Prognostic factor for patients with gastric cancer using the Aalen's additive hazards model

Gastric cancer is the second leading cause of cancer death worldwide and is the most common type of cancer in Iran. The objectives of this study were to assess the effects of prognostic factors on survival of patients with gastric cancer using the Aalen additive hazards model, and to illustrate the advantage of Aalen’s plot. Information of total of 213 patients with gastric cancer who underwent surgery in the gastroenterology ward of Taleghani hospital in Tehran between 2003 and 2008 were included in this historical cohort study. Age at diagnosis, sex, presence of metastasis, tumor size, histology type, lymph node metastasis, and pathologic stages were entered into analysis using the Aalen additive hazard model. To visualize a covariate effect over time, the estimated cumulative regression function by the Aalen’s model is examined. The univariate and multivariate analysis identified that age at diagnosis, tumor size and pathologic stage were independent prognostic factors for the survival of patients with gastric cancer (p<0.05). Moreover, pathologic stage has a late or delayed effect according to the Aalen’s plot. Other clinicopathological characteristics were not statistically significant (p>0.05). In spite of using Cox model in survival analysis by many researchers, Aalen’s model may yield new insights in prognostic studies of survival time of patients with gastric cancer over time. Our results suggest that early detection of patients in younger age and in primary stages is important to increase survival from gastric cancer.