Assessment of a Staging System for Sigmoid Colon Cancer Based on Tumor Deposits and Extramural Venous Invasion on Computed Tomography

Abstract

Importance: Preoperative TNM stratification of colon cancer on computed tomography (CT) does not identify patients who are at high risk of recurrence that could be selected for preoperative treatment.

Objective: To evaluate the utility of CT findings for prognosis of sigmoid colon cancer.

Design, setting, and participants: This prognostic study used retrospective data from patients who underwent bowel resection for sigmoid colon cancer between January 1, 2006, and January 1, 2015, at a tertiary care center receiving international and national referrals for colorectal cancer. Statistical analysis was performed in April 2019.

Main outcomes and measures: Cox proportional hazards regression analysis was performed to investigate CT findings associated with disease recurrence. Kaplan-Meier survival plots were calculated for disease-free survival using CT staging systems.

Results: Of the 414 patients who had sigmoid colon cancer (248 [60.0%] men; mean [SD] age, 66.1 [12.7] years), with median follow-up of 61 months (interquartile range, 40-87 months), 122 patients (29.5%) developed disease recurrence. On multivariate analysis, nodal disease was not associated with disease recurrence; only tumor deposits (hazard ratio [HR], 1.90; 95% CI, 1.21-2.98; P = .006) and extramural venous invasion (HR, 1.97; 95% CI, 1.26-3.06; P = .003) on CT were associated with disease recurrence. Significant differences in disease-free survival were found using CT-T3 substage classification (HR, 1.88; 95% CI, 1.32-2.68) but not CT-TNM (HR, 1.55; 95% CI, 0.94-2.55). The presence of tumor deposits or extramural venous invasion on CT (HR, 2.45; 95% CI, 1.68-3.56) had the strongest association with poor outcome.

Conclusions and relevance: In this study, T3 substaging and detection of tumor deposits or extramural venous invasion on preoperative CT scans of sigmoid colon cancer were prognostic factors for disease-free survival, whereas TNM and nodal staging on CT had no prognostic value. T3 substaging and detection of tumor deposits or extramural venous invasion of sigmoid colon cancer was superior to TNM on CT and could be used to preoperatively identify patients at high risk of recurrence.

Figure 1.. Kaplan-Meier Curves for Tumor Recurrence Using Different Staging Systems

CT indicates computed tomography; TDV, tumor deposits and extramural venous invasion.

Figure 2.. Kaplan-Meier Curves for Recurrence on Subclassification of T and N Stage on Computed Tomography

T3 substage indicates T3a-T3b vs T3c-T3d category; TD, tumor deposit.

Figure 3.. T Stage, N Stage, and Extramural Venous Invasion on Computed Tomography

A, T3b tumor (within circle) shows 1- to 5-mm extramural spread; T3c tumor (inset) shows >5- to 15-mm extramural spread. B, Extramural venous invasion (arrowheads) from a tumor along the length of a vein. C, Enlarged lymph node (circle in left image) vs discontinuous tumor deposits (circle and arrowhead in right image) along the course of a vein.