Transabdominal Ultrasonography for Assessing the Depth of Tumor Invasion in Gastric Cancer

[Background] Although endoscopy and endoscopic ultrasonography are generally used to diagnose the depth of gastric tumor invasion, endoscopy is invasive and frequently results in patient discomfort. Transabdominal ultrasonography (TUS) is noninvasive and may be useful in determining this depth. We investigated the usefulness of TUS in determining the depth of tumor invasion in patients with gastric cancer. [Methods] This retrospective study included 190 patients with gastric cancer and 200 lesions who underwent curative resection at the Department of Gastrointestinal Surgery of Tottori University Hospital from July 2007 to July 2015. The results of conventional diagnostic imaging and TUS were compared with those of pathological analysis obtained after surgery. Furthermore, the ruptured form of the third layer on TUS imaging was reviewed and investigated to differentiate between the SM2 and MP lesions. [Results] The accuracy of TUS was similar to that of conventional diagnostic imaging for all depths of tumor invasion. Eight lesions could not be assessed by TUS, including four that could not be identified and four in which TUS was unable to diagnose the depth. In cases where the ruptured form of the third layer could be determined in MP lesions, the forms were observed toward the inside of the gastric lumen. [Conclusion] The results of this study suggested that the accuracy of TUS was equivalent to that of conventional diagnostic imaging in determining the depth of tumor invasion. TUS assessment criteria may be useful to classify this depth. Furthermore, the ruptured form of the third layer is believed to be important in distinguishing between early and advanced gastric cancer.