Active surveillance for papillary thyroid microcarcinoma in a population with restrictive diagnostic work-up strategies.

Background The worldwide incidence of papillary thyroid carcinoma (PTC) has increased. Efforts to reduce overtreatment follow two parallel approaches; limiting diagnostic work-up of low-risk thyroid nodules, and pursuing active surveillance (AS) after diagnosis of the mPTC. However, most studies on AS have been performed in countries with a relatively high proportion of overdiagnosis and thus incidental mPTC. The role of AS in a population with a restrictive diagnostic work-up protocol for imaging and FNA remains unknown. Therefore, the aim of this study is to describe the proportion and characteristics of patients with mPTC in the Netherlands and to describe the potential candidates for AS in a situation with restrictive diagnostic protocols since 2007. Methods All operated patients with a mPTC in the Netherlands between 2005 and 2015 were identified from the Netherlands Cancer Registry database. Three groups were defined: 1) mPTC with preoperative distant or lymph node metastases, 2) mPTC in pathology report after thyroid surgery for another indication, 3) patients with a preoperative high suspicious thyroidal nodule or proven mPTC (Bethesda 5 or 6). Only patients in Group 3 are potential candidates for AS. Results A total of 1018 mPTC patients were identified. Group 1 consisted of 152 patients with preoperatively discovered metastases. Group 2 consisted of 667 patients of which 16 (2.4%) developed lymph node metastases. There were 199 patients in Group 3 of which 27 (13.6%) developed lymph node metastases. After initial treatment in Group 3, 3.5% (7/199) of the patients experienced recurrence. Conclusions Restrictive diagnostic work-up strategies of patients with small thyroid nodules leads to limited patients eligible for AS and a higher incidence of lymph node metastases. We believe that there is limited additive value for AS in countries with restrictive diagnostic work-up guidelines such as in the Netherlands. However, if a mPTC is encountered, AS can be offered on an individual basis.