Endocrine Abstracts

Introduction: In recent years, micro papillary thyroid carcinomas (mPTCs; ≤1.0 cm) are increasingly diagnosed. Although clinical course is usually favourable, disease persistence may occur and multiple treatments needed. We examined factors that could be predictors of clinical behaviour and disease persistence.

Patients and methods: 478 mPTC patients (78.9% females) followed-up for 0.6–10 years were classified according to tumour size in group 1: 0.1–0.2 (n=85), group 2: 0.3–0.4 (n=81), group 3: 0.5–0.6 (n=96), group 4: 0.7–0.8 (n=79), and group 5: 0.9–1.0 cm (n=137).

Results: Median age at diagnosis, sex and histological type did not differ between subgroups. Capsular and lymph node invasion as well as soft tissue involvement was more frequent with increasing tumor size (P<0.001). Multifocality and distant metastasis at diagnosis was similar. Patients with mPTCs ≥0.7 cm (groups 4 and 5) underwent more frequently lymph node dissection (P=0.009) as well as ablation with ¹³¹I (P<0.001). In those who underwent thyroid ablation, disease remission during the 12-month Tg-stimulation (Tg ≤1.0 ng/ml) was less frequent in group 5 (group 1: 85.7%, group 2: 88.2%, group 3: 92.7%, group 4: 85.4%, and group 5: 69.1%, P=0.007). However, after multiple treatments (>1 surgeries and/or repeated ¹³¹I administration) the disease outcome did not differ significantly. The 10-year probability of lack of progression of disease did not differ between groups (100% vs 97% vs 100%, vs 100%, vs 95.5%, respectively, P=0.3). In Cox proportional hazard analysis when age at diagnosis, tumour size, lymph node, capsular and tissue invasion were taken into account the only predictor for disease progression was lymph node invasion (HR 0.039, 95% CI 0.004–0.379, P=0.005). Similar results were found when only those who underwent ablation with ¹³¹I were examined. 10.3% of patients with lymph node invasion showed disease progression; all belonged to group 5 (P=0.038, Pearson χ²).

Conclusions: Although, patients with tumours ≥0.9 cm have more frequently disease persistence, the final outcome is similar in all mPTC groups. Lymph node invasion may be the only factor predicting disease progression in mPTCs.