Impact of Extracapsular Extension of Lymph Node in Adenocarcinoma of the Stomach

Background Extracapsular extension (ECE) of lymph node may have important prognostic impact for patients with adenocarcinoma of the stomach, but it generally is ignored in staging systems and prognostic models. This study aimed to examine the impact that ECE of lymph node has on prognosis for patients with adenocarcinoma of the stomach. Methods The study analyzed 321 consecutive patients with gastric cancer who underwent radical gastrectomy between January 2008 and December 2015. None of these patients had distant metastases. Lymph node metastases were found in 187 patients. The ECE grade was evaluated according to the previously described system used in head and neck cancers. Deposits of cancer cells in sub-serosal fat without a recognizable lymph node were classified as ECE grade 4. Survival outcomes were compared using Kaplan–Meier and Cox regression analyses. A nomogram was constructed using identified significant prognostic factors. The predictive accuracy and model performance were measured by the concordance index (C-index). Results Patients with ECE(+) showed significantly worse 3-year overall survival (OS) and disease-free survival (DFS) than those without ECE. In the sensitivity analysis, ECE had independent prognostic value for both 3-year OS and 3-year DFS, whereas ECE grading showed little impact on mortality trend or disease progression trend. The ECE-based nomogram showed a significantly higher C-index than the pathological tumor and node staging (pTN) staging system. Conclusions The adverse prognostic impact of ECE was validated. Sub-serosal tumor deposits without recognizable lymph node tissue are recommended for inclusion in the ECE definition. A nomogram involving ECE could provide better individual prediction of survival for patients with lymph node-positive gastric cancer.