Thyroid cancer epidemiology in Ireland from 1994 to 2019 – Rising diagnoses without mortality benefit

Abstract

BackgroundThe epidemiology and management of thyroid cancer has changed radically in the recent past, with rising international incidence of early-stage papillary thyroid cancer (PTC) in particular. In this paper, we review the epidemiology of thyroid cancer in Ireland. MethodsA retrospective cohort study of National Cancer Registry of Ireland data, 1994–2019. ResultsRecords from 4158 patients were analysed. 73 % (n = 3040) were female. The average age was 50.4 years. Patient sex did not change over time (p = 0.662), while age decreased significantly (p < 0.0001). The most common diagnoses were PTC (n = 2,905, 70 %) and follicular thyroid carcinoma (n = 549, 13 %). Incidence rose over threefold (1.8–6.2 cases/100000 person-years). The incidence of T1 PTC rose over twelvefold (0.169–2.1 cases/100000 person-years), while the incidence of stage III and IV disease did not change significantly. Five-year disease-specific survival (DSS) was 85 % and varied significantly by diagnosis – 97 % for PTC versus 5 % for anaplastic thyroid carcinoma. Survival did not change significantly over time. Male sex was a risk factor for more advanced disease (p < 0.0001) but did not independently predict overall survival except in PTC (HR 1.6, p = 0.03). The use of radioactive iodine declined markedly from 49 % to 12.5 %. RAI improved DSS for PTC patients aged over 55 years (p = 0.02) without a notable effect on survival for those under 55 years (p = 0.99). ConclusionThe epidemiology and management of thyroid cancer in Ireland has changed dramatically in a manner reflective of international trends.