Density incidence and trend of breast cancer in Iran

Background:Iran as a Middle Eastern country has a low, yet increasing incidence of breast cancer. Moreover it has the highest rank among all cancers in women and it is accountable for about 25 % of all cancers in women.in this study, our objectives are estimation of incidence and trend of breast cancer during thirty years in Isfahan,Iran. Methods:This is a retrospective cohort study.The study consists of 2 phases. The first phase was conducted in 4 major mammographic screening centers of Isfahan between 2012-2014. During this period every women who has been referred to one of these centers were included in the study. We conducted a questionnaire based survey assessing different risk factors of breast cancer alongside with demographic features and the report of their mammogram. The questionnaires were filled out by trained technicians for each patient. The final sample size was equal to 7807.In the second phase for endorsement of the malignant cases(1187 cases), we followed up all of their information in pathology departments and the cancer registry system. Cancer registry system has been established in Iran more than 3 decades ago and it actively collects and records all of the information of new cases of cancer from pathology laboratories and hospitals. According to the cancer registry system,our malignant cases were born between 1925-1990 and the occurrence of breast cancer was between 1980-2010.For calculation of density incidence, person-years at risk were calculated by using current age of the patient and age at the diagnosis of breast cancer according to cancer registry data. The results are reported as incidence rates and  Age-Specific (crude) incidence and Age-Adjusted  incidence rate per 100,000 person-years. Direct method of standardization using the world standard population as the reference was applied.Standardized incidence ratios (SIRs) were calculated, and significantly excess cancer incidence was determined by calculating a one-sided Poisson probability.Ninety-five percent confidence intervals (CIs) for the SIRs were calculated using Byar’s approximation.results:Mean age at diagnosis of cancer was 48.3±8.2,During 3 decades the incidence rate increased from 8.5 up to 40.4 /100000 /year. Discussion: This shows near 5 times increase in the incidence of breast cancer during 3 decades, in contrast to many western countries which have experienced much lower increase or even decrease in the incidence of breast cancer.