Effect of prior malignancy on the prognosis of gastric cancer and somatic mutation

BACKGROUND: Cancer survivors have a higher risk of developing secondary cancer, with previous studies showing heterogeneous effects of prior cancer on cancer survivors. AIM: To describe the features and clinical significance of a prior malignancy in patients with gastric cancer (GC). METHODS: We identified eligible patients from the Surveillance, Epidemiology, and End Results (SEER) database, and compared the clinical features of GC patients with/without prior cancer. Kaplan-Meier curves and Cox analyses were used to assess the prognostic impact of prior cancer on overall survival (OS) and cancer-specific survival (CSS) outcomes. We also validated our results in The Cancer Genome Atlas (TCGA) cohort and compared mutation patterns. RESULTS: In the SEER dataset, of the 35492 patients newly diagnosed with GC between 2004 and 2011, 4,001 (11.3%) had at least one prior cancer, including 576 (1.62%) patients with multiple cancers. Patients with a prior cancer history tended to be elderly, with a more localized stage and less positive lymph nodes. The prostate (32%) was the most common initial cancer site. The median interval from initial cancer diagnosis to secondary GC was 68 mo. By using multivariable Cox analyses, we found that a prior cancer history was not significantly associated with OS (hazard ratio [HR]: 1.01, 95% confidence interval [CI]: 0.97–1.05). However, a prior cancer history was significantly associated with better GC-specific survival (HR: 0.82, 95% CI: 0.78–0.85). In TCGA cohort, no significant difference in OS was observed for GC patients with or without prior cancer. Also, no significant differences in somatic mutations were observed between groups. CONCLUSION: The prognosis of GC patients with previous diagnosis of cancer was not inferior to that of primary GC patients.