International Consensus on the Requirements for Definitions of Complete Remission and Recurrence of Differentiated Thyroid Cancer: a Delphi Study (ICON-DTC).

[OBJECTIVE] Recurrence is a key outcome measure of treatment for differentiated thyroid carcinoma (DTC). In international guidelines and current literature, a consistent definition is lacking, which hinders comparison of treatment-related oncological outcomes. Therefore, the aim of this study was to reach international consensus among experts from all medical specialties involved in the care of patients with DTC on the essential elements minimally required for a universal definition of recurrence-serving as a first step toward developing a new, universally accepted definition of DTC recurrence.

[DESIGN] We conducted an international Delphi study.

[METHODS] A steering committee provided advice on the study protocol and Delphi rounds. Experts were identified through various scientific associations, international guidelines, ClinicalTrials.gov, our systematic review on definitions of DTC recurrence, and suggestions from the steering committee. A 3-round Delphi process was conducted to reach consensus on the minimally essential components of the definition of DTC recurrence. The initial list of components was derived from our systematic review.

[RESULTS] In total, 127 experts from all medical specialties involved in the diagnosis and treatment of DTC, representing 35 countries across 4 continents, completed 3 Delphi rounds. Thirteen key components critical for defining complete remission and recurrence of DTC were identified, following treatment with total thyroidectomy and postoperative radioiodine therapy (RIT), total thyroidectomy without RIT, and less-than-total thyroidectomy.

[CONCLUSIONS] The components identified through this international Delphi consensus can serve as the foundation for the further development of universal definitions of DTC recurrence.