Document Type: Methodological papers
Modeling in Health Research Center, School of Public Health, Department of Epidemiology and Biostatistics, Shahrekord University of Medical Sciences, Shahrekord, Iran.
Department of Epidemiology and Reproductive Health, Reproductive Epidemiology Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran.
Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
School of Public Health, University of Alberta, Edmonton, Alberta, Canada.
Background: Esophageal cancer (EC) and Gastric cancer (GC) have been identified as two of the most common
cancers in the northeastern regions of Iran. The increasing rates of these types of cancers requires attention. This study
aims to assess the potential risk factors for these two cancers and then determine shared risk factors between them
in a population of Iranian patients using parametric survival models. Methods: This retrospective cohort study was
conducted using 127 patients with EC and 184 patients with GC in East Azarbaijan, Iran who were diagnosed and
registered during the years 2009-2010 in Iran’s National Cancer Control Registration Program and were followed for
five years. Parametric survival models were used to find the risk factors of the patients. Akaike Information Criteria was
used to identify the best parametric model in this study. Interaction analysis was used to determine shared risk factors
between EC and GC. Results: The mean (±standard deviation) age of diagnoses for EC and GC were 66.92(±11.95) and
66.5(±11.5) respectively. The survival time ranges of GC patients was (0.07-70.33) and the survival time ranges were
from 0.10 to 69.03 months for EC patients. Multivariable Log- logistic model showed that being married (OR=2.25, 95%
CI: 1.33 - 3.81) for EC patients and Esophagectomy surgery for EC (OR: 1.62, 95% CI: 1.04 – 2.55) and GC (OR: 1.60,
95% CI: 1.02 – 2.53) had significant effects on survival. Age at the time of diagnosis, job status, and Esophagectomy
surgery were statistically comparable regarding their magnitude of effect on survival of two cancers (all Ps>0.05).
Conclusion: Esophagectomy surgery and being married were important risk factors in EC and GC. The log-logistic
model was the most appropriate statistical approach to identify significant risk factors on survival of both cancers.