Originally published as JCO Early Release 10.1200/JCO.2008.18.6940 on July 20 2009

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Colorectal Cancer Risk Perception on the Basis of Genetic Test Results in Individuals at Risk for Lynch Syndrome

From the Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital; Harvard Medical School; Dana-Farber Cancer Institute; Division of Gastroenterology, Department of Medicine, Massachusetts General Hospital, Boston, MA; Division of Gastroenterology, Department of Medicine, University of Michigan, Ann Arbor, MI; Division of Gastroenterology, Department of Medicine, University of California San Francisco, San Francisco, CA; and the High Risk Cancer Clinics, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT.

Corresponding author: Sapna Syngal, MD, MPH, Dana-Farber Cancer Institute, 44 Binney St, Smith 209, Boston, MA 02114; e-mail: ssyngal{at}partners.org.

Purpose Lynch syndrome is associated with inherited germline mutations in mismatch repair (MMR) genes. Genetic testing in high-risk individuals may yield indeterminate results if no mutation is found or if a mutation of unclear pathogenic significance is observed. There are limited data regarding how well patients with Lynch syndrome understand the clinical implications of genetic test results. This study examines colorectal cancer (CRC) risk perception in individuals tested for MMR mutations and identifies the factors associated with an appropriate interpretation of their cancer risk.

Patients and Methods A total of 159 individuals who met the Revised Bethesda Guidelines and had previously undergone genetic testing completed a questionnaire eliciting demographic data, cancer history, genetic test results, and an estimate of their CRC risk. Associations between clinical factors, genetic test results, and CRC risk perception were explored using multivariable analyses.

Results Of the 100 individuals with a pathogenic mutation (true positive), 90 (90%) correctly estimated their CRC risk as "high" or "very high" compared with other individuals their age. However, only 23 (62%) of 37 individuals with an indeterminate genetic test result correctly estimated their risk. Individuals with a history of Lynch syndrome–associated cancer (odds ratio [OR], 0.1; 95% CI, 0.1 to 0.6) or indeterminate genetic test results (OR, 0.2; 95% CI, 0.1 to 0.6) were significantly less likely to estimate their CRC risk as increased.

Conclusion Patients at risk for Lynch syndrome with an indeterminate genetic test result may be falsely reassured. It is important that health care providers continue to discuss the implications of uninformative results on lifetime cancer risk.

Supported in part by Grants No. K24 CA113433 (S.S.) and K07 CA120448-01-A1 (E.M.S.) from the National Cancer Institute.

Presented at the 107th Annual Meeting of the American Gastroenterological Association Institute, May 20-25, 2006, Los Angeles, CA.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

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