Diagnosis of early colorectal cancer invasion depth by quantitative evaluation of the basal indentation in CT colonography

Objective

To investigate the feasibility of diagnosing the invasion depth of early colorectal cancer (CRC) by quantitatively evaluating the basal indentation (BI)—i.e., the intestinal lateral deformity—in CT colonography (CTC).

Materials and methods

34 early CRCs (13 Tis CRCs and 21 T1 CRCs) in 32 patients who underwent a preoperative CTC were retrospectively examined. Two radiologists calculated the depth of the BI on a computed tomographic air-contrast enema (CT enema) image, the depth of the BI due to the geometric function (BI-G) on a cross-sectional multiplanar reconstruction (CS-MPR) image, and the ratio of the BI to the BI-G (i.e., the “BI ratio”) for each lesion. The BI ratios of the Tis and T1 CRCs were compared.

Results

The BI ratios were significantly higher in the T1 CRCs than in the Tis CRCs (p < 0.0001). The optimum cutoff value of the BI ratio for differentiating the T1 CRCs from the Tis CRCs was 1.64, with a sensitivity, specificity, and area under the curve of 90.5 %, 100 %, and 0.974, respectively.

Conclusions

We have demonstrated for the first time that quantitatively evaluating the BI can improve the accuracy of diagnosis of early CRC invasion depth.