Is radioiodine administration in patients with papillary thyroid multifocal microcarcinoma unnecessary?

Abstract

SummaryRadioiodine (RAI) has played a crucial role in differentiated thyroid cancer treatment for more than 60years. However, the use of RAI administration in patients with papillary thyroid microcarcinoma (even multifocal) is now being widely discussed and often not recommended. In accordance with European consensus, and contrary to the American Thyroid Association (ATA) guidelines, we recently performed RAI thyroid remnant ablation in a patient with differentiated papillary multifocal microcarcinoma. The post-therapeutic whole-body scan and SPECT/CT revealed the real and unexpected extent of disease, with metastases to upper mediastinal lymph nodes. This finding led to the patient’s upstaging from stage I to stage IVa according to the American Joint Committee on Cancer/International Union Against Cancer criteria.Learning points131I is a combined beta–gamma emitter, thus allowing not only residual thyroid tissue ablation but also metastatic tissue imaging.RAI remnant ablation omission also means post-treatment whole-body scan omission, which may lead to disease underestimation, due to incorrect nodal and metastatic staging.RAI should be considered also in “low-risk” patients, especially when the lymph node involvement is not reliably documented.Lower administered RAI activity (30mCi, 1.1GBq) may be a workable compromise in low-risk patients, not indicated for RAI remnant ablation according to ATA guidelines.

Therapeutic Outcomes of Patients with Multifocal Papillary Thyroid Microcarcinomas and Larger Tumors

“…A higher percentage of soft tissue invasion and distant metastasis in multifocal PTMC are part of reasons with poor prognosis than that in solitary PTMC. The use of 131 I ablation for the treatment of multifocal PTMC is questioned by the European consensus and American Thyroid Association (ATA) guidelines [ 18 , 20 ]. In our study, 3.4% of multifocal PTMC had distant metastasis.…”

“…BRAF gene mutation combined with X chromosome inactivation analyses has been used to evaluate the clonal origins of tumors and has showed that bilateral, recurrent, and metastatic PTCs often arise from a single clone and that intrathyroid metastasis may play an important role in the development of bilateral tumors [ 21 ]. In contrast, assessment of multifocal thyroid tumors using genetic alteration analyses and miRNA profiling found that multifocal PTC did not necessarily evolve from single PTC progenitor foci [ 20 ]. In the clinic, different histological patterns like follicular variant and classical PTC in different thyroid lobes are not unusual.…”