Background: If effective cancer screening is more common in people with a family history of cancer, the relationship between family history and cancer incidence may become distorted.
Methods: To assess the impact of screening on the association between colorectal cancer family history and risk of colorectal cancer, we developed a model to simulate screening patterns in those with and without a family history.
Results: The introduction of screening reduces the apparent risk of colorectal cancer associated with family history in subsequent generations. This reduction becomes more pronounced as the difference in the uptake of screening between those with a family history and those without becomes larger.
Conclusion: A result of effective screening is that observed family history of colorectal cancer may no longer match inherited risk, and observed family history may fail to be a strong risk factor. This may have implications for exposure-disease relationships if screening is differentially associated with the exposure.
From the aPublic Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA; bCarbone Comprehensive Cancer Center, University of Wisconsin, Madison, WI; cDepartment of Epidemiology, School of Public Health, University of Washington, Seattle, WA; and dDepartment of Public Health Sciences, School of Public Health, University of Alberta, Edmonton, Alberta, Canada.
Submitted 15 July 2011; accepted 25 October 2011; posted online 17 January 2012.
Supported by the National Cancer Institute at the National Institutes of Health (grant numbers U24CA074794, T32CA009168, and R25CA94880), and by the Canadian Institutes of Health Research Operating Grant entitled “Statistical Methods for Epidemiological Investigations.” The authors reported no other financial interests related to this research.
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Correspondence: Polly A. Newcomb, Cancer Prevention Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, M4-B402, Seattle, WA 98109. E-mail: firstname.lastname@example.org.