Selumetinib-enhanced radioiodine uptake in advanced thyroid cancer

Current and Future Role of Tyrosine Kinases Inhibition in Thyroid Cancer: From Biology to Therapy

Thyroid cancer represents a heterogenous disease whose incidence has increased in the last decades. Although three main different subtypes have been described, molecular characterization is progressively being included in the diagnostic and therapeutic algorithm of these patients. In fact, thyroid cancer is a landmark in the oncological approach to solid tumors as it harbors key genetic alterations driving tumor progression that have been demonstrated to be potential actionable targets. Within this promising and rapid changing scenario, current efforts are directed to improve tumor characterization for an accurate guidance in the therapeutic management. In this sense, it is strongly recommended to perform tissue genotyping to patients that are going to be considered for systemic therapy in order to select the adequate treatment, according to recent clinical trials data. Overall, the aim of this article is to provide a comprehensive review on the molecular biology of thyroid cancer focusing on the key role of tyrosine kinases. Additionally, from a clinical point of view, we provide a thorough perspective, current and future, in the treatment landscape of this tumor.

Foundation One Genomic Interrogation of Thyroid Cancers in Patients With Metastatic Disease Requiring Systemic Therapy

CONTEXT

Clinical applications of genomic assessment of thyroid cancers are rapidly evolving.

OBJECTIVES, DESIGN, AND SETTING

We studied tumor samples from patients with imminently threatening and rare thyroid cancers to identify genomic alterations that might correlate with outcomes and/or be productively therapeutically targetable.

PATIENT CONTEXT

Progressive and metastatic, and/or rare, thyroid cancers were studied, 2012 to 2016, at Mayo Clinic sites.

INTERVENTION

The intervention was Foundation One tumor interrogation.

MAIN OUTCOME MEASURES

Main outcome measures included genomic alterations, patient characteristics, and overall survival.

RESULTS

Samples from 55 patients were evaluated: 20 anaplastic thyroid cancers (ATCs) (36%), 25 radioactive iodine-refractory differentiated thyroid cancers (DTCs)/poorly differentiated thyroid cancers (PDTCs) (45%; 14 papillary thyroid cancer [PTCs], 6 PDTCs, 5 Hürthle cell cancers), 8 medullary thyroid cancers (MTCs) (15%), and 2 others (a spindle epithelial tumor with thymus-like differentiation, and a primary thyroid sarcoma). Overall, 72% of DTCs, 79% of ATCs, and 75% of MTCs were deemed to have potentially productively targetable alterations. The most commonly encountered mutation was of TERT promoter (56% of DTCs, 68% of ATCs)-but this is not presently targetable. Targetable BRAFV600E mutations were found in 40% of DTCs/PDTCs (83% of PTCs) and 32% of ATCs; of MTCs, 75% had targetable RET mutations, and 25% HRAS mutations. Of patient tumors with nonmutated BRAFV600E, 53% of DTC/PDTCs and 69% of ATCs had other potentially productively targetable mutations. Genomic alterations in our series of poor prognosis metastatic DTC/PDTCs also closely resembled those seen in ATC.

CONCLUSIONS

Whereas genomic interrogation of favorable prognosis thyroid cancer seems ill advised, potentially productively targetable mutations were demonstrated in the majority of tumors from patients with metastatic thyroid cancers requiring systemic therapy, suggesting a rationale for the selective application of this technology.

New paradigms in the treatment of low-risk thyroid cancer

INTRODUCTION

Thyroid cancer is the most common endocrine malignancy. Multiple different staging systems have been introduced and used for differentiated thyroid carcinoma (DTC).

AREAS COVERED

In this literature review we provide an overview of the standard options for management of patients with low risk differentiated thyroid cancer.

EXPERT OPINION

Surgery is considered the first and most important step in managing DTC with goal to remove all the malignant foci in order to achieve cure and increase the survival with least chance of recurrence. Many studies have been conducted to determine the best surgical approaches and how aggressive surgeries should be in order to achieve the best outcomes regarding efficacy as well as safety. Radioactive iodine (RAI) therapy has also been a part of the treatment regimen and is used for different purposes with three main goals: post-surgical ablation, adjuvant therapy and persisted/recurrent disease treatment. Radiation therapy, on the other hand, is still not recommended to be used routinely in DTC because of the conflicting data of its benefit.

Management of pediatric differentiated thyroid cancer: An overview for the pediatric oncologist

Differentiated thyroid cancer (DTC) is the most common childhood thyroid malignancy. The standard of care for pediatric DTC is total thyroidectomy followed by radioactive iodine (RAI) treatment when indicated. Molecular changes and potential therapeutic targets have been recently described in pediatric thyroid cancer. Pediatric oncologists are increasingly involved in the evaluation of thyroid nodules in childhood cancer survivors and in the management of advanced thyroid cancer. In 2015, the American Thyroid Association published management guidelines for children with DTC. We provide an overview of the current standard of care and highlight available targeted therapies for progressive or RAI refractory DTC.

Kinase Inhibitors in the Treatment of Thyroid Cancer: Institutional Experience

Although most patients with thyroid cancer have a favorable clinical course, some patients develop a more aggressive type of cancer and exhibit more rapid disease progression with worse prognosis. Those patients usually exhibit mutations of proteins such as tyrosine kinase enzymes that play a significant role in regulation of tumor proliferation and spreading. Development of targeted therapies is based on the inhibition of mutated kinases which are involved in the MAPK signaling pathway. The aim of this study was to present the initial results of clinical experience with kinase inhibitors in patients with metastatic differentiated thyroid cancer (DTC), poorly differentiated thyroid cancer (PDTC), and medullary thyroid cancer (MTC) who exhibited rapid disease progression. A total of 17 adult patients (11 women, mean age 53.3 years) managed for progressive, metastatic disease were included in the study. Twelve patients with DTC and PDTC were previously tested for BRAF mutations, of whom nine that had tumor tissue negative for the BRAF V600E mutation received sorafenib, while three patients with tumors harboring the BRAF V600E mutation were treated with vemurafenib. Patients with MTC were treated with sunitinib, vandetanib, and sorafenib. Two patients with tumors harboring the BRAF mutation treated with vemurafenib showed restoration of radioiodine uptake. Most of patients showed significant improvement in disease status but of limited duration until disease progression. Although there was an improvement in progression-free survival, future research has to achieve a greater and longer-lasting response, probably by utilizing combined targeted therapy.

Pancreatic Cancer and Its Microenvironment-Recent Advances and Current Controversies

Pancreatic ductal adenocarcinoma (PDAC) causes annually well over 400,000 deaths world-wide and remains one of the major unresolved health problems. This exocrine pancreatic cancer originates from the mutated epithelial cells: acinar and ductal cells. However, the epithelia-derived cancer component forms only a relatively small fraction of the tumor mass. The majority of the tumor consists of acellular fibrous stroma and diverse populations of the non-neoplastic cancer-associated cells. Importantly, the tumor microenvironment is maintained by dynamic cell-cell and cell-matrix interactions. In this article, we aim to review the most common drivers of PDAC. Then we summarize the current knowledge on PDAC microenvironment, particularly in relation to pancreatic cancer therapy. The focus is placed on the acellular stroma as well as cell populations that inhabit the matrix. We also describe the altered metabolism of PDAC and characterize cellular signaling in this cancer.

Cellular Plasticity in Breast Cancer Progression and Therapy

With the exception of non-melanoma skin cancer, breast cancer is the most frequently diagnosed malignant disease among women, with the majority of mortality being attributable to metastatic disease. Thus, even with improved early screening and more targeted treatments which may enable better detection and control of early disease progression, metastatic disease remains a significant problem. While targeted therapies exist for breast cancer patients with particular subtypes of the disease (Her2+ and ER/PR+), even in these subtypes the therapies are often not efficacious once the patient's tumor metastasizes. Increases in stemness or epithelial-to-mesenchymal transition (EMT) in primary breast cancer cells lead to enhanced plasticity, enabling tumor progression, therapeutic resistance, and distant metastatic spread. Numerous signaling pathways, including MAPK, PI3K, STAT3, Wnt, Hedgehog, and Notch, amongst others, play a critical role in maintaining cell plasticity in breast cancer. Understanding the cellular and molecular mechanisms that regulate breast cancer cell plasticity is essential for understanding the biology of breast cancer progression and for developing novel and more effective therapeutic strategies for targeting metastatic disease. In this review we summarize relevant literature on mechanisms associated with breast cancer plasticity, tumor progression, and drug resistance.

ImmunoPET: Concept, Design, and Applications

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

Trametinib Activity in Patients with Solid Tumors and Lymphomas Harboring BRAF Non-V600 Mutations or Fusions: Results from NCI-MATCH (EAY131)

PURPOSE

Substantial preclinical evidence and case reports suggest that MEK inhibition is an active approach in tumors with BRAF mutations outside the V600 locus, and in BRAF fusions. Thus, Subprotocol R of the NCI-MATCH study tested the MEK inhibitor trametinib in this population.

PATIENTS AND METHODS

The NCI-MATCH study performed genomic profiling on tumor samples from patients with solid tumors and lymphomas progressing on standard therapies or with no standard treatments. Patients with prespecified fusions and non-V600 mutations in BRAF were assigned to Subprotocol R using the NCI-MATCHBOX algorithm. The primary endpoint was objective response rate (ORR).

RESULTS

Among 50 patients assigned, 32 were eligible and received therapy with trametinib. Of these, 1 had a BRAF fusion and 31 had BRAF mutations (13 and 19 with class 2 and 3 mutations, respectively). There were no complete responses; 1 patient (3%) had a confirmed partial response (patient with breast ductal adenocarcinoma with BRAF G469E mutation) and 10 patients had stable disease as best response (clinical benefit rate 34%). Median progression-free survival (PFS) was 1.8 months, and median overall survival was 5.7 months. Exploratory subgroup analyses showed that patients with colorectal adenocarcinoma (n = 8) had particularly poor PFS. No new toxicity signals were identified.

CONCLUSIONS

Trametinib did not show promising clinical activity in patients with tumors harboring non-V600 BRAF mutations, and the subprotocol did not meet its primary endpoint.

A Novel Tyrosine Kinase Inhibitor Can Augment Radioactive Iodine Uptake Through Endogenous Sodium/Iodide Symporter Expression in Anaplastic Thyroid Cancer

Background: Radioactive iodine (RAI) therapy is an important strategy in the treatment of thyroid cancer. However, anaplastic thyroid cancer (ATC), a rare malignancy, exhibits severe dedifferentiation characteristics along with a lack of sodium iodide symporter (NIS) expression and function. Therefore, RAI therapy is ineffective and contributes toward poor prognosis of these patients. Recently, small-molecule tyrosine kinase inhibitors (TKIs) have been used to treat thyroid cancer patients for restoring NIS expression and function and RAI uptake capacity. However, most results reported thus far are associated with differentiated thyroid cancer. In this study, we identified a new TKI and investigated its effects on cell redifferentiation, NIS function, and RAI therapy in ATC. Methods: We identified a new TKI, "5-(5-{4H, 5H,6H-cyclopenta[b]thiophen-2-yl}-1,3,4-oxadiazol-2-yl)-1-methyl-1,2-dihydropyridin-2-one" (CTOM-DHP), using a high-throughput screening system. CTOM-DHP was exposed to 8505C ATC cells at different concentrations and time points. Concentrations of 12.5 and 25 μM and an incubation time of 72 hours were chosen as the conditions for subsequent NIS promoter assays and NIS mRNA and protein expression experiments. In addition, we examined factors related to iodide metabolism after CTOM-DHP treatment as well as the signaling pathways mediating the effects of CTOM-DHP on endogenous NIS expression. RAI uptake and ¹³¹I cytotoxicity effects caused by CTOM-DHP pretreatment were also evaluated in vitro and in vivo. Results: Promoter assays as well as mRNA and protein expression analyses confirmed that NIS expression was augmented by treatment of 8505C ATC cells with CTOM-DHP. Moreover, CTOM-DHP treatment robustly increased the expression of other thyroid-specific proteins and thyroid transcription factors related to iodide metabolism. Enhancement of NIS function was demonstrated by an increase in ¹²⁵I uptake and ¹³¹I cytotoxicity. Increased endogenous NIS expression was associated with the inhibition of PI3K/Akt and MAPK signaling pathways. In vivo results also demonstrated an increase in NIS promoter activity and RAI avidity in response to CTOM-DHP treatment. Furthermore, ¹³¹I-mediated therapeutic effects preferentially improved in a tumor xenograft mice model. Conclusions: CTOM-DHP, a new TKI identified in this study, enhances endogenous NIS expression and thereby is a promising compound for restoring RAI avidity in ATC.

Bone metastases in thyroid cancer

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Osseous metastases (OMs) occur in only 4% of all thyroid cancer patients but are associated with greatly increased morbidity and mortality.

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OMs are about twice as frequent in follicular, hurthle cell, and medullary thyroid cancers as compared to papillary thyroid cancers.

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OMs are often lytic, triggered via activation of osteoclasts by tumor cells in a “vicious cycle”.

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OMs are often initially asymptomatic, but associated with eventual skeletal related events in >75%.

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Early identification of OMs, preemptive treatment with antiresorptive agents, and aggressive treatment of focal lesions before crisis are key.

Whereas preemptive screening for the presence of lymph node and lung metastases is standard-of-care in thyroid cancer patients, bone metastases are less well studied and are often neglected in thyroid cancer patient surveillance. Bone metastases in thyroid cancer are, however, independently associated with poor/worse prognosis with a median overall survival from detection of only 4 years despite an otherwise excellent prognosis for the vast majority of thyroid cancer patients. In this review we summarize the state of current knowledge as pertinent to bony metastatic disease in thyroid cancer, including clinical implications, impacts on patient function and quality of life, pathogenesis, and therapeutic opportunities, proposing approaches to patient care accordingly. In particular, bone metastasis pathogenesis appears to reflect cooperatively between cancer and the bone microenvironment creating a “vicious cycle” of bone destruction rather than due exclusively to tumor invasion into bone. Additionally, bone metastases are more frequent in follicular and medullary thyroid cancers, requiring closer bone surveillance in patients with these histologies. Emerging data also suggest that treatments such as multikinase inhibitors (MKIs) can be less effective in controlling bone, as opposed to other (e.g. lung), metastases in thyroid cancers, making special attention to bone critical even in the setting of active MKI therapy. Although locoregional therapies including surgery, radiotherapy and ablation play important roles in palliation, antiresorptive agents including bisphosphonates and denosumab appear individually to delay and/or lessen skeletal morbidity and complications, with dosing frequency of every 3 months appearing optimal; their early application should therefore be strongly considered.

Emerging Therapies for Radioactive Iodine Refractory Thyroid Cancer

OPINION STATEMENT

The landscape of treatment options for radioactive iodine refractory thyroid cancer is rapidly changing. While there are no curative options in this setting, tyrosine kinase inhibitors (TKIs) have revolutionized the management of radioiodine refractory disease to help delay progression of metastatic and life-threatening disease. Ongoing development of more selective targeted inhibitors will certainly improve medication tolerability and tumor specificity. In this review, we discuss the epidemiology of radioactive iodine refractory thyroid cancer and examine the definition of radioactive iodine refractory disease and the current systemic therapy options. We then discuss molecularly targeted strategies both approved by the FDA and currently under study in clinical trials. In particular, we examine the data relevant to specific targeted mutations in thyroid cancer. We also discuss novel approaches in development, such as immunotherapy, to the management of radioactive iodine refractory disease.

Combined tazemetostat and MAPKi enhances differentiation of papillary thyroid cancer cells harbouring BRAFV600E by synergistically decreasing global trimethylation of H3K27

Clinical efficacy of differentiation therapy with mitogen-activated protein kinase inhibitors (MAPKi) for lethal radioiodine-refractory papillary thyroid cancer (RR-PTC) urgently needs to be improved and the aberrant trimethylation of histone H3 lysine 27 (H3K27) plays a vital role in BRAF^V600E -MAPK-induced cancer dedifferentiation and drug resistance. Therefore, dual inhibition of MAPK and histone methyltransferase (EZH2) may produce more favourable treatment effects. In this study, BRAF^V600E -mutant (BCPAP and K1) and BRAF-wild-type (TPC-1) PTC cells were treated with MAPKi (dabrafenib or selumetinib) or EZH2 inhibitor (tazemetostat), or in combination, and the expression of iodine-metabolizing genes, radioiodine uptake, and toxicity were tested. We found that tazemetostat alone slightly increased iodine-metabolizing gene expression and promoted radioiodine uptake and toxicity, irrespective of the BRAF status. However, MAPKi induced these effects preferentially in BRAF^V600E mutant cells, which was robustly strengthened by tazemetostat incorporation. Mechanically, MAPKi-induced decrease of trimethylation of H3K27 was evidently intensified by tazemetostat in BRAF^V600E -mutant cells. In conclusion, tazemetostat combined with MAPKi enhances differentiation of PTC cells harbouring BRAF^V600E through synergistically decreasing global trimethylation of H3K27, representing a novel differentiation strategy.

Radiotheragnostics Paradigm for Radioactive Iodine (Iodide) Management of Differentiated Thyroid Cancer

This review of radioactive iodide treatment (RAIT) extends from historical origins to its modern utilization in differentiated thyroid cancer (DTC). The principles embedded in the radiotheragnostics (RTGs) paradigm are detailed. The diverse approaches in current practice are addressed, and this broad variability represents a major weakness that erodes our specialty's trust-based relationship with patients and referring physicians. The currently developing inter-specialty collaboration should be hailed as a positive change. It promises to clarify the target-based terminology for RAIT. It defines RAIT of post total thyroidectomy (PTT), presumably benign thyroid as 'remnant ablation' (RA). 'Adjuvant treatment' (AT) referrers to RAIT of suspected microscopic DTC that is inherently occult on diagnostic imaging. RAIT directed at DTC lesion(s) overtly seen on diagnostic imaging is termed 'treatment of known disease' (TKD). It was recently recognized that a 'recurrent' DTC is actually occult residual DTC in the majority of cases. Thyroglobulin with remnant uptake concord (TRUC) method (aka Tulchinsky method) was developed to validate that a benign remnant in the post-thyroidectomy neck bed, as quantified by the RAI uptake, is concordant with a measured thyroglobulin (Tg) level at the time of the initial post-thyroidectomy evaluation. It allows recognition of occult residual DTC contribution to post-thyroidectomy Tg. Case examples demonstrate the application of the TRUC method for a logical selection of a specific RAIT category, using imaging-guided identification and management of RAI-avid versus RAI-nonavid residual DTC, i.e. the radiotheragnostics paradigm.

New Therapies for Advanced Thyroid Cancer

Thyroid cancer is the most common endocrine cancer. The discovery of new biomarkers for thyroid cancer has significantly improved the understanding of the molecular pathogenesis of thyroid cancer, thus allowing more personalized treatments for patients with thyroid cancer. Most of the recently discovered targeted therapies inhibit the known oncogenic mechanisms in thyroid cancer initiation and progression such as MAPK pathway, PI3K/Akt-mTOR pathways, or VEGF. Despite the significant advances in molecular testing and the discoveries of new and promising therapeutics, effective treatments for advanced and metastatic, iodine-refractory thyroid cancer are still lacking. Here, we aim to summarize the current understanding of the genetic alterations and the dysregulated pathways in thyroid cancer and to discuss the most recent targeted therapies and immunotherapy for advanced thyroid cancer with a promising anti-tumor activity and clinical benefit.

Standardised quantitative radioiodine SPECT/CT Imaging for multicentre dosimetry trials in molecular radiotherapy

The SEL-I-METRY trial (EudraCT No 2015-002269-47) is the first multicentre trial to investigate the role of 123I and 131I SPECT/CT-based tumour dosimetry to predict response to radioiodine therapy. Standardised dosimetry methodology is essential to provide a robust evidence-base for absorbed dose-response thresholds for molecular radiotherapy (MRT). In this paper a practical standardised protocol is used to establish the first network of centres with consistent methods of radioiodine activity quantification. Nine SPECT/CT systems at eight centres were set-up for quantitative radioiodine imaging. The dead-time of the systems was characterised for up to 2.8 GBq 131I. Volume dependent calibration factors were measured on centrally reconstructed images of 123I and 131I in six (0.8-196 ml) cylinders. Validation of image quantification using these calibration factors was performed on three systems, by imaging a 3D-printed phantom mimicking a patient's activity distribution. The percentage differences between the activities measured in the SPECT/CT image and those measured by the radionuclide calibrator were calculated. Additionally uncertainties on the SPECT/CT-based activities were calculated to indicate the limit on the quantitative accuracy of this method. For systems set-up to image high 131I count rates, the count rate versus activity did not peak below 2.8 GBq and fit a non-paralysable model. The dead-times and volume-dependent calibration factors were comparable between systems of the same model and crystal thickness. Therefore a global calibration curve could be fitted to each. The errors on the validation phantom activities' were comparable to the measurement uncertainties derived from uncertainty analysis, at 10% and 16% on average for 123I and 131I respectively in a 5 cm sphere. In conclusion, the dead-time and calibration factors varied between centres, with different models of system. However, global calibration factors may be applied to the same system model with the same crystal thickness, to simplify set-up of future multi-centre MRT studies.

Targeted Therapy for Advanced Thyroid Cancer: Kinase Inhibitors and Beyond

The treatment of advanced thyroid cancer has undergone rapid evolution in the last decade, with multiple kinase inhibitor drug approvals for each subtype of thyroid cancer and a number of other commercially available drugs that have been studied for this indication. Although most of the US Food and Drug Administration (FDA)-approved drugs are antiangiogenic multikinase inhibitors-vandetanib, cabozantinib, sorafenib, lenvatinib-there are two FDA indications that are mutation specific-dabrafenib/trametinib for BRAF-mutated anaplastic thyroid cancer and larotrectinib for NTRK-fusion thyroid cancer. Furthermore, other mutation-specific drugs, immunotherapies, and novel strategies for advanced thyroid cancer are under investigation. Understanding the molecular basis of thyroid cancer, the drugs of interest for treatment of advanced thyroid cancer, and how these drugs can be administered safely and in the appropriate clinical scenario are the topics of this review.

Contemporary Debates in Adult Papillary Thyroid Cancer Management

An ever-increasing population of patients with papillary thyroid cancer is engaging with health care systems around the world. Numerous questions about optimal management have arisen that challenge conventional paradigms. This is particularly the case for patients with low-risk disease, who comprise most new patients. At the same time, new therapies for patients with advanced disease are also being introduced, which may have the potential to prolong life. This review discusses selected controversial issues in adult papillary thyroid cancer management at both ends of the disease spectrum. These topics include: (i) the role of active surveillance for small papillary cancers; (ii) the extent of surgery in low-risk disease (lobectomy vs total thyroidectomy); (iii) the role of postoperative remnant ablation with radioiodine; (iv) optimal follow-up strategies in patients, especially those who have only undergone lobectomy; and (v) new therapies for advanced disease. Although our current management is hampered by the lack of large randomized controlled trials, we are fortunate that data from ongoing trials will be available within the next few years. This information should provide additional evidence that will decrease morbidity in low-risk patients and improve outcomes in those with distant metastatic disease.

Treatment of Aggressive Thyroid Cancer

Although thyroid cancer generally has a good prognosis, there is a subset of patients for whom standard care (ie, treatment limited to surgery or surgery plus radioactive iodine) is either not appropriate because of the aggressive nature of their disease or not sufficient because of disease progression through standard treatment. Most of these tumors are in 3 groups: radioactive iodine-refractory differentiated thyroid carcinoma including poorly differentiated thyroid carcinoma anaplastic thyroid carcinoma, and progressive medullary thyroid carcinoma. Major classes of treatments in clinical development for these aggressive thyroid tumors include tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors, and mitogen-activated protein kinase kinase inhibitors.

Influencers on Thyroid Cancer Onset: Molecular Genetic Basis

Thyroid cancer, a cancerous tumor or growth located within the thyroid gland, is the most common endocrine cancer. It is one of the few cancers whereby incidence rates have increased in recent years. It occurs in all age groups, from children through to seniors. Most studies are focused on dissecting its genetic basis, since our current knowledge of the genetic background of the different forms of thyroid cancer is far from complete, which poses a challenge for diagnosis and prognosis of the disease. In this review, we describe prevailing advances and update our understanding of the molecular genetics of thyroid cancer, focusing on the main genes related with the pathology, including the different noncoding RNAs associated with the disease.

124I Positron Emission Tomography/Computed Tomography Versus Conventional Radioiodine Imaging in Differentiated Thyroid Cancer: A Review

Background: Studies report a wide spectrum of ¹²⁴I positron emission tomography (PET)/computed tomography (CT) sensitivity and specificity in the detection of differentiated thyroid cancer (DTC) lesions. This study reviews the lesion detection rate of pretherapy ¹²⁴I PET/CT in different patient populations and further analyzes the factors necessary for a better detection on ¹²⁴I PET/CT. Methods: A literature search was performed using multiple different databases (MEDLINE, EMBASE, Northern Lights, and handsearching) covering 1996 to April 2018. Two reviewers reviewed and extracted study data for ¹²⁴I, ¹²³I, and ¹³¹I scans in DTC. Results: This review includes 4 retrospective and 10 prospective studies in which 495 DTC patients underwent ¹²⁴I and ¹³¹I imaging; no studies made comparisons with ¹²³I. In the reports that compared ¹²⁴I PET/CT with diagnostic ¹³¹I scans, there were a total of 72 patients in whom 120 lesions were detected on ¹²⁴I imaging, whereas only 52 were detected on diagnostic ¹³¹I scans. In publications that compared ¹²⁴I with post-therapy ¹³¹I scans in 266 patients, 410 lesions were detected with ¹²⁴I PET, whereas 390 were detected on post-therapy ¹³¹I scans. Based on ¹²⁴I PET/CT in six studies, TNM staging was revised in 15-21% of patients, and disease management was altered in 5-29% of patients. Conclusions:¹²⁴I PET/CT is able to identify a greater number of foci compared with diagnostic ¹³¹I scans. ¹²⁴I PET may have better detection compared with post-therapy ¹³¹I scans in patients who are ¹³¹I therapy naive, have less aggressive pathology, or do not have disseminated lung metastases. Additional metastatic lesion detection by ¹²⁴I PET may have a significant clinical impact in the management of patients before ¹³¹I therapy in some patients.

Mitogen-Activated Protein Kinase Pathway Inhibition for Redifferentiation of Radioiodine Refractory Differentiated Thyroid Cancer: An Evolving Protocol

Background: Some patients with metastatic differentiated thyroid cancer (DTC) lack iodine avidity and are therefore unsuitable for radioactive iodine (RAI) therapy. Limited experience suggests that single-agent selective mitogen-activated protein kinase (MAPK) pathway inhibitors can restore expression of the sodium-iodide symporter rendering RAI refractory (RAIR) DTC patients amenable to RAI therapy. The aim of this study was to assess the feasibility of mutation-guided MAPK-pathway blockade combined with thyroid hormone withdrawal (THW) for redifferentiation. Methods: This is a retrospective review of metastatic RAIR DTC and driver mutation in MAPK pathway, treated on a redifferentiation protocol. All patients had metastatic disease that had never been RAI-avid and/or imaging and biochemical progression despite treatment with RAI within the past 12 months. Patients with tumors harboring an NRAS mutation were treated with an MEK inhibitor (trametinib), and tumors with a BRAF^V600E mutation with combined BRAF and MEK inhibition (dabrafenib and trametinib; or vemurafenib and cobimetinib) for four weeks. Thyrotropin stimulation was performed by THW for four weeks. Restoration of RAI uptake was determined by ¹²⁴I positron emission tomography/computed tomography imaging. The response was assessed at least three months post-RAI. Results: From 2015 to 2017, six patients (age 45-70, four females) received redifferentiation therapy. Three patients had an NRAS mutation; two with follicular thyroid carcinoma (FTC) and one with a poorly differentiated thyroid carcinoma (PDTC); and three patients had a BRAF^V600E mutation and papillary thyroid carcinoma (PTC). One NRAS and all BRAF^V600E mutation cases demonstrated restoration of RAI uptake and proceeded to RAI therapy with a median follow-up of 16.6 months (range 13.5-42.3 months). The patient with an NRAS mutation and two of three patients with a BRAF^V600E demonstrated partial imaging response beyond a three-month follow-up. Grade 3 adverse events (acneiform rash) were observed in two patients with NRAS mutations. Conclusions: Mutation-guided MAPK pathway inhibition with MEK inhibitor or a combination of BRAF inhibitor and MEK inhibitor under concurrent THW is a feasible and a promising strategy to redifferentiate RAIR DTC, thereby rendering them suitable for RAI therapy with satisfactory retention following treatment.

Dual inhibition of BRAF and MEK increases expression of sodium iodide symporter in patient-derived papillary thyroid cancer cells in vitro

BACKGROUND

The majority of papillary thyroid cancers are driven by acquired mutations typically in the BRAF or RAS genes that aberrantly activate the mitogen-activated protein kinase pathway. This process leads to malignant transformation, dedifferentiation, and a decrease in the expression of the sodium-iodide symporter (NIS; SLC5A5), which results in resistance to radioactive iodine therapy. We sought to determine whether inhibition of aberrant mitogen-activated protein kinase-signaling can restore NIS expression.

METHODS

We prospectively developed cultures of papillary thyroid cancers derived from operative specimens and applied drug treatments for 24 hours. Samples were genotyped to identify BRAF and RAS mutations. We performed quantitative PCR to measure NIS expression after treatment.

RESULTS

We evaluated 24 patient papillary thyroid cancer specimens; BRAF^V600E mutations were identified in 18 out of 24 (75.0%); 1 patient tumor had an HRAS mutation, and the remaining 5 were BRAF and RAS wildtype. Dual treatment with dabrafenib and trametinib increased NIS expression (mean fold change 4.01 ± 2.04, P < .001), and single treatment with dabrafenib had no effect (mean fold change 0.98 ± 0.42, P = .84). Tumor samples that had above-median NIS expression increases came from younger patients (39 vs 63 years, P < .05).

CONCLUSION

Dual treatment with BRAF and MEK inhibitors upregulated NIS expression, suggesting that this treatment regimen may increase tumor iodine uptake. The effect was greatest in tumor cells from younger patients.

Differentiated Thyroid Cancer in the Pediatric/Adolescent Population: Evolution of Treatment

Differentiated thyroid cancer (DTC) is the most common cancer in adolescents and young adults. In 2015, the American Thyroid Association published guidelines for management of pediatric DTC. We report our institutional experience and highlight changing practices and new opportunities. A retrospective analysis of all patients diagnosed with DTC from 2001 to 2016 was performed. Among 59 eligible patients, 31 (53%), 15 (25%), and 13 (22%) had low-risk, intermediate-risk, and high-risk disease, respectively. Half (15/31) of low-risk and all intermediate-risk/high-risk patients received radioactive iodine (I-131) ablation. For low-risk patients, average I-131 dose decreased from 80 to 42.05 mCi, and the percentage of patients who received I-131 decreased over time. Eleven of 16 patients with tumor genomic data were found to have somatic targetable (n=6) or germline (n=5) mutations. Persistent/recurrent disease was only present in high-risk (n=8) and intermediate-risk (n=1) patients. Two patients with iodine-refractory disease received trametinib to enhance radioiodine uptake. All patients were alive at follow-up (median, 5 y; range, 1 to 15 y). Coincident with the recent American Thyroid Association guidelines, the use of I-131 in low-risk patients has decreased over time in our practice. Tumor sequencing and cancer genetic evaluation may help redefine opportunities for treatment of high-risk patients and family counseling.

Dimerization of the Sodium/Iodide Symporter

Background: The ability of thyroid follicular epithelial cells to accumulate iodide via the sodium/iodide symporter (NIS) is exploited to successfully treat most thyroid cancers, although a subset of patients lose functional NIS activity and become unresponsive to radioiodide therapy, with poor clinical outcome. Our knowledge of NIS regulation remains limited, however. While numerous membrane proteins are functionally regulated via dimerization, there is little definitive evidence of NIS dimerization, and whether this might impact upon radioiodide uptake and treatment success is entirely unknown. We hypothesized that NIS dimerizes and that dimerization is a prerequisite for iodide uptake. Methods: Coimmunoprecipitation, proximity ligation, and Förster resonance energy transfer (FRET) assays were used to assess NIS:NIS interaction. To identify residues involved in dimerization, a homology model of NIS structure was built based on the crystal structure of the dimeric bacterial protein vSGLT. Results: Abundant cellular NIS dimerization was confirmed in vitro via three discrete methodologies. FRET and proximity ligation assays demonstrated that while NIS can exist as a dimer at the plasma membrane (PM), it is also apparent in other cellular compartments. Homology modeling revealed one key potential site of dimeric interaction, with six residues <3Å apart. In particular, NIS residues Y242, T243, and Q471 were identified as critical to dimerization. Individual mutation of residues Y242 and T243 rendered NIS nonfunctional, while abrogation of Q471 did not impact radioiodide uptake. FRET data show that the putative dimerization interface can tolerate the loss of one, but not two, of these three clustered residues. Conclusions: We show for the first time that NIS dimerizes in vitro, and we identify the key residues via which this happens. We hypothesize that dimerization of NIS is critical to its trafficking to the PM and may therefore represent a new mechanism that would need to be considered in overcoming therapeutic failure in patients with thyroid cancer.

Molecular Alterations in Thyroid Carcinoma

Thyroid carcinoma is the most common cancer in the endocrine system. Recent advances, using next-generation sequencing, have shed light on the molecular pathogenesis of thyroid cancer. Constitutional activation of the mitogen-activated protein kinase pathway through RAS mutation, BRAF mutation, and/or fusions involving receptor tyrosine kinase (eg, (REarranged during Transfection) RET-PTC) plays a central role in tumorigenesis and opens doors to promising tyrosine kinase inhibitor therapy. Several molecular signatures, such as TERT promoter mutation and TP53 mutation, are associated with tumor progression. This article provides a concise and updated summary of the main genetic alterations in thyroid carcinoma.

Radioiodine-Refractory Thyroid Cancer: Molecular Basis of Redifferentiation Therapies, Management, and Novel Therapies

Recurrent, metastatic disease represents the most frequent cause of death for patients with thyroid cancer, and radioactive iodine (RAI) remains a mainstay of therapy for these patients. Unfortunately, many thyroid cancer patients have tumors that no longer trap iodine, and hence are refractory to RAI, heralding a poor prognosis. RAI-refractory (RAI-R) cancer cells result from the loss of thyroid differentiation features, such as iodide uptake and organification. This loss of differentiation features correlates with the degree of mitogen-activated protein kinase (MAPK) activation, which is higher in tumors with BRAF (B-Raf proto-oncogene) mutations than in those with RTK (receptor tyrosine kinase) or RAS (rat sarcoma) mutations. Hence, inhibition of the mitogen-activated protein kinase kinase-1 and -2 (MEK-1 and -2) downstream of RAF (rapidly accelerated fibrosarcoma) could sensitize RAI refractivity in thyroid cancer. However, a significant hurdle is the development of secondary tumor resistance (escape mechanisms) to these drugs through upregulation of tyrosine kinase receptors or another alternative signaling pathway. The sodium iodide symporter (NIS) is a plasma membrane glycoprotein, a member of solute carrier family 5A (SLC5A5), located on the basolateral surfaces of the thyroid follicular epithelial cells, which mediates active iodide transport into thyroid follicular cells. The mechanisms responsible for NIS loss of function in RAI-R thyroid cancer remains unclear. In a study of patients with recurrent thyroid cancer, expression levels of specific ribosomal machinery-namely PIGU (phosphatidylinositol glycan anchor biosynthesis class U), a subunit of the GPI (glycosylphosphatidylinositol transamidase complex-correlated with RAI avidity in radioiodine scanning, NIS levels, and biochemical response to RAI treatment. Here, we review the proposed mechanisms for RAI refractivity and the management of RAI-refractive metastatic, recurrent thyroid cancer. We also describe novel targeted systemic agents that are in use or under investigation for RAI-refractory disease, their mechanisms of action, and their adverse events.

Personalized treatment options for thyroid cancer: current perspectives

Thyroid cancer is one of the most common endocrine malignancies, with increasing incidence all over the world. In spite of good prognosis for differentiated thyroid carcinoma, for an unknown reason, about 5–10% of the patients, the cancer will show aggressive behavior, develop metastasis, and be refractory to treatment strategies like radioactive iodine. Regarding the genetic information, each thyroid cancer patient can be considered as an individual unique one, with unique genetic information. Contrary to standard chemotherapy drugs, target therapy components aim at one or more definite molecular pathway on cancer cells, so their selection is underlying patient’s genetic information. Nowadays, several mutations and rearrangements including BRAF, VEGF receptors, RET, and RET/PTC, KDR, KIT, PDGFRA, CD274, and JAK2 are taken into account for the therapeutic components like larotrectinib (TRK inhibitor), vemurafenib, sunitinib, sorafenib, selumetinib, and axitinib. With the new concept of personalized treatment of thyroid cancer diagnoses, planning treatment, finding out how well treatment will work, and estimating a prognosis has changed for the better over the last decade.

Molecular Alterations in Thyroid Cancer: From Bench to Clinical Practice

Thyroid cancer comprises different clinical and histological entities. Whereas differentiated (DTCs) malignancies are sensitive to radioiodine therapy, anaplastic (ATCs) and medullary (MTCs) tumors do not uptake radioactive iodine and display aggressive features associated with a poor prognosis. Moreover, in a majority of DTCs, disease evolution leads to the progressive loss of iodine sensitivity. Hence, iodine-refractory DTCs, along with ATCs and MTCs, require alternative treatments reflective of their different tumor biology. In the last decade, the molecular mechanisms promoting thyroid cancer development and progression have been extensively studied. This has led to a better understanding of the genomic landscape, displayed by thyroid malignancies, and to the identification of novel therapeutic targets. Indeed, several pharmacological compounds have been developed for iodine-refractory tumors, with four multi-target tyrosine kinase inhibitors already available for DTCs (sorafenib and lenvatinib) and MTCs (cabozantib and vandetanib), and a plethora of drugs currently being evaluated in clinical trials. In this review, we will describe the genomic alterations and biological processes intertwined with thyroid cancer development, also providing a thorough overview of targeted drugs already tested or under investigation for these tumors. Furthermore, given the existing preclinical evidence, we will briefly discuss the potential role of immunotherapy as an additional therapeutic strategy for the treatment of thyroid cancer.

The cholesterol-derived metabolite dendrogenin A functionally reprograms breast adenocarcinoma and undifferentiated thyroid cancer cells

Dendrogenin A (DDA) is a tumor suppressor mammalian cholesterol-derived metabolite and a new class of ligand of the Liver X receptor (LXR), which displays tumor cell differentiation. In human MCF7 breast adenocarcinoma cells, DDA-induced cell differentiation was associated with an increased accumulation of neutral lipids and proteins found in milk indicating that DDA re-activates some functions of lactating cells. Active iodide transport occurs in the normal lactating mammary cells through the sodium/iodide symporter (NIS) and iodide (I) is secreted into milk to be used by the nursing newborn for thyroid hormones biosynthesis. In the present study, we assessed whether DDA may induce other characteristic of lactating cells such as NIS expression and iodine uptake in MCF7 breast cancer cells and extended this study to the papillary B-CPAP and undifferentiated anaplastic 8505c thyroid cancer cells. Moreover, we evaluated DDA impact on the expression of thyroid specific proteins involved in thyroid hormone biogenesis. We report here that DDA induces NIS expression in MCF7 cells and significantly increases the uptake of 131-I by acting through the LXR. In addition, DDA induces phenotypic, molecular and functional characteristics of redifferentiation in the two human thyroid carcinoma cell lines and the uptake of 131-I in the undifferentiated 8505c cells was associated with a strong expression of all the specific proteins involved in thyroid hormone biosynthesis, TSH receptor, thyroperoxidase and thyroglobulin. 131-I incorporation in the 8505c cells was stimulated by DDA as well as by the synthetic LXR ligand, GW3965. Together these data show that the re-differentiation of breast and thyroid cancer cells by DDA, is associated with the recovery of functional NIS expression and involves an LXR-dependent mechanism. These results open new avenues of research for the diagnosis of thyroid cancers as well as the development of new therapeutic approaches for radioiodine refractory thyroid cancers.

Radioactive Iodine-Refractory Differentiated Thyroid Cancer and Redifferentiation Therapy

The retained functionality of the sodium iodide symporter (NIS) expressed in differentiated thyroid cancer (DTC) cells allows the further utilization of post-surgical radioactive iodine (RAI) therapy, which is an effective treatment for reducing the risk of recurrence, and even the mortality, of DTC. Whereas, the dedifferentiation of DTC could influence the expression of functional NIS, thereby reducing the efficacy of RAI therapy in advanced DTC. Genetic alternations (such as BRAF and the rearranged during transfection [RET]/papillary thyroid cancer [PTC] rearrangement) have been widely reported to be prominently responsible for the onset, progression, and dedifferentiation of PTC, mainly through activating the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) signaling cascades. These genetic alternations have been suggested to associate with the reduced expression of iodide-handling genes in thyroid cancer, especially the NIS gene, disabling iodine uptake and causing resistance to RAI therapy. Recently, novel and promising approaches aiming at various targets have been attempted to restore the expression of these iodine-metabolizing genes and enhance iodine uptake through in vitro studies and studies of RAI-refractory (RAIR)-DTC patients. In this review, we discuss the regulation of NIS, known mechanisms of dedifferentiation including the MAPK and PI3K pathways, and the current status of redifferentiation therapy for RAIR-DTC patients.

Thyroid Cancer Bone Metastasis: Survival and Genomic Characteristics of a Large Tertiary Care Cohort

Bone metastasis (BM) in differentiated thyroid cancer (DTC) is the second most common site of metastasis after lung. Bone metastases are associated with worse prognosis in DTC. In this study, we examined risk factors for overall survival in patients with BM and for the first time explore the pattern of genomic alterations in DTC BM.

PATIENTS AND METHODS

A Health Insurance Portability and Accountability Act (HIPAA) compliant, institutional review board-approved retrospective evaluation of the medical record was performed for all patients treated at a single institution for thyroid cancer over a 16-year period. Seventy-four patients met inclusion criteria. Multiple prognostic factors including age, sex, genes, radioactive iodine, and radiation or kinase inhibitor therapies were analyzed. Univariate and multivariate analyses were performed.

RESULTS

Treatment with external beam radiation was found to significantly increase survival (P = 0.03). The 5-year survival rate was 59% and median survival was 92 months. Patients who developed bone metastasis earlier tend to live longer (P = 0.06). The presence of TERT and BRAF mutations did not significantly worsen the prognosis (P = 0.10).

CONCLUSION

Patients with DTC can benefit from early treatment with external beam radiation therapy, especially those who develop bone metastasis within 3 years of primary TC diagnosis. Kinase inhibitor treatment tended to prolong survival but not in a statistically significant manner. Sex, age, and TERT or BRAF genetic mutations did not significantly affect the prognosis.

Integrating molecular nuclear imaging in clinical research to improve anticancer therapy

Effective patient selection before or early during treatment is important to increasing the therapeutic benefits of anticancer treatments. This selection process is often predicated on biomarkers, predominantly biospecimen biomarkers derived from blood or tumour tissue; however, such biomarkers provide limited information about the true extent of disease or about the characteristics of different, potentially heterogeneous tumours present in an individual patient. Molecular imaging can also produce quantitative outputs; such imaging biomarkers can help to fill these knowledge gaps by providing complementary information on tumour characteristics, including heterogeneity and the microenvironment, as well as on pharmacokinetic parameters, drug-target engagement and responses to treatment. This integrative approach could therefore streamline biomarker and drug development, although a range of issues need to be overcome in order to enable a broader use of molecular imaging in clinical trials. In this Perspective article, we outline the multistage process of developing novel molecular imaging biomarkers. We discuss the challenges that have restricted the use of molecular imaging in clinical oncology research to date and outline future opportunities in this area.

Activation of the IGF Axis in Thyroid Cancer: Implications for Tumorigenesis and Treatment

The Insulin-like growth factor (IGF) axis is one of the best-established drivers of thyroid transformation, as thyroid cancer cells overexpress both IGF ligands and their receptors. Thyroid neoplasms encompass distinct clinical and biological entities as differentiated thyroid carcinomas (DTC)-comprising papillary (PTC) and follicular (FTC) tumors-respond to radioiodine therapy, while undifferentiated tumors-including poorly-differentiated (PDTC) or anaplastic thyroid carcinomas (ATCs)-are refractory to radioactive iodine and exhibit limited responses to chemotherapy. Thus, safe and effective treatments for the latter aggressive thyroid tumors are urgently needed. Despite a strong preclinical rationale for targeting the IGF axis in thyroid cancer, the results of the available clinical studies have been disappointing, possibly because of the crosstalk between IGF signaling and other pathways that may result in resistance to targeted agents aimed against individual components of these complex signaling networks. Based on these observations, the combinations between IGF-signaling inhibitors and other anti-tumor drugs, such as DNA damaging agents or kinase inhibitors, may represent a promising therapeutic strategy for undifferentiated thyroid carcinomas. In this review, we discuss the role of the IGF axis in thyroid tumorigenesis and also provide an update on the current knowledge of IGF-targeted combination therapies for thyroid cancer.

Radioiodine Imaging for Differentiated Thyroid Cancer: Not All Radioiodine Images Are Performed Equally

Background: Radioiodine scanning may help risk stratify patients with differentiated thyroid carcinoma (DTC) during initial and subsequent restaging. To maximize the information obtained from radioiodine scanning, image quality and interpretation should be optimized. However, not all radioiodine scans are performed equally. This illustrated article reviews seven techniques that may significantly improve the information obtained from a radioiodine scan in patients with DTC, which in turn may alter management such as showing regional or distant metastases that were otherwise unknown and/or help classify whether a metastasis is radioiodine avid. Summary: The first of the techniques is spot imaging of anatomical areas of interest using a gamma camera with a parallel-hole collimator. Spot images typically provide superior spatial resolution and enhanced lesion detection compared with whole-body scans using the same equipment. The second technique is spot imaging of the thyroid bed and neck with a pin-hole collimator, further improving spatial resolution. Two other techniques, delayed image acquisition and longer acquisition time, may clarify the nature of indeterminate foci of uptake or areas with negative initial findings. Delayed image acquisition may increase tumor-to-background ratio and thus improves lesion detectability. Longer acquisition times also increase contrast resolution between lesions and background activity, again increasing the detectability of malignant lesions. The fifth technique, adjustment of image brightness/contrast on film or on the computer screen, may reveal previously unobserved subtle differences in counts. The sixth technique, focus-specific history, comprises additional patient information that is specific to a focus of radioiodine uptake and elicited by the nuclear medicine physician or technologist. The goal is to help determine if the focus represents a metastasis or an artifact, which in turn decreases false positives and increases specificity. The seventh technique, single-photon emission computed tomography/computed tomography, improves contrast resolution and helps localize foci of uptake to anatomical structures. Conclusions: Technique is important to maximize information obtained from radioiodine scans in patients with DTC. With the greater usage and understanding of these seven techniques, physicians will significantly improve the information obtained from a radioiodine scan in patients with DTC, which in turn may alter management and potentially outcomes.

V211D Mutation in MEK1 Causes Resistance to MEK Inhibitors in Colon Cancer

We report the emergence of the novel MEK1 ^V211D gatekeeper mutation in a patient with BRAF ^K601E colon cancer treated with the allosteric MEK inhibitor binimetinib and the anti-EGFR antibody panitumumab. The MEK1 ^V211D mutation concurrently occurs in the same cell with BRAF ^K601E and leads to RAF-independent activity but remains regulated by RAF. The V211D mutation causes resistance to binimetinib by both increasing the catalytic activity of MEK1 and reducing its affinity for the drug. Moreover, the mutant exhibits reduced sensitivity to all the allosteric MEK inhibitors tested. Thus, this mutation serves as a general resistance mutation for current MEK inhibitors; however, it is sensitive to a newly reported ATP-competitive MEK inhibitor, which therefore could be used to overcome drug resistance. SIGNIFICANCE: We report a resistance mechanism to allosteric MEK inhibitors in the clinic. A MEK1 ^V211D mutation developed in a patient with BRAF ^K601E colon cancer on MEK and EGFR inhibitors. This mutant increases the catalytic activity of MEK1 and reduces its affinity for binimetinib, but remains sensitive to ATP-competitive MEK inhibitors.This article is highlighted in the In This Issue feature, p. 1143.

Investigating the potential clinical benefit of Selumetinib in resensitising advanced iodine refractory differentiated thyroid cancer to radioiodine therapy (SEL-I-METRY): protocol for a multicentre UK single arm phase II trial

BACKGROUND

Thyroid cancer is the most common endocrine malignancy. Some advanced disease is, or becomes, resistant to radioactive iodine therapy (refractory disease); this holds poor prognosis of 10% 10-year overall survival. Whilst Sorafenib and Lenvatinib are now licenced for the treatment of progressive iodine refractory thyroid cancer, these treatments require continuing treatment and can be associated with significant toxicity. Evidence from a pilot study has demonstrated feasibility of Selumetinib to allow the reintroduction of I-131 therapy; this larger, multicentre study is required to demonstrate the broader clinical impact of this approach before progression to a confirmatory trial.

METHODS

SEL-I-METRY is a UK, single-arm, multi-centre, two-stage phase II trial. Participants with locally advanced or metastatic differentiated thyroid cancer with at least one measureable lesion and iodine refractory disease will be recruited from eight NHS Hospitals and treated with four-weeks of oral Selumetinib and assessed for sufficient I-123 uptake (defined as any uptake in a lesion with no previous uptake or 30% or greater increase in uptake). Those with sufficient uptake will be treated with I-131 and followed for clinical outcomes. Radiation absorbed doses will be predicted from I-123 SPECT/CT and verified from scans following the therapy. Sixty patients will be recruited to assess the primary objective of whether the treatment schedule leads to increased progression-free survival compared to historical control data.

DISCUSSION

The SEL-I-METRY trial will investigate the effect of Selumetinib followed by I-131 therapy on progression-free survival in radioiodine refractory patients with differentiated thyroid cancer showing increased radioiodine uptake following initial treatment with Selumetinib. In addition, information on toxicity and dosimetry will be collected. This study presents an unprecedented opportunity to investigate the role of lesional dosimetry in molecular radiotherapy, leading to greater personalisation of therapy. To date this has been a neglected area of research. The findings of this trial will be useful to healthcare professionals and patients alike to determine whether further study of this agent is warranted. It is hoped that the development of the infrastructure to deliver a multicentre trial involving molecular radiotherapy dosimetry will lead to further trials in this field.

TRIAL REGISTRATION

SEL-I-METRY is registered under ISRCTN17468602 , 02/12/2015.

A Phase I Trial of the VEGF Receptor Tyrosine Kinase Inhibitor Pazopanib in Combination with the MEK Inhibitor Trametinib in Advanced Solid Tumors and Differentiated Thyroid Cancers

PURPOSE

Differentiated thyroid cancer (DTC) responds to VEGF receptor inhibitors. VEGF signals through RAS/RAF/MEK signaling. We evaluated the safety and efficacy of the VEGF receptor inhibitor pazopanib and MEK inhibitor trametinib in advanced solid tumors and DTC.

PATIENTS AND METHODS

Patients with advanced solid tumors were enrolled in a phase I, multicenter trial with a DTC expansion cohort. Patients received pazopanib 400-800 mg and trametinib 1-2 mg daily. Efficacy in the expansion cohort was assessed with objective response (OR) at 6 months of treatment.

RESULTS

Twenty-six patients were enrolled in five dose levels. MTD was not reached; the recommended phase II dose was pazopanib 800 mg orally and trametinib 2 mg orally every day. There was one dose-limiting toxicity on dose level 1 with grade 3 fatigue and muscle weakness. Common grade 3 adverse events were elevated transaminases (19%), diarrhea (15%), hypertension (12%), and fatigue (8%). Thirteen patients were enrolled in the DTC cohort; OR was 33% (95% confidence interval, 9.9, 65.1%) and median progression-free survival was 10.7 months. The cohort was terminated after planned interim analysis suggested insufficiently increased activity against the historical control of pazopanib alone. Reduction in tumor diameter negatively correlated with p-ERK change in tumor (Spearman ρ = -0.71; P = 0.05). NRAS mutation was associated with response (Fisher exact P = 0.008).

CONCLUSIONS

Pazopanib + trametinib was tolerable at full single-agent doses with clinical activity in DTC but did not achieve the prespecified response rate target.

AXL Is a Novel Predictive Factor and Therapeutic Target for Radioactive Iodine Refractory Thyroid Cancer

Papillary thyroid carcinomas (PTCs) have an excellent prognosis, but a fraction of them show aggressive behavior, becoming radioiodine (RAI)-resistant and/or metastatic. AXL (Anexelekto) is a tyrosine kinase receptor regulating viability, invasiveness and chemoresistance in various human cancers, including PTCs. Here, we analyze the role of AXL in PTC prognosis and as a marker of RAI refractoriness. Immunohistochemistry was used to assess AXL positivity in a cohort of human PTC samples. Normal and cancerous thyroid cell lines were used in vitro for signaling, survival and RAI uptake evaluations. 38.2% of human PTCs displayed high expression of AXL that positively correlated with RAI-refractoriness and disease persistence or recurrence, especially when combined with v-raf murine sarcoma viral oncogene homolog B(BRAF) V600E mutation. In human PTC samples, AXL expression correlated with V-akt murine thymoma viral oncogene homolog 1 (AKT1) and p65 nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) activation levels. Consistently, AXL stimulation with its ligand growth arrest-specific gene 6 (GAS6) increased AKT1- and p65 NF-kB-phosphorylation and promoted survival of thyroid cancer cell lines in culture. Enforced expression or activation of AXL in normal rat thyroid cells significantly reduced the expression of the sodium/iodide symporter (NIS) and the radioiodine uptake. These data indicate that AXL expression levels could be used as predictor of RAI refractoriness and as a possible novel therapeutic target of RAI resistant PTCs.

Still Perfecting Radioiodine in Thyroid Cancer, After All These Years

Dunn et al. report on vemurafenib redifferentiation in BRAFV660E DTC. Tumor biopsies showed pharmacologic reprogramming. Decades after RAI was brought into the clinic, we are still perfecting its use.

Redifferentiation of a BRAFK601E-Mutated Poorly Differentiated Thyroid Cancer Patient with Dabrafenib and Trametinib Treatment

A 59-year-old woman with locally invasive poorly differentiated thyroid cancer with synchronous lung, mediastinal, and bone metastases and a somatic BRAF^K601E mutation with contraindication for antiangiogenic drugs was treated with dabrafenib and trametinib. During treatment, serum levels of thyroglobulin increased as early as day 7 up to 10-fold over baseline at week 4. Concurrently, clinical hyperthyroidism occurred, with free triiodothyronine and free thyroxine levels increasing to 6.6 and 4.4 times their upper reference limit. Fludeoxyglucose positron emission tomography/computed tomography at one and two months after treatment initiation showed a PERCIST metabolic response with a 82% decrease in fludeoxyglucose uptake, whereas disease remained morphologically stable according to RECIST criteria. A diagnostic radioactive iodine whole-body scan performed when the patient was thyrotoxic with an undetectable serum thyrotropin level, in the absence of any exogenous thyrotropin stimulation, showed high radioactive iodine uptake in the lung, mediastinum, and skull metastases. A biopsy performed two months after treatment initiation showed a more differentiated growth pattern and a decrease in the mitotic activity compared to baseline. An increase of thyroglobulin and thyroid peroxidase was observed at both the protein and mRNA levels. Sodium-iodide symporter mRNA expression increased by >750 times over its initial level, and sodium-iodide symporter protein expression became detectable under treatment. A decrease in general status due to thyrotoxicosis led to treatment discontinuation. Thyrotoxicosis resolved rapidly and radioactive iodine uptake decreased by >90%. This clinical case shows that redifferentiation itself is not necessarily associated with an antitumor effect.