BACKGROUND This study aimed to investigate risk factors for lymph node (LN) or distant metastasis after non-curative endoscopic resection (ER) of undifferentiated-type early gastric cancer (EGC).

METHODS Of 1124 patients who underwent ER for undifferentiated-type gastric cancer at 18 tertiary hospitals across six geographic areas in Korea between 2005 and 2014, 634 with non-curative ER beyond the expanded criteria were retrospectively enrolled. According to the treatment after ER, patients were divided into additional surgery (n = 270) and follow-up (n = 364) groups. The median follow-up duration was 59 months for recurrence and 84 months for mortality.

RESULTS LN metastasis was found in 6.7% (18/270) of patients at surgery. Ulcer [odds ratio (OR) 3.83; 95% confidence interval (CI) 1.21-12.13; p = 0.022] and submucosal invasion (OR 10.35; 95% CI 1.35-79.48; p = 0.025) were independent risk factors. In the follow-up group, seven patients (1.9%) developed LN or distant recurrence. Ulcer [hazard ratio (HR) 7.60; 95% CI 1.39-35.74; p = 0.018], LVI (HR 6.80; 95% CI 1.07-42.99; p = 0.042), and positive vertical margin (HR 6.71; 95% CI 1.28-35.19; p = 0.024) were independent risk factors. In the overall cohort, LN metastasis rates were 9.6% in patients with two or more risk factors and 1.2% in those with no or one risk factor.

CONCLUSIONS LVI, ulcer, submucosal invasion, and positive vertical margin are independently associated with LN or distant metastasis after non-curative ER of undifferentiated-type EGC. Surgical resection is strongly recommended for patients with two or more risk factors.