Introduction: Differentiated thyroid carcinoma (DTC) has generally a good prognosis and is associated with prolonged survival. A minority of patients may have persistent disease and rarely aggravation during f/u. We investigated factors which may influence the persistence of disease in patients who had undergone ablation with I131.
Patients and methods: 903 DTC patients were referred in our center from 1968 to 2012. Five hundred and forty-one (22.4% males) underwent thyroid remnant ablation and were followed-up for 144 years (7.9±8.4 years). Of those 344 (65.6%) showed remission during the 12 month Tg-stimulation test (Tg ≤1.0 ng/ml). Most of those who showed disease persistence (Tg >1.0 ng/ml) underwent repeated treatments (>1 surgery and/or repeat I131 administration), while 39.1% finally showed remission (Group 1). Those with disease persistence were further divided in three subgroups according to stimulated Tg during f/u: Group 2: low-Tg (≤5 ng/ml, no clinical aggravation (CA), n=47, 23.9%), Group 3: high-Tg (>5 ng/ml, no CA, n=50, 25.4%) and Group 4: CA-group (n=23, 11.7%).
Results: Patients with 12 month remission of disease had more frequently previous history of autoimmunity (P=0.008). Men had less frequently remission at f/u and more frequently CA compared to women (26.3 vs 44.3%, 19.3 vs 8.6%, P=0.004). Group 1 had more frequently positive thyroid auto antibodies at diagnosis (Group 1: 72.7%, Group 2: 11.1%, Group 3: 12.5%, Group 4: 0%, P=0.003), and microDTCs (<1.0 cm), (28.6, 11.8, 12.5, 0%, P=0.002), less frequently lymph-node involvement (35.4, 62.8, 57.1, 84.2%, P<0.001), soft-tissue involvement (12.1, 8.6, 29.8, 52.9%, P=0.002), and distant metastases at diagnosis (0, 10, 8, 60%, P=0.003). More aggressive histological type was more frequently observed in Group 4 (P<0.001). No differences in multifocality, family DTC history and type of first surgery were observed between groups. Age at diagnosis, tumor size and Tg levels at the time of the first ablation were higher in groups 3 and 4 (P<0.04, MannWhitney).
Conclusion: In addition to classical favourable prognostic factors such as smaller size and lack of invasive features, pre-existing autoimmune thyroid disease may be associated with early remission in patients with DTC.