ABSTRACT
Background: Differentiated thyroid cancer (DTC) is generally associated with a favorable prognosis. Its treatment requires surgery, selective use of radioiodine and levothyroxine, and its intensity must be adjusted to the initial risks of mortality and recurrence. Aim: To validate the risk of recurrence classification developed by the Chilean Ministry of Health in 2013 (MINSAL 2013), and compare it with the American Thyroid Association (ATA) 2009 and 2015 classifications. Material and Methods: Retrospective study of 362 patients with DTC aged 44.3 ± 13.4 years (84% women), treated with total thyroidectomy, selective radioiodine ablation and levothyroxine and followed for a median of 4.2 years (range 2.0-7.8). Risk of recurrence was estimated with MINSAL 2013, ATA 2009 and ATA 2015 classifications, and risk of mortality with 7th and 8th American Joint Committee on Cancer (AJCC)/TNM systems. Clinical data obtained during follow-up were used to detect structural and biochemical persistence/recurrence. Results: A mean dose of 104 ± 48 mCi radioiodine was received by 91% of patients. MINSAL 2013 classified 148 (41%), 144 (40%), 67 (19%) and 3 (1%) patients as very low, low, intermediate and high risk of recurrence, respectively. Forty-five (12.4%) patients had persistence or recurrence during follow-up: 33 structural and 12 biochemical. Rates of persistence/recurrence on each category of MINSAL 2013 were 4.1%, 7.6%, 37.3% and 100%, respectively (p < 0.01). Areas under Receiver Operating Characteristic curves for persistence or recurrence of MINSAL 2013, ATA 2009 and ATA 2015 were 0.77 vs 0.73 vs 0.72, respectively. Conclusions: MINSAL 2013 classifies appropriately DTC patients and estimates correctly their risk of persistence or recurrence.