How to identify patients who are less likely to have metachronous neoplasms after a colon cancer: a predictive model

Background. Patients with prior colon cancer have increased risk of metachronous colorectal neoplasms; therefore, endoscopic surveillance is indicated. Current recommendations are not risk-stratified. We investigated predictive factors for colorectal neoplasms to build a model to spare colonoscopies for low-risk patients. Methods. This was a multicenter, retrospective study including patients who underwent surgery for colon cancer in 2001 – 2008 (derivation cohort) and 2009 – 2013 (validation cohort). A predictive model for neoplasm occurrence at second surveillance colonoscopy was developed and validated. Results. 421 and 203 patients were included in derivation and validation cohort, respectively. At second surveillance colonoscopy, 112 (26.6%) and 55 (27.1%) patients had metachronous neoplasms in derivation and validation groups; three cancers were detected in the latter. History of left-sided colon cancer (OR 1.64, 95 %CI 1.02 – 2.64), ≥1 advanced adenoma at index colonoscopy (OR 1.90, 95 %CI 1.05 – 3.43), and ≥ 1 adenoma at first surveillance colonoscopy (OR 2.06, 95 %CI 1.29 – 3.27) were independently predictive of metachronous colorectal neoplasms at second surveillance colonoscopy. For patients without such risk factors, diagnostic accuracy parameters were: 89.3% (95% CI 82.0 %-94.3%) and 78.2% (95 %CI 65.0%-88.2%) sensitivity, and 28.5% (95%CI 23.5%-33.9%) and 33.8% (95%CI 26.2%-42.0%) specificity in derivation and validation group, respectively. No cancer would be missed. Conclusions. Patients with prior left-sided colon cancer or ≥ 1 advanced adenoma at index colonoscopy or ≥1 adenoma at first surveillance colonoscopy had a significantly higher risk of neoplasms at second surveillance colonoscopy; patients without such factors had much lower risk and could safely skip the second surveillance colonoscopy. A prospective, multicenter validation study is needed.