S1336 Absolute vs Expanded Criteria Lymph Node Metastasis in Early Gastric Cancer: A Novel U.S. Criterion

Abstract

INTRODUCTION: Endoscopic resection (ER) for early gastric cancer (EGC) is the principal treatment for lesions fulfilling the absolute and expanded criteria (Exp) developed by the Japanese Gastric Cancer Association. Cohorts showing a minimal risk of lymph node metastasis (LNM) are primarily from eastern Asia. Endoscopic management is adopted in the West, despite the lack of data in Western cohorts. We aims to describe the incidence of LNM by absolute and Exp criteria in the U.S. population using the Surveillance, Epidemiology, End Results (SEER) database, and to define a novel absolute criteria (absence of LNM) for the U.S. METHODS: EGC data was analyzed in the U.S. SEER database. To identify novel absolute criteria in the U.S., we assumed that all the lesions were positive for LVI and ulceration, since SEER does not include this data (a limitation of the database). RESULTS: 161,854 gastric cancers were identified. 2020 EGC met inclusion criteria, 781 T1a and 1239 T1b. No LNM cases were noted in T1a well differentiated lesions < 1cm (0/80). In T1a well differentiated lesions < 2cm, the rate of LNM was 1/125 (0.8%). 277 patients fulfilled absolute criteria (T1a, differentiated < 2cm in size), and 8/277 had LNM (2.9%). The Exp criteria 1-4 findings are summarized in Table 1, with LNM ranging from 7.8% to 16.7%. There were 154 lesions fulfilling Exp criteria 1 (T1a, differentiated, >2cm); LNM occurred in 12/154 (7.8%). There were 353 lesions fulfilling the Exp 2 criteria (T1a, differentiated, < 3cm); LNM occurred in 13/353 (3.7%). There were 197 lesions fulfilling the Exp 3 criteria (T1a, undifferentiated, < 2cm); LNM occurred in 13/197 (6.6%). There were 441 lesions fulfilling the Exp criteria 4 (T1b, differentiated < 3cm); LNM occurred in 74/441 (16.7%). No significant differences were noted between the rates of LNM in the absolute vs Exp criteria 2 or 3 respectively (P = 0.5 , P = 0.053), However, Exp criteria 1 and 4 were associated with a higher incidence of LNM respectively (P = 0.02 , P = 0.001). On multivariate logistic regression, tumor size, T stage, grade, and the number of lymph nodes examined were significant predictors of LNM. CONCLUSION: We propose a new absolute criterion in the U.S. for well differentiated T1a EGC < 1cm regardless of the ulcer status and LVI, with 0% LNM; endoscopic resection should be the standard of care for these lesions. The rate of LNM was 0.8% for T1a well differentiated lesions < 2cm regardless of ulcer status and LVI. The Exp criteria 1 and 4 had an increased risk of LMN.Table 1.: EGC study characteristicsTable 2.: Lymph node metastasis