Postcolonoscopy Colorectal Cancer in Sweden From 2003 to 2012: Survival, Tumor Characteristics, and Risk Factors.

BACKGROUND & AIMS: The rate of postcolonoscopy colorectal cancer (PCCRC) is a measure of colonoscopy quality, but there are conflicting results from studies of survival times of patients with PCCRC. We assessed survival times of patients with PCCRC and characterized the microscopic and macroscopic features of postcolonoscopy colorectal tumors.

METHODS

We performed a population-based cohort study using data from a database in Sweden, on 458,937 colonoscopies (54.0% women) performed from 2003 through 2012. Rates of colorectal cancer within 3 years of a colonoscopy were calculated based on the World Endoscopy Organization guidelines. Risk factors were evaluated using Poisson regression analysis. We used Cox regression models and Kaplan-Meier analyses, stratified by sex, to assess conditional survival. Logistic regression models were used to evaluate features of postcolonoscopy colorectal tumors, including stage location (right, left, or rectum) differentiation grade (high or low), synchronous tumors, perineural growth, resection margins, and mucinous and vessel characteristics.

RESULTS

Within 36 months after a colonoscopy, there were 19,184 individuals who had received a diagnosis of CRC; 1384 of these were PCCRCs (7.2%). The proportion of individuals with PCCRC decreased from 9.4% in 2003 to 6.1% in 2012. The largest risk factors for PCCRC were a prior diagnosis of CRC (relative risk [RR], 3.31; 95% CI, 2.71-4.04), ulcerative colitis (RR, 5.44; 95% CI, 4.75-6.23), Crohn's disease (RR, 3.81; 95% CI, 2.98-4.87), and prior polypectomy (RR, 2.32; 95% CI, 1.97-2.72). Individuals with PCCRCs had shorter survival times than individuals with CRCs detected during the index colonoscopy. Multivariate hazard ratios for PCCRC were 2.75 for men (95% CI, 2.21-3.42) and 2.00 for women (95% CI, 1.59-2.52), respectively. Individuals with left-side PCCRC had shorter survival times than patients with CRC detected during the index colonoscopy. Postcolonoscopy colorectal tumors had increased odds of low differentiation grade (odds ratio, 1.27; 95% CI, 1.09-1.49) compared with colorectal tumors detected during the index colonoscopy.

CONCLUSIONS

In an analysis of colonoscopies in Sweden, the rate of PCCRCs decreased from 9.4% in 2003 to 6.1% in 2012. Diseases that require surveillance (such as prior colorectal neoplasms and inflammatory bowel diseases) are the largest risk factors for PCCRC. Patients with PCCRC have shorter survival times than patients with CRC detected during their initial colonoscopy-especially women and patients with left-side tumors.