Finding the minimum number of retrieved lymph nodes and negative lymph nodes in gastric cancer surgery: a real-world study

Background: Lymph node retrieval deficiency can lead to understagement and postoperative cancer recurrence, it is crucial to establish the standard number of retrieved lymph nodes (rLNs) and negative lymph nodes (nLNs) for patients undergoing gastrectomy. Methods: Patients who has gastric adenocarcinoma and underwent either radical subtotal gastrectomy (RSG) or radical total gastrectomy (RTG) between 2000 and 2022 were retrospectively included. We utilized restricted cubic spline (RCS) analysis to determine the ideal threshold for rLNs and nLNs. Survival analysis was conducted using Kaplan-Meier (KM) curves, log-rank tests and forest plots. Propensity score matching (PSM) was utilized to balance parameters between two groups. The median follow-up time for this study was 3,095 days. Results: Our study found that there are significant tumor characteristic differences between RSG and RTG. For patients with N0-N3a stage undergoing RSG, retrieving≥24 lymph nodes intraoperatively were associated with better prognosis both before and after PSM (OS: P <0.001, P =0.019); whereas for N3b stage, at least 32 rLNs were required (OS: P =0.006, P =0.023). Similarly, for patients with N0-N3a stage undergoing RTG, retrieving≥27 lymph nodes intraoperatively were associated with better prognosis both before and after PSM (OS: P <0.001, P =0.047); whereas for N3b stage, at least 34 rLNs were required (OS: P <0.001, P =0.003). Additionally, for patients undergoing RSG, having ≥21 nLNs (OS: P <0.001, P =0.013), and for those undergoing RTG, having ≥22 nLNs (OS: P <0.001, P <0.001), were also associated with better prognosis both before and after PSM. Conclusions: For patients receiving RSG, rLNs should reach 24 when lymph nodes are limited, and 32 when lymph node metastasis is more extensive, with a minimum number of nLNs ideally reaching 21. Similarly, for patients receiving RTG, rLNs should reach 27 when lymph nodes are limited, 34 when lymph node metastasis is more extensive, and a minimum number of nLNs ideally reaching 22.