Supplementary Material for: Lymphatic Metastasis Predicts Better Response to Nivolumab in Recurrent or Metastatic Gastric Cancer: Insights from Tumor-Draining Lymph Node Immunity and Long-Term Outcomes

Background: Nivolumab has become an essential therapeutic agent for patients with advanced or recurrent gastric cancer. However, the impact of metastatic patterns on its clinical efficacy has not been fully elucidated. This study aimed to clarify the association between distinct metastatic patterns and outcomes of nivolumab monotherapy. Methods: Ninety-two patients with advanced or recurrent gastric cancer who received nivolumab were retrospectively analyzed. Clinicopathological variables, including performance status, HER2 expression, and predominant metastatic pattern, were correlated with survival outcomes and response rates. Results: The median observation period was 48.3 months. The median overall and progression-free survival for the entire cohort were 5.80 and 2.43 months, respectively. Patients with ECOG performance status 2–3 had significantly shorter survival than those with PS 0–1. HER2-positive status was associated with longer PFS. When stratified by metastatic pattern, the lymph node metastasis group showed markedly longer survival (median OS 35.1 months, PFS 11.9 months) than the peritoneal (OS 4.66, PFS 2.36 months) and hematogenous/other groups (OS 5.80, PFS 2.10 months). The objective response and disease control rates were also significantly higher in the lymph node group. Conclusion: The pattern of metastatic spread, particularly lymphatic involvement, appears to influence the efficacy of nivolumab in advanced or recurrent gastric cancer. Recognizing metastatic patterns may assist in optimizing patient selection and therapeutic strategies for immune checkpoint blockade.