[Comparison of long-term outcomes between endoscopic submucosal dissection and surgical resection for early gastric cancer with undifferentiated histology]

Objective: Endoscopic submucosal dissection (ESD) of undifferentiated early gastric cancer (UD-EGC) remains controversial due to high positive rate of horizontal and vertical resection margins and the risk of lymph node metastasis. The purpose of this study was to compare long-term outcomes of patients with UD-EGC undergoing ESD versus surgery. Methods: This study was a retrospective cohort study. Inclusion criteria: (1) patients with early gastric cancer undergoing ESD or surgical resection; (2) histological types included poorly differentiated adenocarcinoma, poorly differentiated adenocarcima with signet ring cell carcinoma, and signet ring cell carcinoma; (3) no lymph node metastasis or distant metastasis was confirmed by preoperative CT and endoscopic ultrasonography. Exclusion criteria: (1) previous surgical treatment for gastric cancer; (2) synchronous tumors; (3) death with unknown cause; (4) additional surgical treatment was performed within 1 month after ESD. According to the above criteria, clinical data of patients with UD-EGC who received ESD or surgery treatment in Cancer Hospital of Chinese Academy of Medical Sciences from January 2009 to December 2016 were collected. After further comparing the clinical outcomes between the two groups by 1:1 propensity score matching, 61 patients in the ESD group and 61 patients in the surgery group were finally included in this study. The disease-free and overall survivals were analyzed by Kaplan-Meier method. Results: All patients in the two groups completed operations successfully. In the ESD group, the median operation time was 46.3 (26.5, 102.3) minutes, 61 cases (100%) were en-bloc resection, and 57 cases (93.4%) were complete resection. Positive margin was found in 4 (6.6%) patients, of whom 2 were positive in horizontal margin and 2 were positive both in horizontal and vertical margins. In the surgery group, only 1 case had positive horizontal margin and no positive vertical margin was observed. There was no significant difference in the positive rate of margin between the two groups (P>0.05). Median follow-up time was 59.8 (3.0, 131.5) months. The follow-up rate of ESD group and surgery group was 82.0% (50/61) and 95.1% (58/61), respectively. The 5-year disease-free survival rate in ESD group and surgery group was 98.2% and 96.7%, respectively (P=0.641), and the 5-year overall survival rate was 98.2% and 96.6%, respectively (P=0.680). In the ESD group, 1 patient (1.6%) had lymph node recurrence, without local recurrence or distant metastasis. In the surgery group, 1 case (1.6%) had anastomotic recurrence and 1 (1.6%) had distant metastasis. Conclusion: ESD has a sinilar long-term efficacy to surgery in the treatment of UD-EGC.