The knowledge on thyroid cancer biology has grown over the past decade. Thus, diagnostic and therapeutic strategies to manage thyroid cancer are rapidly evolving. With new insights into tumor biology and cancer genetics, several novel therapies have been approved for the treatment of thyroid cancer. Tyrosine kinase inhibitors (TKIs), such as lenvatinib and sorafenib, have been successfully utilized for the treatment of radioactive iodine (RAI)-refractory metastatic differentiated thyroid cancer (DTC). In addition, pretreatment with mitogen-activated protein kinase (MAPK) inhibitors (trametinib and selumetinib) has been shown to restore RAI avidity in previously RAI-refractory DTCs. Local therapies, such as external beam radiation and radiofrequency/ethanol ablation, have also been employed for treatment of DTC. Vandetanib and cabozantinib are the two TKIs currently approved by the Food and Drug Administration (FDA) for the treatment of medullary thyroid cancer (MTC). Other novel therapies, such as peptide receptor radionuclide therapy and carcinoembryonic antigen (CEA) vaccine, have also been utilized in treating MTC. Ongoing trials on selective rearranged-during-transfection (RET) protooncogene inhibitors, such as LOXO-292 and BLU-667, have demonstrated promising results in the treatment of metastatic MTC resistant to non-selective TKIs. The FDA-approved BRAF/MEK inhibitor combination of dabrafenib and trametinib has revolutionized treatment of BRAFV600E mutation positive anaplastic thyroid cancer. Several other emerging classes of medications, such as gene fusion inhibitors and immune checkpoint inhibitors, are being actively investigated in several clinical trials. In this review, we describe the molecular landscape of thyroid cancer and novel targeted therapies and treatment combinations available for the treatment of metastatic thyroid cancer.

Background and Objective Recombinant human thyrotropin (rhTSH) is currently not FDA-approved for the treatment of high-risk patients with differentiated thyroid cancer (DTC). The goal of our study was to compare the outcomes in higher risk patients with metastatic DTC prepared for radioiodine (RAI) therapy with rhTSH versus thyroid hormone withdrawal (THW). Methods Retrospective chart review of patients with metastatic DTC in follow-up at MedStar Washington Hospital Center and MedStar Georgetown University Hospital from 2009 to 2017. Patients were divided according to their preparation for RAI therapy, with assessment of progression free survival (PFS) and overall survival (OS). Results Fifty-five patients with distant metastases (16 men, 39 women) were prepared for RAI therapy exclusively either with rhTSH (n= 27) or with THW (n= 28). There were no statistically significant differences between the groups regarding clinicopathological features and history of RAI therapies. The median follow-up time for patients with rhTSH-aided therapies was 4.2 yr (range 3.3 – 5.5 yr) and for patients with THW-aided therapies was 6.8 yr (range 4.2- 11.6 yr) (p=0.002). Multivariate analysis showed that the method of TSH stimulation was not associated with a difference in PFS or OS. Conclusion As has been shown previously for low-risk DTC, this study indicates that the mode of preparation for RAI therapy does not appear to influence the outcomes of patients with metastatic DTC. PFS and OS were similar for patients with THW-aided or rhTSH-aided RAI therapies.

BackgroundLutetium 177 (177Lu) - DOTATATE is a form of peptide receptor radionuclide therapy (PRRT) utilized in the treatment of neuroendocrine tumors. Data on 177Lu-DOTATATE-induced thyroid dysfunction is limited.Case DescriptionA 29-year-old male with SDHB positive metastatic paraganglioma enrolled under the 177Lu-DOTATATE trial (NCT03206060) underwent thyroid function test (TFT) evaluation comprised of thyroid stimulating hormone (TSH) and free thyroxine (FT4) immunoassay measurements per protocol prior to 177Lu-DOTATATE therapy. The TSH was suppressed [<0.01 µIU/ml (0.27–4.2 µIU/ml)], and FT4 was normal [1.3 ng/dl (0.9–1.7 ng/dl)]. The TSH receptor antibody and thyroid stimulating immunoglobulin index were undetectable [<1 IU/L (≤1.75 IU/L), and <1 (≤1.3) respectively], while the anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies were elevated [605 IU/ml (0.0–34.9 IU/ml), and 178 IU/ml (0.0-40.0 IU/ml) respectively]. Mass spectrometry on a stored (-80°C) plasma sample obtained one-month pre-PRRT revealed elevated total triiodothyronine (TT3) [235 ng/dl (65–193 ng/dl)] and FT4 [3.9 ng/dl (1.2–2.9 ng/dl)] levels. The patient was diagnosed with Hashimoto’s thyrotoxicosis. However, the patient was asymptomatic. One month after the first dose of 200mCi 177Lu-DOTATATE, the patient noted fatigue and a 2.6 Kg weight gain. The TSH (73.04 µIU/ml), anti-TPO antibodies (>1,000 IU/ml), and anti-Tg antibodies (668 IU/ml) had substantially increased, with reductions in FT4 (0.3 ng/dl) and TT3 [54 ng/dl (87–169 ng/dl)]. Diagnostic gallium 68 - DOTATATE positron emission tomography-computed tomography performed prior to 177Lu-DOTATATE treatment revealed diffuse thyroid uptake. Post-therapy single-photon emission computed tomography also revealed diffuse uptake of 177Lu-DOTATATE in the thyroid gland. Levothyroxine therapy was initiated, and the patient’s symptoms resolved.SummaryWe report, for the first time, a patient with asymptomatic primary hyperthyroidism who rapidly developed symptomatic primary hypothyroidism 1 month after 177Lu-DOTATATE therapy, accompanied by marked changes in TFTs and thyroid auto-antibody titers, with functional imaging evidence of diffuse uptake of 177Lu-DOTATATE in the thyroid gland.ConclusionsThyroid dysfunction can be associated with PRRT. Thyroid uptake patterns on pre-treatment diagnostic somatostatin analog scans might predict individual susceptibility to PRRT-associated TFT disruption. Therefore, periodic evaluation of TFTs should be considered in patients receiving PRRT.