Risk Stratification for Advanced Proximal Colon Neoplasm and Individualized Endoscopic Screening for Colorectal Cancer by a Risk-scoring Model

Background: Only 30% to 40% of patients with advanced proximal neoplasms (APN) have distal colon neoplasms.

Objective: To develop a risk score model for APN and propose an individualized screening protocol for colorectal cancer.

Design: Retrospective cohort study.

Setting: Tertiary-care center.

Patients: Derivation cohort (6200 adults) and validation cohort (1389 adults).

Intervention: Screening colonoscopy.

Main Outcome Measurements: An APN risk score model was developed from the derivation cohort (6200 adults) and was tested in the validation cohort (1389 adults), who underwent screening colonoscopy.

Results: Age, male sex, and smoking were clinical risk factors for APN. The presence of a distal neoplasm was a sigmoidoscopic risk factor for APN. We calculated APN risk scores (0-8) based on these variables and classified patients as low risk (0-2) or high risk (3-8). In the validation cohort, the relative risk of APN was 3.5-fold higher in the high-risk group than in the low-risk group. Our model suggests that colonoscopy should be performed as an initial screening test in patients with a high clinical risk for APN. Sigmoidoscopy should be performed initially in patients with low clinical risk for APN followed by supplementary colonoscopy in those with high APN risk scores based on both clinical and sigmoidoscopic risk factors. This protocol detected APN in 22 of 34 APN+ patients (64.7%) with little increase in the endoscopy burden, whereas only 16 of 34 APN+ patients (47.1%) would be identified by initial sigmoidoscopy followed by colonoscopy only in cases with distal neoplasms.

Limitations: Retrospective design.

Conclusion: Our APN risk score model provides an algorithm for efficient screening of colorectal cancer by sigmoidoscopy and colonoscopy.