A new method of endoscopic ultrasonography for determining lesion depth in early gastric cancer

Atsushi Mitsunaga¹, Tomoko Tagata¹, Tetsuya Hamano¹, Honami Teramoto¹, Izumi Shirato², Miho Shirato², Takayoshi Nishino^2
1Department of Endoscopy, ²Department of Gastroenterology, Tokyo Women's Medical University Yachiyo Medical Center, Yachiyo, Chiba, Japan

Purpose: Endoscopic submucosal dissection (ESD) is recommended for the treatment of early gastric cancer (EGC) diagnosed as differentiated adenocarcinoma <30 mm in diameter with depth of invasion into the submucosa ≤500 µm (ie, submucosal [SM] 1 cancer). It is therefore important to develop a method for the differential diagnosis of SM1 (invasion depth ≤500 µm) from SM2/3 cancers (invasion depth >500 µm), of which the latter cannot be treated with ESD. To aid in differential diagnosis, a prospective study was conducted to establish a new diagnostic method for more accurate differential diagnosis by measurement of lesion depth using endoscopic ultrasonography (EUS) as a preoperative diagnostic modality.
Patients and methods: The lesions of 92 EGC patients were examined by EUS prior to ESD or surgery to identify and measure the area with the most thickened submucosal layer. A pathological examination of the entire resected lesion was conducted to diagnose depth of invasion and histological type of EGC. Using receiver operating characteristic analysis, a cut-off threshold of 2.2 mm for submucosal thickness was calculated for differential diagnosis of mucosal (M)-SM1 from SM2/3 cancers.
Results: By using thickness of the submucosal layer as measured by EUS and a cut-off threshold of 2.2 mm, M-SM1 could be distinguished from SM2/3 cancer with 98.6% accuracy, 93.2% sensitivity, and 94.7% specificity.
Conclusion: Using the thickness of the submucosal layer of an EGC lesion as determined by EUS and a cut-off threshold of 2.2 mm is a highly accurate means of differentiating M-SM1 from SM2/3 cancers when determining the best means of EGC treatment.

Keywords: adenocarcinoma, depth of invasion, early gastric cancer, endoscopic submucosal dissection, endoscopic ultrasonography, submucosal thickness