The impact of lymph node count on survival in gastric cancer

The Union for International Cancer Control/American Joint Committee on Cancer (UICC/AJCC) classifies the N stage of gastric cancer based on the metastatic lymph node (LN) count [1,2]. N stage is important for determining treatment strategies and predicting prognosis along with tumor depth (pT stage), and harvesting more than 15 LNs is recommended for proper N staging. Inappropriate LN count results in an inappropriate node-negative result, leading to a lower overall stage, referred to as stage migration. Stage migration shows a worse survival than that of appropriately assessed LN count. However, a large LN count shows better prognosis, suggesting the prognostic significance of the LN count. Most of surgeons agree on the extent of LN dissection, which minimizes stage migration, in order to compare prognosis. Experienced surgeons not only perform LN dissection but also perform LN harvest for pathological examination. In Korea and Japan, D2 LN dissection is the standard LN dissection guideline for gastric cancer, and gastric surgeries are performed by experienced surgeons at hospitals specializing in gastric cancer surgery. There is a tendency to perform LN harvest during surgery, minimizing the possibility of missing positive LNs. Recently, suspicions have been raised that stage migration is exaggerated in meta-analysis studies, arguing that although there is evidence that fat clearance and methylene blue staining during LN harvest increases LN count [2], there is no evidence that this increases LN positivity and upstaging [3]. Some studies also reported that LN count is an indicator for host immunologic role against tumor dissemination [4]. However, there is no direct evidence, and more studies need to be conducted. The purpose of this study was to determine the immunologic role of LN and stage migration by assessing LN count and metastatic LN count. Original Article Korean Journal of Clinical Oncology 2018;14:120-127 https://doi.org/10.14216/kjco.18021 pISSN 1738-8082 ∙ eISSN 2288-4084