Therapeutic outcomes of endoscopic submucosal dissection of undifferentiated type intramucosal gastric cancer without ulceration and 20 mm or smaller in diameter preoperatively diagnosed

Background : With the advancement of endoscopic submucosal dissection (ESD) technology, early gastric cancer (EGC) is increasingly being treated endoscopically. It remains to be determined whether endoscopic treatment is indicated for undifferentiated type EGC. Because this type of cancer is highly likely to be associated with lymph node metastasis in addition to difficulty in preoperative assessment of the lesion size and invasion depth. Methods : We reviewed 58 patients with preoperatively diagnosed undifferentiated type intramucosal EGC without ulceration and diameter of 20mm or smaller (expanded-indication lesion) who underwent ESD at Cancer Institute Hospital in the period between September 2003 and August 2008. Results : The overall rates of en bloc resection and complete en bloc resection was 98%, 90% respectively, and the median operation time was 70 minutes. Bleeding was seen in 8.6% and perforation in 3.4% . The curative resection rate was low at 79% . Factors responsible for non-curative resection were most commonly submucosal invasions. If limited to pathologically diagnosed expanded-indication lesions, the curative resection rate was 98% . The difference in tumor size between a macroscopic diameter and a histrogic diameter was within ±5 mm in 96% of expanded-indication lesions, with none of these cases having a histologic diameter that exceeded the macroscopic diameter by more than 5 mm. Conclusion : ESD was technologically feasible for expanded-indication lesions of the undifferentiated type EGC. We achieved a high rate of curative resection by the markings at sites 5 mm beyond the preoperatively determined lesion area. Factors responsible for non-curative resection were most commonly submucosal invasions, we should diagnose the depth of such the lesion more carefully.