The impact of overdiagnosis on thyroid cancer epidemic in Italy,1998-2012

Aims: In Italy, incidence rates of thyroid cancer (TC) are among the highest world- wide with substantial intracountry heterogeneity. The aim of the study was to examine time trends of TC incidence in Italy and to estimate the proportion of TC cases potentially attribut- able to overdiagnosis. Methods: Data on TC cases reported to Italian cancer registries during 1998e2012 aged <85 years were included. Age-standardised incidence rates (ASR) were computed by sex, period, and histology. TC overdiagnosis was estimated by sex, period, age, and Italian region. Results: In Italy between 1998e2002 and 2008e2012, TC ASR increased of 74% in women (from 16.2 to 28.2/100,000) and of 90% in men (from 5.3 to 10.1/100,000). ASR increases were nearly exclusively due to papillary TC (þ91% in women, þ120% in men). In both sexes, more than three-fold differences emerged between regions with highest and lowest ASR. Among TC cases diagnosed in 1998e2012 in Italy, we estimated that overdiagnosis accounted for 75% of cases in women and 63% in men and increased over the study period leading to overdiagnosis of 79% in women and 67% in men in 2008e2012. Notably, overdiagnosis was over 80% among women aged <55 years, and substantial variations were documented across Italian regions, in both genders. Conclusion(s): Incidence rates of TC are steadily increasing in Italy and largely due to over- diagnosis. These findings call for an update of thyroid gland examination practices in the asymptomatic general population, at national and regional levels. a 2018 Elsevier Ltd. All rights reserved.