Incidence and Risk Factors of Remnant Gastric Cancer after Gastrectomy for Gastric Cancer: A Population-Based Study from the SEER Database (2000-2020)

Background. Gastric cancer (GC) constitutes a major health problem in the U.S., of which remnant gastric cancer (RGC) occurs less frequently. The rate of RGCs after gastrectomy for GC is increasing recently due to improved survival and screening, however, their incidence and risk have not been reported in the U.S. population. The objective of this study was to evaluate the incidence and elevated risk of RGC after GC gastrectomy in the U.S., and to identify the risk factors. Methods. Patients diagnosed with first primary GC in 2000–2015 and those who developed RGC were identified from Surveillance, Epidemiology and End Results (SEER) database. Fine-Gray regression was used to estimate the cumulative incidence and to identify risk factors. Standardized incidence ratios (SIRs) were calculated by Poisson regression to compare the risk with the general population. Results. Among 21566 patients included in the cohort, 227 developed RGC. The 20-year cumulative incidence of RGC was 1.88%. Multivariate analysis showed that hazard ratios were significantly higher in patients with age over 55 years, widowed and single marital status, unspecified tumor site, and T4 tumor, but lower in patients with diagnosis in 2010–2015, female sex, and $75000 + income. SIR was 7.70 overall and > 4.5 in each stratum. Conclusions. Cumulative incidence and risk for RGCs increased continuously in patients underwent GC gastrectomy. Earlier diagnosis, older age, male sex, marital status, lower income, and invasion depth are independent risk factors for RGC development. Close and lifelong endoscopy surveillance should be recommended for these patients.