Outcome of follow-up colon examination among a population-based cohort of colorectal cancer patients.

BACKGROUND & AIMS: The benefit of colonoscopy in the follow-up of colorectal cancer survivors is uncertain, and findings of surveillance colonoscopy are not well-characterized. We sought to estimate survival among colorectal cancer patients according to receipt of a follow-up colon examination and to describe the findings of such exams.

METHODS: We studied health maintenance organization enrollees with colorectal cancer who underwent surgical resection. Mortality was estimated by using survival analysis, and findings of colon examinations were determined by review of pathology reports.

RESULTS: One thousand two patients were eligible for study; 5-year survival was higher (76.8%) for patients who had at least one follow-up exam than for patients who did not undergo follow-up (52.2%, P < .0001). In multivariate analysis, colon examination remained independently associated with improved survival (hazard ratio, 0.58; 95% confidence interval, 0.44-0.75). Twenty patients (3.1%) were diagnosed with a second colorectal cancer, including 9 cancers detected within 18 months of initial cancer diagnosis. Advanced neoplasia was more common (15.5%) among patients followed up between 36-60 months after diagnosis compared with patients followed up within 18 months (6.9%, P = .02). History of adenomas was associated with advanced neoplasia on follow-up (P = .002). Patients with advanced neoplasia on initial follow-up were at high risk for advanced neoplasia on subsequent examinations (13/16, 81%).

CONCLUSIONS: After colorectal cancer resection, patients have a high risk of interval cancers, some of which represent missed lesions at initial diagnosis. Therefore, surveillance colonoscopy within 1 year of initial diagnosis is warranted. After adjusting for key variables, endoscopic surveillance is associated with improved survival.