ECE2017 Oral Communications Thyroid Cancer (5 abstracts)
1KU Leuven, Leuven, Belgium; 2Belgian Cancer Registry, Brussels, Belgium; 3General Hospital Sint Jan, Bruges, Belgium.
Background: In Belgium, lower thyroid cancer incidence most pronounced for microcancers (T1a) is present in the North compared to the South. This variation is paralleled by differences in clinical practice: in the North less thyroid surgery is performed, more surgery is preceded by fine needle aspiration (FNA), and more patients with a final cancer diagnosis (20042006) underwent a presurgical FNA or a lymph node dissection (LND) at fist surgery.
Aim: To study 1/ the evolution in the use of FNA and LND, and 2/ the weight of T1a non-thyrotoxic thyroid glands in a recent thyroid cancer cohort.
Methodology: Population-based retrospective study, using data from the Belgian Cancer Registry (including case-by-case study of pathology protocols) and Belgian Healthcare Insurance database for differentiated thyroid cancer (DTC) cases diagnosed between 2009 and 2011 (n=2659).
Results: Linkage of both databases resulted in 2557 DTC cases (96%). In the North a higher proportion of DTC cases underwent FNA before surgery: 62.3%[95%CI 58.3;66.3] compared to 33.6%[95%CI 29.3;39.9] in the South (P<0.0001), confirming geographical differences. A positive trend for FNA was observed in the period 20042012, at national and regional level, especially in the South. The execution of LND during first thyroid surgery was proportionally higher in the North (24.3%[95%CI 20.6;28.0]) compared to the South (15.3%[95%CI 12.0;18.7], P<0.0001), without temporal trend. Finally, in the subgroup of T1a DTC cases considered to be mainly incidental findings the mean thyroid weight was 57.7±52.1 g in the North, compared to 37.99±29.1 g in the South (P<0.0001).
Conclusion: In the present cohort, more FNA precedes thyroid cancer diagnosis, according to international guidelines. However, geographical differences clearly persist. A lower thyroid weight is present in DTC T1a in the South. These findings support the alignment of a higher thyroid cancer incidence with a lower threshold for thyroid surgery in case of nodular disease, strongly suggesting overdiagnosis.