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. 2020 Jan;9(1):32-39.
doi: 10.1159/000504046. Epub 2019 Nov 21.

The Impact of Regional Variation in Clinical Practice on Thyroid Cancer Diagnosis: A National Population-Based Study

Brigitte Decallonne  1 , Annick Van den Bruel  2 , Gilles Macq  3 , Nathalie Elaut  3 , Harlinde De Schutter  3
Affiliations

The Impact of Regional Variation in Clinical Practice on Thyroid Cancer Diagnosis: A National Population-Based Study

Brigitte Decallonne et al. Eur Thyroid J. 2020 Jan.

Abstract

Objective: Regional variation in thyroid cancer incidence in Belgium, most pronounced for low risk cancer, was previously shown to be related to variation in clinical practice, with higher thyroid surgery rates and lower proportions of preoperative fine-needle aspiration (FNA) in regions with high thyroid cancer incidence (period 2004-2006). The objective of this study was to investigate regional thyroid cancer incidence variation in relation with variation in thyroid surgery threshold in a more recent Belgian thyroid cancer cohort.

Methods: A population-based cohort of thyroid cancer patients that underwent a (near) total thyroidectomy in the period 2009-2011 (n = 2,329 patients) was identified and studied by linking data from the Belgian cancer registry and the Belgian health insurance companies, and case-by-case study of the pathology protocols. The execution of preoperative FNA and the thyroid resection specimen weight were compared between high and low thyroid cancer incidence regions. Thyroid weight in the pT1a-restricted group was studied as a proxy for surgical threshold for benign nodular goiter. Furthermore, time trend analyses were performed for the execution of FNA for the period 2004-2012.

Results: Although a lower proportion of FNA in the high thyroid cancer incidence region persisted in the period 2009-2011 (41.2% [31.9-50.9] vs. 72.9% [64.9-79.7] in the low-incidence region (LIR), p < 0.001), a positive time trend was observed for the period 2004-2012. The median thyroid surgical specimen weight was lower in the high incidence region compared to the LIR (27.0 g [IQR 18.0-45.3] vs. 36.0 g [IQR 22.0-73.0], p < 0.0001), and this finding was corroborated in the pT1a-restricted group.

Conclusion: Interregional differences in use of FNA and surgical thyroid specimen weight are consistent with an inverse relation between thyroid cancer incidence and thyroid surgery threshold, carrying risk for overdiagnosis.

Keywords: Fine-needle aspiration; Incidence; Overdiagnosis; Thyroid cancer; Thyroid weight.

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Conflict of interest statement

There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Figures

Fig. 1
Fig. 1
Flow diagram for patient selection, identification of surgery, identification of FNA performance, evaluation of thyroid specimen weight. aIdentified via BCR; bidentified via reimbursement codes (health insurance companies); cassignment of region based on region of surgery; dbased on pathology report, with exclusion of preoperative thyrotoxicosis identified by reimbursement codes. DTC, differentiated thyroid cancer; FNA, fine-needle aspiration; LIR, low-incidence region; HIR, high-incidence region.
Fig. 2
Fig. 2
a Map of Belgium and its regions. b The incidence of thyroid cancer, being lower in the Northern region Flanders as compared to the Southern region Wallonia (further designated as, respectively, LIR and HIR). c–e The incidence of thyroid cancer (white bars represent LIR, dark bars represent HIR) by histological type (c) and T category (d), and the incidence of T1 PTC (e). All data represent age-standardized incidence rates, using the European Standard Population (number per 100,000 person years); based on BCR database where region corresponds to the region of residence, for incidence years 2009–2011. f Proportion of FNA before surgery in DTC patients without prior thyrotoxicosis for LIR and HIR, for the period 2004–2012. * p < 0.05, ** p < 0.001. LIR, low-incidence region; HIR, high-incidence region; BCR, Belgian cancer registry.
See this image and copyright information in PMC

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