Temporal Pattern and Age-Period-Cohort Analysis of Breast Cancer Incidence in Iranian Women (2009-2017)

Background: Breast cancer accounted for 28.1% of all female cancers in 2020 in Iran. This study was conducted to evaluate the time trend of breast cancer incidence and to identify the changes of breast cancer incidence in age, period, and birth cohorts in Iran, in the 2009-2017 timeframe. Methods: Annual cancer statistics for female breast cancer were obtained from the Iranian National Population-based Cancer Registry (INPCR) database from 2009 to 2017. The age-period-cohort (APC) analysis was used to evaluate the time trend of breast cancer incidence in age, period and birth cohorts between 2009 and 2017. R package (Epi) was used to analyze data. Results were considered statistically significant at P < 0.05. Results: The age effect showed an increased incidence of breast cancer until the age of 45, and after this age the speed of increase was slower until 65 years. There was an increased diagnosis in 2015-2017 (period effect) for many age groups, especially in the 70- and over 80-year-old group. Conclusion: Our findings indicated that breast cancer incidence peaks in the age of 45 in Iranian women, which is a decade earlier compared to the Western world. The period effect in 2015-2017 can be explained by the fact that in 2014, the former Iranian pathology-based cancer registry was upgraded to a population-based cancer registry, which resulted in improved coverage of cancer registry and case finding.