Is 10 Years Too Long? Development of Interval Colorectal Cancer Despite Following Recommended Colonoscopic Guidelines

Eric M Changchien, MD, Melinda Hawkins, MD, Michelle E Murday, MD, John A Griffin, MD. St Mark’s Hospital, Salt Lake City, Ut.

Background: Colorectal cancer is a leading cause of cancer mortality. Screening protocols have led to decreases in the incidence of colorectal cancer. Currently, average-risk individuals are recommended to undergo colonoscopy every 10 years starting at age 50. This recommendation has been based on the hypothesis that polyps have a growth rate of 0.5 cm in 2-5 years, while cancer develops from polyps in approximately 7-10 years. However, lesions are estimated to be missed 5% of the time. We have observed a number of patients who presented with colorectal cancer despite following established guidelines after screening colonoscopy. Our aim is to quantify the number of patients who develop colorectal cancer or high-grade dysplasia in the interval period between their prior colonoscopy and recommended follow-up screening exam.

Methods: A retrospective review of all patients with colorectal adenocarcinoma or high-grade dysplasia referred to two colorectal surgeons from October 2007 through September 2012 were included in our study. Exclusion criteria included patients at higher risk of developing colorectal cancer such as those with inflammatory bowel disease, familial polyposis, hereditary non-polyposis colorectal cancer or familial risk factors. Current colonoscopic guidelines were used to identify those patients who developed interim cancer despite following recommendations.

Results: Of 287 patients with colorectal cancer, 46 (16%) patients developed interval colorectal cancer despite undergoing screening colonoscopy and following recommended colonoscopic guidelines. Aside from 1 transverse colon cancer, distribution was otherwise relatively uniform: right colon 18, left colon 12, and rectum 15. Mean time from screening colonoscopy to diagnosis of cancer was 4.5 years. 32 of 46 (70%) cancers were discovered in 5 or fewer years.

Conclusions: 16% of patients presenting with colorectal cancer or high-grade dysplasia in our practice followed appropriate screening recommendations, with the majority of lesions discovered within 5 years. Our findings indicate that current screening recommendations for average-risk individuals may need to be re-examined.

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