Scoring system for predicting recurrences in patients with papillary thyroid microcarcinoma.

CONTEXT Papillary thyroid microcarcinomas (PMC) defined as tumors ≤10 mm in diameter (including pT1a and pT3 according to the latest pTNM classification) have good prognosis, although recurrence is possible. Clinicians are interested in using a scoring system for predicting recurrences. OBJECTIVE To identify the prognostic factors for recurrence in patients with PMC and to develop a scoring system based on lymph node involvement, multifocality, and sex. To determine the impact of extrathyroidal invasion (ETI) and a threshold value for analyzing multifocality. METHODS Single-center retrospective study of a cohort of 1669 patients with PMC managed from 1960 to 2007. The Kaplan-Meier survival rate and prognostic factors of events were analyzed using log-rank tests and uni- and multivariate Cox model-based analyses. A scoring system was proposed. RESULTS Sixty-eight recurrences were observed. Initial lymph node metastases (P=0.0001), multifocality (P=0.05), and male sex (P=0.01) were significantly associated with recurrence, although there was a period effect (after 1990). PMC size was not a significant variable. Our scoring system allows us to separate patients into three risk groups according to their recurrence-free probability. For PMC Nx patients, total foci size of multifocal tumors >20 mm was significantly associated with recurrence (P<0.0001). Radioiodine (RAI) ablation was associated with better outcome only in PMC with ETI. CONCLUSION Our scoring system classifies recurrence risk. In PMC Nx patients, multifocality is important in planning therapeutic strategies. Recurrence probability of pT3 PMC appears lower if RAI ablation is performed.