# Quantitative Evaluation of the Invasion Depth of Colorectal Cancer Located on a Colorectal Fold Through the Width of Colorectal-Fold Lateral Contour Using a Lateral Split-View Computed Tomographic Air-Contrast Enema Image

## TL;DR

This study shows that measuring the width of a specific contour in CT images can help determine how deep colorectal cancer has invaded when it's located on a fold in the colon.

## Contribution

The first demonstration that quantifying the lateral contour width in CT enema images improves depth-of-invasion diagnosis for fold-located colorectal cancer.

## Key findings

- T1b/more deeply invading CRCs had significantly larger lateral contour widths (12.1 mm) than intramucosal/T1a CRCs (3.3 mm).
- A 6 mm cut-off value achieved 92.9% sensitivity and 87.5% specificity for differentiating invasion depths.
- High inter-rater reliability (intraclass correlation coefficient of 0.949) was observed for the measurements.

## Abstract

Purpose: The aim of the study was to investigate the usefulness of quantitatively evaluating the width of lateral contour on a lateral split-view computed tomographic air-contrast enema (CT enema) image to diagnose the invasion depth of colorectal cancer (CRC) located on a colorectal fold.

Methods: The cases of 22 patients with 22 fold-located CRCs, that is, 12 (54.5%) early CRCs and 10 (45.5%) advanced CRCs, who underwent a pretherapeutic CT colonography, were retrospectively examined. T1-stage CRCs were classified into two categories according to the Japanese guideline: T1a-stage (carcinoma invading the superficial submucosa (<1000 μm)) and T1b-stage (carcinoma invading the deeper submucosa (≧1000 μm)). The maximum width of colorectal-fold lateral contour on which the CRC was located, i.e., the gap distance between the two adjacent haustrations, was calculated from the lateral split-view CT enema image by three gastrointestinal radiologists. These values were compared between the intramucosal/T1a CRCs and the T1b/more deeply invading CRCs. The inter-rater intraclass correlation coefficients were also evaluated for reliability.

Results: The maximum widths of colorectal-fold lateral contour were significantly higher in the T1b/more deeply invading CRCs than in the intramucosal/T1a CRCs (3.3±1.4 mm and 12.1±4.6 mm, respectively; p<0.0001). The optimum cut-off value of the maximum width of colorectal-fold lateral contour for differentiating the former from the latter was 6 mm, with a sensitivity and specificity of 92.9% and 87.5%, respectively. The inter-rater intraclass correlation coefficient for the measurement of colorectal-fold lateral contour was 0.949.

Conclusions: We demonstrated for the first time that the quantitative evaluation of the width of the lateral contour using a lateral split-view CT enema image can improve the diagnostic accuracy of the invasion depth for CRCs located on a colorectal fold.