Improving the ascertainment of families at high risk of colorectal cancer: a prospective GP register study.

Abstract

BACKGROUND: Screening for colorectal cancer is effective in family members with a high risk of this condition, owing to single gene mutations. However, it is not known which is the most effective method of ascertaining these families at high risk. AIMS: To investigate whether a case-finding approach using computerised general practitioner (GP) registers would improve the ascertainment of families at high risk of colorectal cancer due to family history. DESIGN OF STUDY: Prospective GP register study. SETTING: General practices in Oxfordshire. METHOD: Identification of patients with colorectal cancer using GP registers, followed by a family history questionnaire survey to identify those at high risk. RESULTS: Using GP registers, 758 patients with a diagnosis of colorectal cancer were identified; a prevalence of 172 cases per 100 000 (95% confidence interval = 159 to 184). Of these, 305 patients, diagnosed under the age of 65 years, were sent a family history questionnaire. Two hundred and one (66%) patients responded to the survey; 10 (5%) patients were assessed as having high-risk families and 47 (23%) patients were assessed as having families at moderate risk. Eight of the high-risk patients had 34 first degree relatives who would benefit from routine disease surveillance, and 37 moderate-risk patients had 153 first degree relatives. Only two high-risk and six moderate-risk patients identified were previously known to the local Clinical Genetics Department. CONCLUSION: A case-finding approach using GP records and a family history questionnaire is an effective way of identifying families at high risk of developing colorectal cancer, who can then be offered disease surveillance.