Objective:To investigate the impact of the number of examined lymph nodes (ELN) on survival outcomes in gastric cancer patients with postoperative pathological stage pN3b.Methods:This retrospective cohort study included 279 pN3b gastric cancer patients who underwent D2 gastrectomy at Nanfang Hospital, Southern Medical University (September 2008 to April 2023), with 35 patients receiving combination chemotherapy and anti-PD-1 therapy (immunotherapy group) and 244 receiving adjuvant chemotherapy alone (nonimmunotherapy group). Additionally, 422 patients with pN3b from the SEER database (2005 to 2020) were collected as an external validation cohort to determine the optimal cutoff value for the number of lymph nodes examined in the nonimmunotherapy group. The primary endpoints were overall survival (OS) and recurrence-free survival (RFS) in the nonimmunotherapy group of the Nanfang Hospital cohort, stratified by whether the number of examined lymph nodes was above or below the ELN optimal cutoff value. These findings were subsequently validated in the SEER cohort.Results:The optimal ELN cutoff value (34 nodes) was determined using X-tile software and by constructing an ELN-HR fitting model with inflection point identification. In the nonimmunotherapy group, patients with ELN >34 exhibited significantly prolonged survival compared to ELN ≤34 (median OS: 25.0 (95%CI:20.5-29.5) to 17.0 (95%CI:12.7-21.3) months, P=0.004; median RFS: 19.0 (95%CI:15.6-22.4) to 13.0 (95%CI:9.5-16.5) months, P=0.048). Multivariate Cox analysis also showed ELN >34 to be an independent protective factor for both OS (HR=0.576, 95%CI: 0.397-0.836) and RFS (HR=0.701, 95%CI: 0.492-0.998). In the SEER cohort, ELN >34 was associated with a 5-month OS extension (19 to 14 months, P=0.065), with multivariate analysis supporting its independent prognostic significance (HR=0.729, 95%CI: 0.580-0.915, P=0.006). Notably, in the immunotherapy group, patients with ELN >34 ( n=30) achieved a median OS of 41 months, but the median OS had not been reached in the ELN ≤34 group ( n=5) (1 death at 48 months). Conclusion:Higher ELN (>34) correlates with improved survival in nonimmunotherapy-treated pN3b gastric cancer patients. However, in pN3b gastric cancer patients treated with immunotherapy, the optimal ELN threshold requires further exploration to determine.

Objective:To investigate the impact of the number of examined lymph nodes (ELN) on survival outcomes in gastric cancer patients with postoperative pathological stage pN3b.Methods:This retrospective cohort study included 279 pN3b gastric cancer patients who underwent D2 gastrectomy at Nanfang Hospital, Southern Medical University (September 2008 to April 2023), with 35 patients receiving combination chemotherapy and anti-PD-1 therapy (immunotherapy group) and 244 receiving adjuvant chemotherapy alone (nonimmunotherapy group). Additionally, 422 patients with pN3b from the SEER database (2005 to 2020) were collected as an external validation cohort to determine the optimal cutoff value for the number of lymph nodes examined in the nonimmunotherapy group. The primary endpoints were overall survival (OS) and recurrence-free survival (RFS) in the nonimmunotherapy group of the Nanfang Hospital cohort, stratified by whether the number of examined lymph nodes was above or below the ELN optimal cutoff value. These findings were subsequently validated in the SEER cohort.Results:The optimal ELN cutoff value (34 nodes) was determined using X-tile software and by constructing an ELN-HR fitting model with inflection point identification. In the nonimmunotherapy group, patients with ELN >34 exhibited significantly prolonged survival compared to ELN ≤34 (median OS: 25.0 (95%CI:20.5-29.5) to 17.0 (95%CI:12.7-21.3) months, P=0.004; median RFS: 19.0 (95%CI:15.6-22.4) to 13.0 (95%CI:9.5-16.5) months, P=0.048). Multivariate Cox analysis also showed ELN >34 to be an independent protective factor for both OS (HR=0.576, 95%CI: 0.397-0.836) and RFS (HR=0.701, 95%CI: 0.492-0.998). In the SEER cohort, ELN >34 was associated with a 5-month OS extension (19 to 14 months, P=0.065), with multivariate analysis supporting its independent prognostic significance (HR=0.729, 95%CI: 0.580-0.915, P=0.006). Notably, in the immunotherapy group, patients with ELN >34 ( n=30) achieved a median OS of 41 months, but the median OS had not been reached in the ELN ≤34 group ( n=5) (1 death at 48 months). Conclusion:Higher ELN (>34) correlates with improved survival in nonimmunotherapy-treated pN3b gastric cancer patients. However, in pN3b gastric cancer patients treated with immunotherapy, the optimal ELN threshold requires further exploration to determine.