Clinical Features and Survival of Young Adults with Stage IV Gastric Cancer: A Japanese Population-based Study

Abstract Purpose: With the aging of society, the age of patients with gastric cancer (GC) in Japan has been increasing. However, there are few documented outcomes for young patients with stage IV GC. We investigated the clinical characteristics and prognosis of patients with stage IV GC aged under 40 years using a dataset from an integrated population-based cohort study.Methods: We conducted this multicenter population-based cohort study to determine whether earlier onset of GC was a poor prognostic factor. We enrolled patients with metastatic GC aged under 40 years (young group) and those aged between 60 and 75 years (middle-aged group). Patients were histologically diagnosed as having gastric adenocarcinoma. We evaluated the overall survival (OS) of both groups and the hazard ratio (HR) for OS based on age. The adjusted HR with 95% confidence interval (CI) was evaluated using the Cox proportional hazards model after adjusting for confounding factors, including sex, histology, number of metastatic lesions, surgical resection, and chemotherapy.Results: This study enrolled 555 patients. The patients were classified into the young group (n=20) and the middle-aged group (n=535). The median OS values were 5.7 months and 8.8 months in the young and middle-aged groups, respectively (P=0.029). The adjusted HR (95% CI) of the young group was 1.88 (1.17–3.04, P=0.009).Conclusions: Age was an independent prognostic factor in patients with stage IV GC. Further studies investigating the genomic characteristics of GC and exploring more effective chemotherapeutic agents are required.