Clinical outcomes of SM invasion after ESD: A single center study

Aims Endoscopic treatment of early gastric cancer (EGC) is less invasive than surgery, reduces medical costs, improves quality of life, and is equally effective. However, EGC with undifferentiated histology or submucosal invasion is generally not considered suitable for endoscopic treatment. Traditionally, endoscopic treatment is indicated for differentiated EGCs confined to the mucosa, with elevated tumors<2 cm and depressed types<1 cm without ulceration. This study aims to evaluate the clinical outcomes of endoscopic submucosal dissection (ESD) for EGC with submucosal (SM) invasion.

Methods Among 88 cases of ESD for EGC at our center between July 2021 and December 2023, 10 involved mucosal invasion, 7 showed SM invasion, and 6 were undifferentiated (1 well-differentiated adenocarcinoma). ESD was indicated for mucosal cancer (M cancer) based on endoscopic findings, with or without prominent ulceration. Some patients who rejected surgery or were unfit for surgery received ESD, despite undifferentiated histology or SM invasion (SM1) on endoscopic assessment. Pre-ESD pathology was confirmed by biopsy reports from our or referring hospitals. Submucosal invasion was categorized as SM1 (< 500 μm), SM2 (> 500 μm), or SM3 based on tissue depth. EGC was classified as differentiated if well- or moderately-differentiated, and as undifferentiated if poorly differentiated or signet ring cell cancer. Follow-up endoscopy and biopsy were performed 3 months post-treatment.

Results Post-ESD pathology confirmed SM invasion in 7 cases: 1 case (14.3%) of differentiated cancer and 6 cases (85.7%) of undifferentiated cancer. The complete resection rate was 100%. All lesions (100%) involved SM2/3 invasion. Larger tumor size and deeper SM invasion were significantly associated with undifferentiated cancers (P<0.000) compared to tumors<20mm. The mean follow-up period was 3.4±0.5 months, with no local recurrence observed during this time.

Conclusions Undifferentiated EGC is more likely to invade the submucosa, even in small lesions, often spreading in a subepithelial or discontinuous pattern. This makes endoscopic treatment challenging due to difficulty in clearly defining lesion boundaries before ESD. EGC with submucosal invasion is generally excluded from ESD indication due to a high (10-25%) risk of lymph node metastasis. Despite these factors, some older patients prefer ESD over surgery. In conclusion, undifferentiated or larger EGCs have a high rate of SM invasion post-ESD. However, for cases diagnosed as undifferentiated or SM-invading post-ESD, short-term follow-up remains feasible.

Publication History

Article published online:
27 March 2025