Epidemiology and familial risk of synchronous and metachronous colorectal cancer: a population-based study in Utah.

BACKGROUND & AIMS Patients diagnosed with colorectal cancer (CRC) are at risk for synchronous and metachronous lesions at the time of diagnosis or during follow-up evaluation. We performed a population-based study to evaluate the rate, predictors, and familial risk for synchronous and metachronous CRC in Utah. METHODS All newly diagnosed cases of CRC between 1980 and 2010 were obtained from the Utah Cancer Registry and linked to pedigrees from the Utah Population Database. RESULTS Of the 18,782 patients diagnosed with CRC, 134 were diagnosed with synchronous CRC (0.71%) and 300 were diagnosed with metachronous CRC (1.60%). The risk for synchronous CRC was significantly higher in men (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.02-2.06) and in patients aged 65 years or older (OR, 1.50; 95% CI, 1.02-2.21). Synchronous CRCs were located more often in the proximal colon (OR, 1.70; 95% CI, 1.20-2.41). First-degree relatives of cases with synchronous (OR, 1.86; 95% CI, 1.37-2.53), metachronous (OR, 2.34; 95% CI, 1.62-3.36), or solitary CRC (OR, 1.75; 95% CI, 1.63-1.88) were at increased risk for developing CRC, compared with relatives of CRC-free individuals. Four percent of first-degree relatives of patients with synchronous or metachronous cancer developed CRC at younger ages than the age recommended for initiating CRC screening (based on familial risk), and therefore would not have been screened. CONCLUSIONS Of patients diagnosed with CRC, 2.3% are found to have synchronous lesions or develop metachronous CRC during follow-up evaluation. Relatives of these patients have a greater risk of CRC than those without a family history of CRC. These results highlight the importance of obtaining a thorough family history and adhering strictly to surveillance guidelines during management of high-risk patients.