Prevalence and Phenotypes of APC and MUTYH Mutations in Patients With Multiple Colorectal Adenomas

Shilpa Grover, MD, MPH; Fay Kastrinos, MD, MPH; Ewout W. Steyerberg, PhD; E. Francis Cook, ScD; Akriti Dewanwala, MD; Lynn Anne Burbidge, BS; Richard J. Wenstrup, MD; Sapna Syngal, MD, MPH

[+] Author Affiliations

Author Affiliations: Division of Gastroenterology, Brigham and Women's Hospital, Boston, Massachusetts (Drs Grover and Syngal); Harvard Medical School (Drs Grover and Syngal) and Harvard School of Public Health (Dr Cook), Boston; Population Sciences Division, Dana-Farber Cancer Institute, Boston (Drs Grover, Dewanwala, and Syngal); Program in Cancer Outcomes Research Training, Massachusetts General Hospital, Boston (Dr Grover); Columbia University Medical Center, New York, New York (Dr Kastrinos); Herbert Irving Comprehensive Cancer Center, New York, New York (Dr Kastrinos); Center for Medical Decision Making, Erasmus Medical Center, Rotterdam, the Netherlands (Dr Steyerberg); and Myriad Genetic Laboratories Inc, Salt Lake City, Utah (Ms Burbidge and Dr Wenstrup).

JAMA. 2012;308(5):485-492. doi:10.1001/jama.2012.8780

Context Patients with multiple colorectal adenomas may carry germline mutations in the APC or MUTYH genes.
Objectives To determine the prevalence of pathogenic APC and MUTYH mutations in patients with multiple colorectal adenomas who had undergone genetic testing and to compare the prevalence and clinical characteristics of APC and MUTYH mutation carriers.
Design, Setting, and Participants Cross-sectional study conducted among 8676 individuals who had undergone full gene sequencing and large rearrangement analysis of the APC gene and targeted sequence analysis for the 2 most common MUTYH mutations (Y179C and G396D) between 2004 and 2011. Individuals with either mutation underwent full MUTYH gene sequencing. APC and MUTYH mutation prevalence was evaluated by polyp burden; the clinical characteristics associated with a pathogenic mutation were evaluated using logistic regression analyses.
Main Outcome Measure Prevalence of pathogenic mutations in APC and MUTYH genes.
Results Colorectal adenomas were reported in 7225 individuals; 1457 with classic polyposis (≥100 adenomas) and 3253 with attenuated polyposis (20-99 adenomas). The prevalence of pathogenic APC and biallelic MUTYH mutations was 95 of 119 (80% [95% CI, 71%-87%]) and 2 of 119 (2% [95% CI, 0.2%-6%]), respectively, among individuals with 1000 or more adenomas, 756 of 1338 (56% [95% CI, 54%-59%]) and 94 of 1338 (7% [95% CI, 6%-8%]) among those with 100 to 999 adenomas, 326 of 3253 (10% [95% CI, 9%-11%]) and 233 of 3253 (7% [95% CI, 6%-8%]) among those with 20 to 99 adenomas, and 50 of 970 (5% [95% CI, 4%-7%]) and 37 of 970 (4% [95% CI, 3%-5%]) among those with 10 to 19 adenomas. Adenoma count was strongly associated with a pathogenic mutation in multivariable analyses.
Conclusions Among patients with multiple colorectal adenomas, pathogenic APC and MUTYH mutation prevalence varied considerably by adenoma count, including within those with a classic polyposis phenotype. APC mutations predominated in patients with classic polyposis, whereas prevalence of APC and MUTYH mutations was similar in attenuated polyposis. These findings require external validation.