Endoscopic Resection of Undifferentiated Early Gastric Cancer

Area of Science:

• Gastroenterology
• Surgical Oncology
• Oncology

Background:

• Endoscopic resection (ER) is standard for early gastric cancer (EGC) with low lymph node metastasis (LNM) risk.
• Undifferentiated EGC (UD-EGC) traditionally has limited ER indications due to higher LNM and infiltrative growth risks compared to differentiated EGC (D-EGC).
• Previous guidelines cautiously recommended ER for specific UD-EGC cases (intramucosal, ≤2 cm, no ulceration).

Purpose of the Study:

• To evaluate the long-term outcomes of endoscopic submucosal dissection (ESD) for UD-EGC.
• To assess the expanded indications for ER in UD-EGC based on recent evidence.

Main Methods:

• A prospective multicenter study (JCOG 1009/1010) involving 275 patients with UD-EGC (cT1a, ≤2 cm, without ulceration) treated with ESD.
• Analysis of 5-year overall survival (OS) rates and comparison with established thresholds.

Main Results:

• The 5-year OS was 99.3% (95% CI, 97.1%-99.8%), significantly exceeding the threshold of 89.9%.
• These outcomes support the updated Japanese guidelines classifying this indication as 'absolute'.
• Current evidence grades and recommendations for ER of UD-EGC vary across Japan, Korea, and Western countries.

Conclusions:

• Endoscopic resection, specifically ESD, is a safe and highly effective treatment for selected UD-EGC patients.
• The success of ESD in this study supports its expansion as an 'absolute indication' in Japan.
• International consensus and further discussion are necessary to generalize ER indications for UD-EGC globally.