Clinical Outcomes of Follow-Up Observation After Endoscopic Submucosal Dissection for Esophageal Squamous Cell Carcinoma Invading the Muscularis Mucosa Without Lymphovascular Involvement.

BACKGROUND: The therapeutic approach after endoscopic submucosal dissection (ESD) for esophageal squamous cell carcinoma (ESCC) diagnosed as pathological T1a-muscularis mucosa (pT1a-MM) without lymphovascular involvement (LVI) remains uncertain. We aimed to determine whether observation after ESD is acceptable for patients without LVI showing pT1a-MM cancer. METHODS: We retrospectively registered 566 ESCC patients who were treated with ESD at ten institutions between January 2007 and December 2015. Of those, 447 cases showing pT1a-epithelium/lamina propria mucosa (EP/LPM) without LVI and vertical margin (VM) (EP/LPM group), and 41 cases showing pT1a-MM without LVI and VM (MM group) were analyzed in this investigation. The clinical outcomes were assessed between the groups. RESULTS: The 5 year cumulative incidence of metastatic recurrence was 0.5% and 3.3% in the EP/LPM and MM groups, respectively (P = 0.121). Two cases showing pT1a-EP/LPM and one showing pT1a-MM experienced lymph node recurrence. The 5 year cumulative incidence of local recurrence was 1.5% and 3.8% in the EP/LPM and MM groups, respectively (P = 0.455). The 5 year disease-specific survival (DSS) rate was 99.3% and 96.6% in the EP/LPM and MM groups, respectively (P = 0.118), whereas the 5 year overall survival rate was significantly higher in the EP/LPM group than in the MM group (92.6% versus 81.1%, respectively; P = 0.021). CONCLUSIONS: As regards metastatic recurrence and DSS, ESCC patients with pT1a-MM without LVI showed favorable outcomes that were equivalent to those with pT1a-EP/LPM, even when they were not treated with additional therapy after ESD.