Active surveillance for low-risk papillary thyroid microcarcinomas

: The active surveillance of low-risk papillary thyroid microcarcinomas (PTMCs) was started at Kuma Hospital (Kobe, Japan) in 1993 and was then adopted widely, especially after the publication of the 2015 guidelines by the American Thyroid Association (ATA). The data collected at Kuma Hospital indicate that at the 10-year observations, the incidence of enlargement ≥ 3 mm was only 8.0% and that of the novel appearance of node metastasis was 3.8%. None of the patients showed distant metastasis or died of thyroid carcinoma. A portion of the patients underwent conversion surgery for various reasons, including disease progression, but no patients showed life-threatening recurrence/metastasis or died of thyroid carcinoma not only when they underwent active surveillance but also after they received conversion surgery. In contrast to clinical papillary thyroid carcinoma (PTC), PTMCs of elderly patients were less progressive than those of middle-aged and young patients, indicating that elderly patients are ideal candidates for active surveillance. PTMCs in young patients are the most progressive, but based on the estimated lifetime probability, >50% and >75% of patients in their 20s and 30s, respectively would not require conversion surgery during their lifetime, indicating that young patients can be candidates for active surveillance. Several studies from other institutions [including Cancer Institute Hospital (Tokyo) and foreign institutions] have been published, and all of them reported very favorable patient outcomes. Active surveillance can avoid the adverse events of immediate surgery and is more economical than immediate surgery (at least in Japan and Hong Kong). We can therefore conclude that active surveillance is suitable for the first-line management of PTMCs. 12