Multifocality Is not an Independent Prognostic Factor in Papillary Thyroid Cancer: A Propensity Score-Matching Analysis

Background: Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy. Despite its low mortality rate, the disease has a recurrence rate of up to 30%. The mainstay of treatment for PTC is surgery, followed by radioiodine ablation and thyroxine therapy in appropriately selected patients. PTC can appear as a unifocal solitary tumor, but also as two or more anatomically separate foci. A great deal of controversy surrounds the significance of multifocality as a prognostic factor, and it is considered a poor prognostic factor that prompts more aggressive treatment. The aim of this study was to investigate the prognostic value of tumor multifocality on disease recurrence and mortality in PTC patients. Methods: Data of 1039 consecutive PTC patients from two tertiary medical centers were reviewed. The baseline characteristics and short- and long-term outcome were analyzed to evaluate the prognostic significance of multifocal disease. The application of two different propensity score models followed multivariate analysis. Results: The median follow-up was 10.1 years, and 534 (51.4%) patients had multifocal disease and 505 (48.6%) unifocal disease. Patients with the multifocal disease were significantly older, were more frequently male, had more extrathyroidal extension, more lymph node metastases, more advanced disease (stage III/IV), and a higher American Thyroid Association recurrence risk. Multifocal PTC patients had more persistence at one year (26.6% vs. 16.4%; p < 0.001), more recurrence during follow-up (12.7% vs. 6.6%; p = 0.002), and a higher overall mortality rate (15.5% vs. 9.7%; p = 0.002). However, there were no significant differences in recurrence, last-visit persistency, and mortality rates when adjusting for confounding variables by using propensity score matching. Conclusion: This propensity score-matching study provides the best available data to support the assertion that multifocality in PTC patients is a marker of more extensive disease at presentation, but not an independent prognostic factor for long-term outcomes.