Trends in incidence and mortality of thyroid carcinoma in The Netherlands between 1989 and 2003: correlation with thyroid fine-needle aspiration cytology and thyroid surgery.

Abstract

A persistent increase in incidence of thyroid carcinoma (TC) has been reported worldwide. The aim of our study was to assess trends in incidence and mortality of TC in The Netherlands between 1989 and 2003 and to examine whether these trends correlate with changes in diagnostic practices such as changes in the number of fine needle aspiration biopsies (FNAB) and/or thyroid surgeries. Population-based incidence and mortality data were retrieved from the Netherlands Cancer Registry. Data concerning FNAB and thyroid surgeries were obtained through the nationwide network and registry of histo- and cytopathology in The Netherlands (PALGA). Overall, the incidence of TC remained unchanged. However, there was a slight increase in incidence of papillary TC of 2.1% per year (p < 0.001) particularly in stage I tumors, possibly, in part, because of a marked increase in use of FNAB. Appropriate iodine intake, reduced radiation exposure and a more conservative diagnostic approach toward asymptomatic thyroid nodules may explain why this increase is less pronounced compared to other countries. Incidence of other subtypes of TC decreased (follicular TC, 1.3% per year, p = 0.02 and anaplastic TC, 7.1% per year, p = 0.006) or remained unchanged (medullary TC). The number of FNABs per year progressively increased from 1,093 in 1989 to 4,123 in 2003, whereas the number of thyroid surgeries decreased from 3,419 in 1989 to 2,825 in 2003. The mortality rates decreased by 2.3% per year (p = 0.01). The decrease in incidence of both follicular and anaplastic TC is assumed to be largely responsible for the decrease in TC mortality rates.