[Minimum negative lymph node dissection during radical gastrectomy for gastric cancer: a 22-year, single-center...

Objective: To establish the minimum number of negative lymph nodes (nLN) required for patients undergoing gastrectomy. Methods: This was a retrospective cohort study with inclusion criteria as follows: (1) radical gastrectomy; (2) histologically confirmed adenocarcinoma; (3) complete tumor staging information; and (4) known number of lymph nodes harvested. The exclusion criteria were: (1) other concurrent malignant tumors; (2) metastatic or recurrent gastric cancer; (3) initial surgery performed at another hospital; (4) preoperative neoadjuvant therapy; (5) distant metastasis; and (6) incomplete clinical data or follow-up information. Based on the above criteria, a total of 11 167 patients with gastric adenocarcinoma who underwent radical subtotal gastrectomy (RSG) or radical total gastrectomy (RTG) in the Department of Gastric Surgery, Fudan University Shanghai Cancer Center between January 1, 2000, and December 31, 2022, were included in the study. Among them, there were 7 596 cases in the RSG group and 3 571 cases in the RTG group. Restricted cubic spline (RCS) analysis was used to determine the ideal threshold for nLN for RSG and RTG patients. Survival analysis was conducted using Kaplan-Meier (KM) curves and log-rank tests, and propensity score matching (PSM) was utilized to balance parameters between two groups. Furthermore, subgroup analysis was conducted for RSG patients based on tumor location (upper, middle and lower) to determine the minimum number of nLN in each subgroup. Results: For patients who underwent RSG, the mean number of nLN was 21.9, with a median of 21. RCS analysis showed that more than 21 nLN was associated with better survival. Moreover, both pre- and post-PSM analysis confirmed that patients with nLN ≥21 had better survival benefits compared to those with nLN <21 (overall survival [OS]: P<0.001 before PSM, P=0.013 after PSM; disease-free survival [DFS]: P<0.001 before PSM, P=0.013 after PSM). For patients who underwent RTG, the mean number of nLN was 23.5, with a median of 22. Here RCS analysis indicated that more than 22 nLN was associated with better postoperative survival in RTG patients, and both pre- and post-PSM analysis confirmed that patients with nLN ≥22 had better survival benefits compared to those with nLN<22 (OS: P<0.001 both before and after PSM; DFS: P<0.001 both before and after PSM). Subgroup analysis showed that for RSG patients with tumor located in the upper part, having ≥17 nLN (OS: both P<0.001), and for RSG patients with tumor located in the middle and lower part, having ≥22 nLN (OS: both P<0.001), were associated with better prognoses. Conclusions: For patients who receive RSG, the minimal number of nLN is ideally ≥21 (upper ≥17, middle and lower ≥22). Similarly, for patients who receive RTG, the minimum number of nLN ideally is 22.