Lymph node metastasis in early gastric cancer: evaluation of a novel method for measuring submucosal invasion and development of a nodal predicting index.

After endoscopic resection of early gastric cancer (EGC), it is imperative to accurately determine whether follow-up surgery is indicated, since this technique is used as a first line of treatment. Herein, we developed a scoring system to indicate the risk of lymph node metastasis in submucosal EGC (smEGC), and present a novel method to measure depth of submucosal invasion. In our series, 15.9% of the smEGC presented with lymph node metastasis. A nodal prediction index, based on the variables extracted from the univariate analysis and defined as nodal prediction index = (2.128 × lymphovascular tumor emboli) + (1.083 × submucosal invasion width ≥ 0.75 cm) + (0.507 × submucosal invasion depth ≥ 1000 μm) + (0.515 × infiltrative growth pattern), yielded an area under the receiver operating characteristic curve of 0.809 (P =.000, 95% CI = 0.713-0.096) in a training group, and showed comparable result in validation group (0.886, P =.000, 95% CI = 0.796-0.977). Depth of invasion was statistically higher in the metastatic group when measured from the lowest point of an imaginary line in continuity with the adjacent muscularis mucosa to the point of deepest tumor penetration, but not when using the classic measurement method. The area under the receiver operating characteristic curve of the alternative measurement method was 0.652 (P =.013, 95% CI = 0.550-0.754) compared to 0.620 for the classic measurement method (P =.0480, 95% CI = 0.509-0.731). In deciding whether surgery is indicated after endoscopic submucosal dissection for smEGCs, we recommend to test our alternative method of measuring submucosal invasion and to evaluate our nodal prediction index as an adjunct tool.