Impact of a previous cancer history on the overall survival of patients with primary gastric cancer: A SEER population-based study

Background: The impact of previous cancers on the survival of gastric cancer (GC) patients is still uncertain. To evaluate the impact of a prior cancer history on the overall survival of patients with primary GC. Methods: The Surveillance, Epidemiology, and End Results (SEER) database provided data on patients diagnosed with GC as the first or second primary malignancy between 2010 and 2015 in this retrospective cohort study. Cox proportional hazards models, Kaplan-Meier curves and forest plots were utilized to analyze overall survival. Subgroup analysis was performed based on age, gender, race and prior cancer type. Results: Totally 39,379 were eligible for this study, including 7403 (18.8%) with a previous cancer history. A previous cancer was an independent risk factor for overall survival [hazard ratio (HR) = 1.103, 95% confidence interval (CI): 1.070-1.138]. For GC patients aged 40-60 years (HR = 1.191, 95% CI: 1.084 -1.308) and >= 60 years (HR = 1.093, 95% CI: 1.058-1.13) at diagnosis, a previous cancer was significantly associated with worse overall survival. GC patients with previous oral cavity and pharynx cancer (HR = 1.249, 95% CI: 1.038-1.501), respiratory system cancer (HR = 1.177, 95% CI: 1.076-1.286), female genital system cancer (HR = 1.169, 95% CI: 1.011-1.351), or lymphoma cancer (HR = 1.192, 95% CI: 1.023 -1.389) had shorter overall survival than GC patients without a previous cancer. Conclusion: A previous cancer adversely affected the overall survival of GC patients. Specifically, GC patients aged > 40 years, or with oral cavity and pharynx cancer, respiratory system cancer, female genital system cancer, or lymphoma cancer had inferior overall survival. These patients should obtain more attention and get individualized treatment to improve prognosis, and clinical trial eligibility criteria could be reconsidered for particular age and cancer types.