Validity of endoscopic resection for clinically diagnosed T1a-MM/T1b-SM1 N0 M0 esophageal squamous cell carcinoma

Background Previous guidelines have not described clear recommendations for performing endoscopic resection (ER) of T1a-muscularis mucosa (MM)/T1b-submucosal (SM1) cancers that have invaded ≤ 200 μm because these are considered to have a non-negligible risk of metastasis based on previous analyses of pathologically diagnosed (p)MM/SM1 cancers. Considering that the indication for ER is determined based on a clinical diagnosis, the applicability of ER should be investigated in clinical (c)MM/SM1 but not pMM/SM1 cancers. This study aimed to evaluate validity of ER for cMM/SM1 cancers. Methods In total, 175 cMM/SM1 esophageal squamous cell carcinoma cases that were endoscopically or surgically resected between January 2008 and December 2018 were identified from a prospectively maintained database. We histologically evaluated resected specimens and divided them into low- ( n = 92) and high-risk ( n = 83) cancers for metastasis. Results Univariate analysis showed that longer tumor length and larger circumferential extent were significantly correlated with high-risk cancer ( P 3/4 and