editorials October 01, 2019 October 01, 2019

Active surveillance of papillary thyroid microcarcinomas in South America: Are we ready?

DOI: 10.20945/2359-3997000000180

Active surveillance is defined as a strategy for treating a medical condition that involves a period of waiting and regular testing, rather than immediate treatment, such as surgery. In previous years, active surveillance (AS) of papillary thyroid microcarcinomas (mPTC; tumors with less than 1.0 cm) has been the focus of discussion worldwide, notably in the context of the epidemic of thyroid carcinomas diagnosed by neck imaging exams (). This practice was initially proposed in 1993 by Miyauchi and cols. and, recently, the Japanese group reported their experience in AS of 1235 patients diagnosed with mPTC at Kuma Hospital (). Between 1993 and 2011, patients with low-risk mPTC chose observation without immediate surgery. They were followed periodically with ultrasound examinations. It was set three parameters for the evaluation of PTMC progression: (i) size enlargement, (ii) novel appearance of lymph-node metastasis, and (iii) progression to clinical disease (tumor size reaching 12 mm or larger, or novel appearance of nodal metastasis). The proportion of patients with mPTC progression was lowest in the old patients and highest in the young patients. The reported outcomes are excellent: 8% tumor enlargement greater than 3 mm and 3.8% of novel lymph nodes metastases in a 10 years follow-up period. Such promising experiences have also been recently reported by other groups, mainly in the US () and Korea ().

In this issue, two articles discuss the overdiagnosis of thyroid nodules and the active surveillance in mPTC as an alternative treatment in South American patients. In an interesting study, Smulever and Pitoia () reported their experience in AS of mPTC in a Latin American reference center. The authors have proposed AS for those patients with mPTC who underwent fine needle aspiration biopsy (FNAB) procedure with Bethesda category V and VI results. The inclusion criteria were: the presence of a single nodule; tumor size ≤ 1.5 cm in maximal diameter; absence of clinical or radiological evidence of extrathyroidal extension, invasion of local structures, regional or distant metastasis. The authors pointed out that only 25% of 136 patients eligible for AS accepted this approach, and about 10% of these subjects abandoned AS, mainly due to their anxiety about the disease. However, the favorable outcomes of those patients that did not undergo surgery were similar to those previously reported aforementioned, with tumor enlargement occurring in only 17% of the cases and no lymph or distant metastases being diagnosed in a median 4.6 years of follow-up. There are no features that differentiate patients with stable tumors from those with increased tumor (≥ 3 mm).

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