Association Between Metastatic Pattern and Prognosis in Stage IV Gastric Cancer: Potential for Stage Classification Reform.

Abstract

This study aims to clarify the association between metastatic pattern and prognosis in stage IV gastric cancer, with a focus on patients presenting with metastases limited to nonregional lymph nodes. In this retrospective cohort study, the National Cancer Database was used to identify patients ≥ 18 years of age diagnosed with stage IV gastric cancer between 2016 and 2019. Patients were stratified according to pattern of metastatic disease at diagnosis: nonregional lymph nodes only ("stage IV-nodal"), single systemic organ ("stage IV-single organ"), or multiple organs ("stage IV-multi-organ"). Survival was assessed by Kaplan-Meier curves and multivariable Cox models in unadjusted and propensity score-matched samples. Overall, 15,050 patients were identified, including 1,349 (8.7%) stage IV-nodal patients. Most patients in each group received chemotherapy [68.6% of stage IV-nodal patients, 65.2% of stage IV-single organ patients, and 63.5% of stage IV-multi-organ patients (p = 0.003)]. Stage IV-nodal patients exhibited better median survival (10.5 months, 95% CI 9.7-11.9, p < 0.001) than single organ (8.0, 95% CI 7.6-8.2) and multi-organ (5.7, 95% CI 5.4-6.0) patients. In the multivariable Cox model, stage IV-nodal patients also exhibited better survival (HR 0.79, 95% CI 0.73-0.85, p < 0.001) than single organ (reference) and multi-organ (HR 1.27, 95% CI 1.22-1.33, p < 0.001) patients. Nearly 9% of clinical stage IV gastric cancer patients have their distant disease confined to nonregional lymph nodes. These patients were managed similarly to other stage IV patients but experienced a better prognosis, suggesting opportunities to introduce M1 staging subclassifications.