Interval Colorectal Cancers at Ochsner Medical Center: Where Do We Stand?

BACKGROUND: An interval colorectal cancer is a cancer diagnosed prior to the recommended follow-up time from a previously negative colonoscopy. These cancers are thought to arise from a rapidly growing cancer, missed cancer, or incompletely resected adenomas. Our study aimed to identify interval cancers diagnosed during a 4-year period and to identify any potential risk factors associated with these cancers. Secondly, we compared our interval colorectal cancer rate with other published rates. METHODS: Our population included all patients who underwent colonoscopy for any indication between August 1, 2010 and July 31, 2014 (n=28,794), excluding individuals <18 years and patients with a history of inflammatory bowel disease, previously diagnosed colorectal cancer, or known hereditary cancer syndrome. Using a retrospective review of our institution's electronic medical record and data from the Louisiana Tumor Registry, we identified patients who were diagnosed with colorectal cancer. From these individuals, we reviewed and selected those who met the criteria for interval cancers. RESULTS: We identified 20 interval cancers during the 4-year study period. Based on the total number of index colonoscopies performed during the time period, our overall incidence rate was 0.07%. Approximately 1 interval cancer was diagnosed per 1,400 colonoscopy examinations. Our occurrence rate of 0.28 cases per 1,000 person-years of observation was less than or similar to the rates reported in other studies. CONCLUSION: Our study demonstrated that our institution has a low incidence of interval cancers, supporting the effectiveness of our cancer screening program. To further minimize interval colorectal cancers, we recommend the documentation and reporting of endoscopy quality measures, as well as close follow-up intervals or alternate examinations for patients who have poor bowel preparation or incomplete/difficult examinations.