Survival Analysis of Gastric Cancer Patients Using Illness-Death Model In Kerman City, Southeast Iran during 2001-2016

BACKGROUND Gastric cancer (GC) is the fifth most common cancer and the third most common cause of cancer death worldwide. The aim of this study was to investigate the factors affecting the survival of patients with GC using the illness-death model (metastasis as an intermediate event). METHODS In this retrospective cohort study, 339 patients with GC who were referred to Shahid Bahonar and Afzalipour Hospitals in Kerman, Southeast Iran during 2001-2016 were included. Demographic, therapeutic, and clinical data were collected from the patients’ medical records. To evaluate the factors affecting patients’ survival and the relationship between the factors, the illness-death model (metastasis as an intermediate event) was used. RESULTS One, three, and five-year survival rates in patients with GC were estimated to be 63%, 40%, and 30%, respectively. The results of analysis of illness-death model showed that age (HR = 0.98, 95% CI: 0.97- 0.99; p = 0.007) and histological grade (HR = 1.77; 95% CI: 1.68- 2.67; p =0.007) affected metastasis whereas history of cigarette smoking (HR = 1.89; 95% CI: 1.08- 3.3; p = 0.02) and chemotherapy (HR = 0.63; 95% CI: 0.4-0.93; p = 0.02) affected death hazard without metastasis. History of opium use (HR=2.11; 95% CI: 1.17- 3.8; p = 0.002), family history of GC (HR = 2.48; 95% CI: 1.2-5.15; p = 0.01) and histological grade (HR = 1.85; 95% CI: 1.11- 3.08; p = 0.02) were identified as factors affecting death hazard in patients with metastasis. CONCLUSION According to the results, patients’ age at the time of diagnosis and histological grade have a significant effect on the occurrence of metastasis. In addition, using the disease- death model, a complete understanding of the behavior and effects of the studied variables on different disease states can be realized.