Background: Familial history of colorectal cancer (FHCRC) is a recognised risk factor for sporadic CRC. The relationship to the growth rate of adenomas is largely unknown. Lifestyle related factors, which may also cluster in families, are also recognised risk factors for adenomas and CRC.
Aims: To study the relationships between FHCRC and family history of other cancers (FHOC) among first degree relatives in relation to occurrence, growth, and recurrence of adenomas.
Patients and methods: Eighty seven patients with adenomas, participating in a double blind, three year, placebo controlled, endoscopic follow up and intervention study of growth and recurrence of polyps (50% men, 50-76 years). Polyps >9 mm were removed whereas the remainder and newly discovered polyps <10 mm were left in situ for three years before removal and histological diagnosis. Data were collected by means of dietary records, interviews, and questionnaires.
Results: The adenoma cases with FHCRC had a fourfold higher risk of adenoma growth. In contrast, no significant association was found for adenoma recurrence. FHOC was not significantly related to increased risk of growth or recurrence. Family history showed no significant association with the risk of baseline adenoma occurrence. Adjustment for CRC risk factors, also known to cluster in families, did not alter the results.
Conclusions: FHCRC seems to be a strong risk factor for adenoma growth, but not for the earlier phases of CRC development such as the initiation of adenomas.