One-dimensional and 2-dimensional tumor size measurement for prediction of lymph node metastasis in differentiated early gastric cancer with minute submucosal invasion

Background and Aims Differentiated minute submucosal cancers measuring ≤3 cm that exhibit no lymphovascular invasion are considered eligible for endoscopic resection; however, the ≤3-cm criterion remains debatable. The aim of this study was to verify the optimal tumor size cutoff for endoscopic resection eligibility, and to determine whether 2-dimensional tumor size measurement would be more accurate for this purpose. Methods The clinicopathologic data for 574 patients undergoing curative surgery for differentiated minute submucosal cancer were reviewed retrospectively. A receiver operating curve analysis and bootstrapped samples were used to identify the optimal cutoff values for predicting lymph node (LN) metastasis. Results Four hundred fourteen patients were eligible for the study. LN metastasis accompanied 2.5% of differentiated minute submucosal cancers that were ≤3 cm in size and lacked lymphovascular invasion. There was no lymph node metastasis in the tumors with 1-dimensional sizes ≤1.0 cm and 2-dimensional sizes ≤1.0 cm². When 10,000 bootstrapped data were used, optimal cutoff values were 2.9 cm (LN metastasis: 2.1%) and 8.3 cm² (LN metastasis: 2.5% incidence) for 1- and 2-dimensional tumor size, respectively. Although the area under the curve was 0.611 (P = .046) for 2-dimensional size, specificity and accuracy were greater for the dichotomized 2-dimensional measure than for the dichotomized 1-dimensional measure (P < .001, McNemar test). In addition, 2-dimensional tumor size was the only significant risk factor for LN metastasis (odds ratio, 1.09; 95% confidence interval, 1.01-1.20). Conclusions One- and 2-dimensional cutoff values of 2.9 cm and 8.3 cm² might be suitable for patients at high risk of postoperative morbidity and mortality. Two-dimensional tumor size is an acceptable measurement method for estimating the risk of LN metastasis.