Identification and optimal postsurgical follow-up of patients with very low-risk papillary thyroid microcarcinomas

Papillary Thyroid Cancer Study Group .

Durante C , Attard M , Torlontano M , Ronga G , Monzani F , Costante G , Ferdeghini M , Tumino S , Meringolo D , Bruno R , De Toma G , Crocetti U , Montesano T , Dardano A , Lamartina L , Maniglia A , Giacomelli L , Filetti S

J Clin Endocrinol Metab. 2010 Nov;95(11):4882-8

Abstract

Most papillary thyroid microcarcinomas (PTMCs; ≤ 1 cm diameter) are indolent low-risk tumors, but some cases behave more aggressively. Controversies have thus arisen over the optimum postoperative surveillance of PTMC patients.

We tested the hypothesis that clinical criteria could be used to identify PTMC patients with very low mortality/recurrence risks and attempted to define the best strategy for their management and long-term surveillance.

We retrospectively analyzed data from 312 consecutively diagnosed PTMC patients with T1N0M0 stage disease, no family history of thyroid cancer, no history of head-neck irradiation, unifocal PTMC, no extracapsular involvement, and classic papillary histotypes. Additional inclusion criteria were complete follow-up data from surgery to at least 5 yr after diagnosis. All 312 had undergone (near) total thyroidectomy [with radioactive iodine (RAI) remnant ablation in 137 (44%) – RAI group] and were followed up yearly with cervical ultrasonography and serum thyroglobulin, TSH, and thyroglobulin antibody assays.

During follow-up (5-23 yr, median 6.7 yr), there were no deaths due to thyroid cancer or reoperations. The first (6-12 months after surgery) and last postoperative cervical sonograms were negative in all cases. Final serum thyroglobulin levels were undetectable (<1 ng/ml) in all RAI patients and almost all (93%) of non-RAI patients.

Accurate risk stratification can allow safe follow-up of most PTMC patients with a less intensive, more cost-effective protocol. Cervical ultrasonography is the mainstay of this protocol, and negative findings at the first postoperative examination are highly predictive of positive outcomes.

Comment

The excellent prognosis of unifocal PTC tumors <1cm without extra-thyroidal extension or nodes, has been frequently reported. This is especially true of incidental tumors found during the course of operation for another reason, as were 75% of the patients in this study.

After average >6 year follow up (in a retrospective analysis), all of those given (near) total thyroidectomy and RAI ablation had undetectable TG(<1ng/ml), as did 93% of those who had only surgery. The patients had annual exams including US and TG, but no WB scans unless TG was elevated. The authors state œ this long-term follow-up (median 6.7 yr) of more than 300 consecutive patients shows that, with a simple set of clinical criteria, we can reliably identify those patients with PTMC who are most likely to experience complete cures with total or near-total thyroidectomy. In these patients, who appear to represent approximately 75% of all PTMC cases, postoperative RAI remnant ablation and TSH suppression are not necessary, and the single most important component of the post-surgery surveillance protocol is cervical US performed by an experienced operator. Negative findings at the first postoperative scan are highly predictive of a favorable outcome, so yearly examinations at least after 5 yr are probably not required. Therefore, with effective risk stratification, the majority of PTMC patients can be safely followed with a protocol that is less intensive and more cost effective.

Probably few therapists would disagree with the major conclusions of the study, which supports general practice in caring for <1cm PTC tumors found incidentally at operation for another indication, and typically with some thyroid tissue left in place. However it remains to be proven that this advice (no RAI ablation, no follow up WB scans, discontinuation of TG and US after a few years, is equally applicable to patients operated on for a clinically detected <1cm nodule in an otherwise normal gland. L De Groot, MD 10 Jan 2011