Multifocality and Progression of Papillary Thyroid Microcarcinoma During Active Surveillance

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Prospective trials of active surveillance (AS) have shown low rates of progression in low‐risk papillary thyroid microcarcinoma (PTMC; T1aN0M0). However, the significance of multifocality as a prognostic factor remains controversial.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Data from 571 patients (mean age, 53.1 years; 495 females) who underwent AS were reviewed. PTMC was unifocal in 457 patients (80.0%) and multifocal in 114 patients (20.0%), with 2–5 lesions each (261 tumors in total). Tumor progression was defined as tumor size enlargement ≥ 3 mm and/or development of clinically evident lymph node metastasis (LNM).</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>After a mean duration of AS of 7.6 years, 53 patients (9.3%) showed tumor enlargement and 8 patients (1.4%) developed LNM. The 10‐year progression rate was 13.1%. Age, sex, and calcification pattern did not differ significantly between uni‐ and multifocal diseases. However, anti‐thyroglobulin antibody and/or anti‐thyroid peroxidase antibody was more frequently positive with multifocal PTMCs (46.7%) than with unifocal disease (34.4%, <jats:italic>p = </jats:italic>0.024). Patients with uni‐ and multifocal disease showed no significant differences in 10‐year rate of tumor enlargement (11.4% vs. 14.8%), LNM development (1.1% vs. 2.4%), or progression (12.4% vs 15.9%). Multivariate analysis of predictors for progression showed multifocality was not a significant risk factor (odds ratio, 1.45; 95% confidence interval, 0.79–2.54; <jats:italic>p = </jats:italic>0.22). Eventually, 9 patients (7.9%) with multifocal PTMCs underwent surgery and 7 needed total thyroidectomy, although 7 still showed T1N0M0 low‐risk cancer.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Even patients with multiple PTMCs (T1amN0M0) are good candidates for AS. Many patients can avoid total thyroidectomy and subsequent surgical complications.</jats:p></jats:sec>