The frequency of a positive family history for colorectal cancer: a population-based study in the Netherlands.

Background: Subjects with a positive family history of colorectal cancer (CRC) have an increased risk of developing CRC themselves. This risk depends on the number of affected relatives and the age at diagnosis. Aim: The aim of this study was to assess the prevalence of a positive family history of CRC, within a random cohort among the Dutch population. Methods: A total of 5072 subjects aged between 45 and 70 years were invited to fill in an anonymous questionnaire about the occurrence of CRC in their first-degree relatives (FDR). Results: The questionnaire was returned by 3973 subjects (78.3%). Thirty responders (0.8%) had CRC themselves. Of all unaffected responders, 44I (11.2%) subjects reported a positive family history of CRC. Ninety (2.3%) responders reported having an FDR with CRC diagnosed before the age of 50, or reported two or more FDRs with CRC. Conclusion: The prevalence of a positive family history of CRC is substantial. Identification of this high-risk group by obtaining a thorough family history is the first step in targeting preventive measures.