Spatiotemporal Epidemiology of Female Thyroid Cancer: A Retrospective Population-Based Registry Study in the Hamadan Province, Iran (2010-2019).

[BACKGROUND] Thyroid cancer (TC) incidence varies regionally in Iran, with a notable increase observed in females. However, region-specific spatiotemporal epidemiological data are limited. This study aimed to quantify the spatiotemporal trends and geographic clustering of female TC in the Hamadan province, western Iran, from 2010 to 2019.

[METHODS] Female TC cases from the Hamadan province were obtained from the population-based cancer registry. County-level standardized incidence ratios (SIRs) were calculated to adjust for differences in population size, and were smoothed using a hierarchical Bayesian spatial smoothing model that accounts for spatial and temporal dependence. Temporal trends were analyzed using joinpoint regression. Spatiotemporal clusters were identified using space-time scan statistics.

[RESULTS] The incidence of female TC showed an average annual increase of 14.5% (Average annual percent change [AAPC]: 14.5, 95% confidence interval: 4.7 to 25.3; <0.001) from 2010 to 2019 in the Hamadan province. The smoothed SIRs indicated increasing trends in northern and central counties, including Hamadan, Asadabad, Famenin, Razan, and Tuyserkan, while decreasing trends were observed in southern counties such as Nahavand and Malayer. A significant high-risk spatiotemporal cluster was identified in the Hamadan county during 2018-2019 (observed-to-expected cases ratio: 2.24, <0.001), and a low-risk cluster was detected in Nahavand, Malayer, and Tuyserkan from 2010 to 2013 (0.51, <0.001).

[CONCLUSION] This study revealed significant spatiotemporal heterogeneity in female TC incidence in the Hamadan province. Identification of high-risk clusters provides an evidence base for targeted preventive measures and health resource allocation.