title: Multivariate analysis of prognostic factors in gastric cancer patients using additive hazards regression models.
abstract: OBJECTIVE
  Gastric cancer is the second leading cause of cancer death worldwide and is the most common type of cancer in Iran. The objective of this research was to apply additive hazards models to the study of survival of patients with gastric cancer and to compare with results obtained using the Cox model.
  
  
  METHODS
  We retrospectively studied 213 patients with gastric cancer who were registered in one referral cancer registry center in Tehran, Iran. Age at diagnosis, sex, presence of metastasis, tumor size, histology type, lymph node metastasis, and pathologic stages were entered into analysis using the Cox model and additive hazard models. To visualize a covariate effect over time, the estimated cumulative regression function by the Aalen's model was examined.
  
  
  RESULTS
  The five-year survival rate and the median life expectancy in the studied patients were 14.6% and 29.6 months, respectively. Multivariate Cox and Additive hazards models analysis identified age at diagnosis, tumor size and pathologic stage as independent prognostic factors for the survival of patients with gastric cancer. Moreover, pathologic stage had a late or delayed effect according to the Aalen's plot. Other clinicopathological characteristics were not statistically significant.
  
  
  CONCLUSIONS
  Since Cox and Aalen models give different aspects of the association between risk factors and the study outcome, it seems desirable to use then together to give a more comprehensive understanding of data. Our results also suggest that early detection of patients at younger age and in primary stages is important to increase survival of patients with gastric cancer.
authors.affiliation: Department of Biostatistics, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran.
authors.forename: Saman
authors.initials: S
authors.lastname: Maroufizadeh
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Hajizadeh
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Baghestani
authors.forename: Seyed Reza
authors.initials: SR
authors.lastname: Fatemi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007492:Iran; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging / Q000379:methods; D011379:Prognosis; D016016:Proportional Hazards Models; D012042:Registries; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000401:mortality* / Q000473:pathology*; D015996:Survival Rate