/14 FDRs under US guidelines.

Conclusion In those with a family history of CRC, surveillance colonoscopy and polypectomy may attenuate the apparent level of risk to those patients’ first degree relatives. US guidelines, which consider CRC and advanced adenomatous polyps as equal familial risk factors, recommend more aggressive surveillance in the kindred of our study sample, yet may be considered excessive. Under UK guidelines CRC risk may be underestimated and recommended surveillance inadequate.

Disclosure of Interest None Declared.