Estimating the Net Survival of Patients with Gastric Cancer in Iran in a Relative Survival Framework

Background: Iran is an Eastern Mediterranean region country with the highest rate of gastric cancer. The present study aimed to evaluate the 5-year net survival of patients with gastric cancer in Iran using a relative survival framework. Methods: In a cross-sectional study, using life-table estimation of relative survival, we reported 1- to 5-year relative survival regarding age, sex, disease stage, pathology, and adjuvant therapies via modeling excess mortality. All the analyses were done applying Stata 11.2 with a confidence level of 95%. Results: Data on 330 patients (aged 32-96 y), who were comprised of 228 (69.1%) men and 102 (30.1%) women with gastric cancer and were followed up for 10 years, were analyzed. Adenocarcinoma was the most common malignancy (281 [85.2%] patients), and 248 (75.1%) patients were at stage 3 or stage 4. The 1-and 5-year net survival rates after surgery were 67.96 (95% CI: 62.35-72.98) and 23.35 (95% CI: 17.94-29.28), respectively. Higher stages (P=0.001), older ages (P=0.007), and less use of adjuvant therapies (P< 0.001) were independently associated with excess mortality. Conclusion: It is recommended to use the relative survival framework to analyze the survival of cancer patients as an alternative approach not only to eliminate biases due to competing risks and their dependencies but also to estimate the cure at the population level concerning the most important individual characteristics. Our findings showed that the survival rate of gastric cancer in Iran is lower than that in most developed countries in terms of net survival.