All-Cause and Cause-Specific Mortality by SEER Stage in Gastric Cancer: A Nationwide Population-Based Cohort Study

Background: Despite significant advances in diagnosis and treatment, gastric cancer remains a major global malignancy. This study aimed to evaluate the impact of Surveillance, Epidemiology, and End Result (SEER) stages on all-cause and cause-specific mortality in gastric cancer. Methods: This nationwide population-based cohort study analyzed data from the Cancer Public Library Database (CPLD). Patients aged ≥ 30 years diagnosed with gastric cancer between 2012 and 2019 were followed up until 31 December 2020. Cox proportional hazards models and Fine-Gray models were used to compare the risk of all-cause and cause-specific mortality based on SEER stages. The Kaplan-Meier method and cumulative incidence functions were applied to analyze cumulative incidences of all-cause and cause-specific mortality. Statistical significance was assessed using the log-rank test and Gray's test. Additionally, a subgroup analysis was performed. Results: Among 218,491 individuals, 59,952 died during a median follow-up of 3.62 years. Compared with the localized stage, the risk of all-cause mortality was 4.31 and 24.73 times higher in patients with the regional and distant stages, respectively, after adjusting for sex, age, income, residential area, and comorbidities. The regional stage was associated with an 8.70-, 6.08-, 1.28-, and 1.43-fold higher risk of stomach cancer death, cancer death, cardiovascular death, and respiratory death, respectively. The distant stage was associated with 51.67-, 35.97-, 1.74, and 1.54-fold higher risk of stomach cancer death, cancer death, cardiovascular death, and respiratory death, respectively. Conclusions: Higher SEER stage in gastric cancer is associated with an increased risk of all-cause mortality, gastric cancer-specific mortality, overall cancer mortality, cardiovascular disease-related mortality, and respiratory disease-related mortality. Notably, cardiopulmonary mortality increased with advancing SEER stage, particularly among younger patients, underscoring the need for vigilant monitoring.