Background: Prospective trials of active surveillance (AS) have shown progression rates of only about 10% in patients with low-risk papillary microcarcinoma (PMC, cT1aN0M0) of the thyroid. Previous studies demonstrated that younger age and weaker calcification were significant risk factors for progression during AS. However, the significance of multifocality as a prognostic factor is controversial. The aim of this study was to investigate the prognostic value of multifocality on progression of PMC while conducting AS.
Methods: Data of 571 patients (mean age: 53.1 years, 495 females) with PMC who underwent AS were reviewed. Progression of the tumor was defined as tumor size enlargement (3 mm or more in the maximum diameter on ultrasonography from the beginning of AS) and/or development of ultrasonographycally evident lymph node metastasis (LNM).
Results: After a mean of 7.6 years of observation, 49 patients (8.6%) showed tumor enlargement and 8 patients (1.4%) developed LNM. Ten-year progression rate was 12.7%. There were 115 patients (20.1%) with multifocal PMCs (2-5 lesions for each, 262 tumors in total) and 456 patients (79.9%) with unifocal disease. Age, sex and calcification pattern were not significantly different between the groups; however, patients with multifocal PMCs were more frequently accompanied with Hashimoto’s thyroiditis (46.2% vs 34.4%, p = 0.026). Between patients with multifocal and unifocal disease, there were no significant difference in 10-year rate of tumor enlargement (7.0% vs 11.2%, p = 0.13), LNM development (2.4% vs 1.1%, p = 0.27) and progression (14.8% vs 12.2%, p = 0.51). Eventually, 10 patients (8.7%) with multifocal PMCs underwent surgery and 9 needed to have total thyroidectomy, although 7 were still T1N0M0 low-risk cancer.
Conclusions: Even patients with multiple PMCs (cT1amN0M0) are thought to be good candidates for AS and most of them could avoid total thyroidectomy thanks to the policy.