Radiologist performance in differentiating polypoid early from advanced gastric cancer using specific CT criteria: emphasis on dimpling sign.

OBJECTIVE

The purpose of this study was to retrospectively determine whether there are specific CT features that can be used to differentiate polypoid early from advanced gastric cancer and to assess the performance of radiologists using specific CT findings for differentiation.

MATERIALS AND METHODS

A review of medical records yielded the cases of 46 patients, 27 with polypoid early gastric cancer and 19 with polypoid advanced gastric cancer, whose CT scans were available for review. Two radiologists retrospectively reviewed the CT images for the presence and depth of dimpling at the tumor base, the presence of vessel invagination at the dimpling site, thickening of the low-attenuating outer layer, perigastric infiltration, and transmural full-thickness enhancement of the lesion. Individual CT findings relevant as predictors were determined with univariate and multivariate analyses. Individual review of CT scans subsequently was performed by two other radiologists, who were blinded to tumor stage but aware of the results of univariate and multivariate analyses. Individual performance was evaluated with receiver operating characteristic analysis.

RESULTS

The presence of severe dimpling greater than 3.5 mm at the base of the tumor (odds ratio, 31.3) had the highest odds ratio for differentiating early from advanced gastric cancer, followed by vessel invagination (odds ratio, 12.3), the presence of dimpling (odds ratio, 9.8), perigastric infiltration (odds ratio, 5.2), and transmural full-thickness enhancement (odds ratio, 4.8). Multivariate analysis showed that the presence of dimpling greater than 3.5 mm was the only independent variable that differentiated polypoid advanced gastric cancer from polypoid early gastric cancer (p = 0.001). Subsequent differentiation of advanced from early gastric cancer with the described CT findings was very good, yielding areas under the receiver operating characteristic analysis curves of 0.827 and 0.811 for the two observers.

CONCLUSION

Greater than 3.5 mm dimpling and other ancillary CT findings are helpful in differentiating polypoid advanced gastric cancer from polypoid early gastric cancer and contribute to good individual accuracy for differentiation.