Bayesian Spatial Analysis of the Incidence Rate of Patients with Breast Cancer in Southern Iran.

Background: In the female population, breast cancer is the most common cancer and a leading cause of cancer death. This study was designed to investigate the geographical pattern of breast cancer risk in different counties of Fars province in the south of Iran from 2001 to 2018.

Methods: In this historical cohort study, data of Shiraz Population-Based Cancer Registry between 2001 and 2018 was used. The geographical variations of breast cancer incidence rate in 36 counties of Fars province were analyzed using the Bayesian spatiotemporal model.

Results: Overall, the averages of relative risk (RR), temporal trend (TT), and δ for breast cancer were 1.59, 1.025, and 0.00 in the total female population; 1.21, 1.002, and 0.00 in the young female population (under 40 years of age); and 1.54, 1.02, and 0.00 in the female population with invasive ductal carcinoma (IDC), respectively. The steady increase in RR of breast cancer and IDC during 2001-2018 was observed in most counties located in the non-central part of the Fars geographic map. Moreover, a steady increase of young breast cancer RR was observed mainly in southern regions and some northern cities of Fars province.

Conclusion: Between 2001 and 2018 in Fars province, a steady annual increase of approximately 2% was observed in the total female population for all types of breast cancer, including IDC. High-risk areas, TTs, and changing patterns of breast cancer incidence were determined in this region. Furthermore, areas with a high risk of young breast cancer were identified, which requires special attention.