Spatial heterogeneity and temporal trends of thyroid cancer incidence in Iran from 2014 to 2017

Global thyroid cancer (TC) incidence has risen sharply, yet subnational spatial and temporal patterns, particularly in middle-income contexts like Iran, remain understudied. This study investigates TC's spatial heterogeneity and temporal trends across Iran (2014-2017) to delineate high-risk clusters and guide targeted interventions. Data from the Iranian National Cancer Registry (18,336 cases) were analyzed, with age-standardized rates (ASRs) computed via direct standardization and annual percent changes (APCs) estimated using Poisson regression. Global and Local Moran's I statistics evaluated spatial autocorrelation and clustering by sex, and province. The four-year ASR in Iran was 11.1 per 100,000 (95% CI: 0-28.2), with females at 35.1 (95% CI: 27.4-42.7) versus males at 9.64 (95% CI: 5.9-13.4), reflecting a 3.6-fold sex disparity. Annual ASRs increased from 2.1 to 3.6 per 100,000 (APC: 19.6%), with females (17.6%) exceeding males (11.2%). Grade 9 tumors prevailed (88.2%), most prevalent in females (69.9%) and Yazd (14.5%), rising from 16.8% in 2014 to 28.1% in 2017. Spatial analysis identified high-high clusters in central provinces (e.g., Yazd: 36.6, Esfahan: 17.5 per 100,000) versus low-low clusters in the northeast (e.g., Semnan: 4.8). Peak incidence occurred at 50-54 years (females) and 70-74 years (males). Thyroid Cancer in Iran displays marked sex, geographic, and temporal disparities, propelled by diagnostic enhancements and environmental influences. Standardized registries and selective screening in high-risk zones (e.g., Yazd, Esfahan) are imperative to address this growing burden, aligning with precision public health strategies.