Effects of Life Table Models on the Evaluation of Excess Mortality

BACKGROUND Northern regions of Iran have been encountered to dominate malignancies of gastrointestinal (GI) tract. We aimed to examine the excess mortality due to the GI tract cancer in Mazandaran province. METHODS Socio-demographic and clinical data of 484 patients with GI cancer collected during the years 1990-1991 were available from Babol Cancer Registry Center in Iran. Patients were followed-up for a maximum period of 15 years by the year 2006. The Coale-Demeny life tables were established for each combination of birth cohort and sex of patients, and were considered as the reference population in estimating excess mortality rates. The relative and additive mortality models for excess mortality estimation were used. RESULTS The sample of subjects encompassed 66.3% men and 33.7% women, with mean age 58.26 ± 10.90 years. Esophageal cancer appeared to be the most common one, and endoscopy was the general method for cancer detection. Survival rate in 15 years following diagnosis was nearly 6%. Excess mortality estimated by each of the relative and additive models reached the most value in the first two years of observation in both genders and according to each of the Coale-Demeny regional patterns. CONCLUSION considering individuals in a population come from different cohorts with different mortality patterns, it might be recommended to construct distinct life tables for different birth cohorts when estimating excess hazard. The West model as a general pattern is recommended to represent mortality patterns in countries whose registration systems either do not exist or are so affected by omission and other errors.