Larotrectinib-Enhanced Radioactive Iodine Uptake in Advanced Thyroid Cancer

An update on redifferentiation strategies for radioactive iodine-refractory differentiated thyroid carcinoma

PURPOSE

Although most patients with differentiated thyroid carcinoma (DTC) have an excellent prognosis, a subset will experience radioactive iodine refractory (RAI-R) disease, associated with recurrence, distant metastases and worse prognosis. In recent years, redifferentiation has emerged as an attractive approach for patients with RAI-R DTC, a strategy to induce iodine uptake in RAI-R DTC tumor cells and ultimately prolong time to initiation of systemic therapy.

METHODS

An overview and critical appraisal of the existing literature on redifferentiation will be presented in this review under the lens of the genotype-specific targeted therapy administered with redifferentiation intent.

RESULTS/CONCLUSIONS

Due to the significant heterogeneity across studies, it will be key to harmonize research methodology and support future larger, multicenter prospective trials in order to identify the most suitable candidates for this therapeutic strategy.

Recent advances in the use of tyrosine kinase inhibitors against thyroid cancer

INTRODUCTION

Oncogenic tyrosine kinases (TK) are enzymes that play a key role in cell growth and proliferation and their mutations can lead to uncontrolled cell growth and development of aggressive cancer. This knowledge has led to the development of new classes of drugs, Tyrosine kinase inhibitors (TKI). They target oncogenic kinases who are associated with advanced radioactive iodine (RAI) refractory TC, which is not able to uptake RAI anymore and/or still grows between consecutive treatments with Iodine 131 (I131).

AREAS COVERED

Since Lenvatinib and Sorafenib approval, several other molecular inhibitors have been studied and then introduced for the treatment of aggressive and refractory thyroid cancer (TC), and, although the development of adverse effects or tumor resistance mechanisms, more and more compounds are still under investigation. The literature search was executed in PubMed and ClinicalTrials.gov to identify relevant articles and clinical trials published until December 2023.

EXPERT OPINION

In the context of clinical trials, driven by the presence of specific molecular mutations or even in the absence of both conditions, systemic therapy TKIs are valuable weapons to be used in patients affected by aggressive forms of TC, waiting for further expansion of the treatment landscape with more efficacious and safer drugs.

An Era of Advances in Systemic Therapies for Advanced Thyroid Cancer

Thyroid carcinomas comprise distinct pathologic subtypes. However, advancements in characterizing the molecular tumorigenesis of thyroid cancers have changed the treatment paradigm in the past decade. Genetic profiling has become an integral component of personalizing cancer care. Oral kinase inhibitors are currently standard-of-care therapies for progressive, radioactive iodine (RAI)-refractory differentiated thyroid carcinomas (DTCs) and medullary thyroid carcinomas (MTCs). Sorafenib, lenvatinib, and cabozantinib are multikinase inhibitors approved for patients with metastatic RAI-refractory DTC, whereas vandetanib and cabozantinib are approved for patients with MTC. Management of thyroid carcinomas has evolved such that targeted therapies have become therapeutic options for patients with BRAF, RET, NTRK, ALK, and ROS1 alterations and even have reported efficacy in anaplastic thyroid carcinomas. In this article, we review the advances made over the years in the treatment of metastatic thyroid carcinoma and focus on the systemic therapies that have recently transformed the treatment landscape of advanced disease.

Anti-hyperuricemia bioactive peptides: a review on obtaining, activity, and mechanism of action

Hyperuricemia, a disorder of uric acid metabolism, serves as a significant risk factor for conditions such as hypertension, diabetes mellitus, renal failure, and various metabolic syndromes. The main contributors to hyperuricemia include overproduction of uric acid in the liver or impaired excretion in the kidneys. Despite traditional clinical drugs being employed for its treatment, significant health concerns persist. Recently, there has been growing interest in utilizing protein peptides sourced from diverse food origins to mitigate hyperuricemia. This article provides a comprehensive review of bioactive peptides with anti-hyperuricemia properties derived from animals, plants, and their products. We specifically outline the methods for preparing these peptides from food proteins and elucidate their efficacy and mechanisms in combating hyperuricemia, supported by in vitro and in vivo evidence. Uric acid-lowering peptides offer promising prospects due to their safer profile, enhanced efficacy, and improved bioavailability. Therefore, this review underscores significant advancements and contributions in identifying peptides capable of metabolizing purine and/or uric acid, thereby alleviating hyperuricemia. Moreover, it offers a theoretical foundation for the development of functional foods incorporating uric acid-lowering peptides.

Emerging therapeutic options for follicular-derived thyroid cancer in the era of immunotherapy

Although most follicular-derived thyroid cancers are well differentiated and have an overall excellent prognosis following treatment with surgery and radioiodine, management of advanced thyroid cancers, including iodine refractory disease and poorly differentiated/undifferentiated subtypes, is more challenging. Over the past decade, better understanding of the genetic drivers and immune milieu of advanced thyroid cancers has led to significant progress in the management of these patients. Numerous targeted kinase inhibitors are now approved by the U.S Food and Drug administration (FDA) for the treatment of advanced, radioiodine refractory differentiated thyroid cancers (DTC) as well as anaplastic thyroid cancer (ATC). Immunotherapy has also been thoroughly studied and has shown promise in selected cases. In this review, we summarize the progress in the understanding of the genetic landscape and the cellular and molecular basis of radioiodine refractory-DTC and ATC, as well as discuss the current treatment options and future therapeutic avenues.

Characterizing Genetic Alterations Related to Radioiodine Avidity in Metastatic Thyroid Cancer

CONTEXT

Patients with differentiated thyroid cancer (DTC) with distant metastasis (DM) are usually not recognized as radioactive iodine (RAI)-refractory DTC in a timely manner. The elucidation of genetic features related to RAI uptake patterns may shed light on the early recognition of RAI-refractory DTC.

OBJECTIVE

This work aimed to elucidate the underlying molecular features behind different RAI uptake patterns.

METHODS

A total of 214 patients with DM-DTC were retrospectively included in the analysis. RAI uptake patterns were defined as initially RAI refractory (I-RAIR) and initially RAI avid (I-RAIA) according to the first post-treatment scan, then I-RAIA was further divided into continually RAIA (C-RAIA), partly RAIR (P-RAIR), and gradually RAIR (G-RAIR) according to subsequent scans. The molecular subtype groups-BRAFV600E mutated, RAS mutated, fusions, and others-were classified according to main driver genes status.

RESULTS

BRAF, TERT promoter, and TP53 mutations are more frequently detected in the I-RAIR pattern while RET fusions and RAS mutations are more frequent in the I-RAIA pattern. A late-hit mutation including TERT, TP53, or PIK3CA is more common in I-RAIR than that in I-RAIA (50.0% vs 26.9%, P = .001), particularly for those with RAS mutations in the I-RAIR group, always accompanied by TERT promoter. Isolated RET fusions accounts for 10% of I-RAIR. When compared among driver gene groups, BRAFV600E-mutated tumors have a higher rate of the I-RAIR pattern (64.4%) than RAS-mutated (4.5%, P < .001) and fusion-positive (20.7%, P < .001) tumors. In I-RAIA subgroups, BRAFV600E-mutated tumors have lower prevalence of the C-RAIA pattern than those with RAS mutation or fusions.

CONCLUSION

Patients with the I-RAIR pattern predominantly featured mutations of the BRAF and/or TERT promoter, of which RAS mutations were usually accompanied by late-hit mutations, while fusions mostly occurred alone.

Summary and update on the management of differentiated thyroid cancer in 2023

The 6-fold increase in the incidence of differentiated thyroid cancer over the past 30 years in industrialized countries can be mainly attributed to improved detection. At the same time, in addition to the excellent prognosis for low-risk cancers, improved survival in metastatic forms has been also reported, likely due to the progress made recently in the treatment of aggressive forms, for which there is now an extensive therapeutic arsenal. Today, clinical management of differentiated thyroid cancer represents a paradigm of precision oncology, with personalized, risk-adapted therapeutic strategies. This has led to therapeutic de-escalation in those forms with a good prognosis, while targeted treatments play an increasingly important role in the management of radioiodine-refractory or advanced cancers. While endocrinologists will not always have the opportunity to prescribe these treatments, they will be called on to support and monitor patients during treatment. The aim of this article is to provide an overview of treatment options for differentiated thyroid cancer in 2023.

Will metformin use lead to a decreased risk of thyroid cancer? A systematic review and meta-analyses

BACKGROUND

It has been reported that metformin use may reduce the risk of thyroid cancer, but existing studies have generated inconsistent results. The purpose of this study was to investigate such association between metformin use and the risk of thyroid cancer.

METHODS

Studies of metformin use for the risk of thyroid cancer were searched in Web of Science, PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, China Biomedical Database, Wanfang Data, and Chinese Scientific Journals Database (VIP) from the establishment date to December 2022. Newcastle-Ottawa scale is adopted for assessing the methodological quality of included studies, and the inter-study heterogeneity was assessed by using the I-squared statistic. Combined odds ratios (ORs) with the corresponding 95% confidence intervals (CIs) were calculated through either fixed-effects or random-effects model according to the heterogeneity. Besides, subgroup analyses, sensitivity analyses and test for publication bias were conducted.

RESULTS

Five studies involving 1,713,528 participants were enrolled in the qualitative and quantitative synthesis. The result of the meta-analyses showed that metformin use was associated with a statistically significant lower risk of thyroid cancer (pooled OR = 0.68, 95% CI = 0.50-0.91, P = 0.011). Moreover, in the subgroup analysis, we found that the use of metformin may also aid in the prevention of thyroid cancer in Eastern population (pooled OR = 0.55, 95% CI = 0.35-0.88, P = 0.012) rather than Western population (pooled OR = 0.89, 95% CI = 0.52-1.54, P = 0.685). Sensitivity analysis suggested the results of this meta-analyses were relatively stable. No publication bias was detected.

CONCLUSION

Metformin use is beneficial for reducing the risk of thyroid cancer. For further investigation, more well-designed studies are still needed to elucidate the association between metformin use and the risk of thyroid cancer.

Children's Oncology Group's 2023 blueprint for research: Rare tumors

The Children's Oncology Group (COG) Rare Tumor Committee includes the Infrequent Tumor and Retinoblastoma subcommittees, encompassing a wide range of extracranial solid tumors that do not fall within another COG disease committee. Current therapeutic trial development focuses on nasopharyngeal carcinoma, adrenocortical carcinoma, pleuropulmonary blastoma, colorectal carcinoma, melanoma, and thyroid carcinoma. Given the rarity of these tumors, novel strategies and international collaborative efforts are necessary to advance research and improve outcomes.

NTRK Fusion in a Cohort of BRAF p. V600E Wild-Type Papillary Thyroid Carcinomas

Owing to the availability of a potent tropomyosin receptor kinase (TRK) inhibitor, it is necessary to develop an effective strategy to identify an enriched population of NTRK fusions in papillary thyroid carcinoma (PTC) in routine diagnostic practice. The reported prevalence of NTRK fusion in a large cohort of PTC is ∼3%. We performed an analysis to refine the characteristic histologic features of PTCs harboring NTRK fusions and further validate the diagnostic utility of pan-TRK immunohistochemistry as a screening tool. In this study, 450 PTCs known to harbor no BRAF p. V600E mutations were screened by pan-TRK immunohistochemistry, and the cases with TRK expression were confirmed by RNA-based next-generation sequencing assay. Eleven NTRK fusion cases were detected (2.4%), and all PTCs were classical subtypes. NTRK1 and NTRK3 were involved in the fusion with 9 different partner genes. Most cases showed similar characteristic histologic findings. Nodular permeative border, multinodular growth with a predominantly follicular pattern, extensive lymphatic invasion, and prominent internodular and intratumoral fibrosis were the characteristic histologic features of NTRK-rearranged PTCs. The ill-defined margins in the ultrasonography findings, which could not be clearly distinguished from the adjacent nontumorous thyroid tissue, were nodular permeative margins in histologic findings. Therefore, preoperative ultrasonographic findings in nodule margins were consistent with the final histologic findings. NTRK1/3 fusion in PTCs showed an overall sensitivity of 100% (95% CI, 71.51%-100%) and specificity of 100% (95% CI, 71.51%-100%) in the 22 cases examined, as confirmed with next-generation sequencing. Our study provides an integrative report of the preoperative ultrasonographic, histologic, immunohistochemical, and molecular features of NTRK-rearranged PTCs. Based on these findings, we propose an algorithmic approach for the stepwise assessment of NTRK fusions in PTCs.

Review article: new treatments for advanced differentiated thyroid cancers and potential mechanisms of drug resistance

The treatment of advanced, radioiodine refractory, differentiated thyroid cancers (RR-DTCs) has undergone major advancements in the last decade, causing a paradigm shift in the management and prognosis of these patients. Better understanding of the molecular drivers of tumorigenesis and access to next generation sequencing of tumors have led to the development and Food and Drug Administration (FDA)-approval of numerous targeted therapies for RR-DTCs, including antiangiogenic multikinase inhibitors, and more recently, fusion-specific kinase inhibitors such as RET inhibitors and NTRK inhibitors. BRAF + MEK inhibitors have also been approved for BRAF-mutated solid tumors and are routinely used in RR-DTCs in many centers. However, none of the currently available treatments are curative, and most patients will ultimately show progression. Current research efforts are therefore focused on identifying resistance mechanisms to tyrosine kinase inhibitors and ways to overcome them. Various novel treatment strategies are under investigation, including immunotherapy, redifferentiation therapy, and second-generation kinase inhibitors. In this review, we will discuss currently available drugs for advanced RR-DTCs, potential mechanisms of drug resistance and future therapeutic avenues.

Clinical role of 18F-FDG PET/CT for detection of radioactive iodine refractory differentiated thyroid cancer

In clinical settings, an estimated 10% differentiated thyroid cancer (DTC) cases become radioactive iodide refractory (RAIR), which lack a molecular marker and have fewer treatment selections. A higher uptake of 18F-fluorodeoxyglucose (18F-FDG) might indicate poor prognosis for DTC. This study aimed to evaluate the clinical value of 18F-FDG psitron emission tomography/computed tomography (PET/CT) for the early diagnosis of RAIR-DTC and high-risk DTC. A total of 68 DTC patients were enrolled and underwent 18F-FDG PET/CT for the detection of recurrence and/or metastasis. 18F-FDG uptake was evaluated in patients with different postoperative recurrence risks or TNM stages and compared between RAIR and non-RAIR-DTC based on its maximum standardized uptake value and tumor/liver (T/L) ratio. The final diagnosis was judged by histopathology and follow-up data. Of 68 DTC cases, 42 were RAIR and 24 non-RAIR, with 2 not determined. A total of 263 of 293 lesions detected on 18F-FDG PET/CT were confirmed to be locoregional or metastatic after follow-up. The T/L ratio was significantly higher for RAIR than for non-RAIR (median 5.18 vs 1.44; P < .01) and also significantly higher in postoperative patients at high-risk of recurrence than at low to medium risk (median 4.90 vs 2.16; P < .01). 18F-FDG PET/CT exhibited a sensitivity of 83.3% and specificity of 87.5% for identifying RAIR, with a cutoff T/L value of 2.98. 18F-FDG PET/CT has the potential to diagnose RAIR-DTC early and identify the high-risk DTC. The T/L ratio is a useful parameter for the detection of RAIR-DTC patients.

Inhibition of ALK-Signaling Overcomes STRN-ALK-Induced Downregulation of the Sodium Iodine Symporter and Restores Radioiodine Uptake in Thyroid Cells

Background: Radioiodine (RAI) is commonly used for thyroid cancer treatment, although its therapeutic benefits are restricted to iodine-avid tumors. The RAI-refractory disease develops with tumor dedifferentiation involving loss of sodium-iodine symporter (NIS). Thyroid cancers driven by ALK fusions are prone to dedifferentiation, and whether targeted ALK inhibition may enhance RAI uptake in these tumors remains unknown. The aim of this study was to determine the levels of NIS expression during the progression of ALK fusion-driven thyroid cancer, assess the effects of ALK activation on NIS-mediated RAI uptake, and test pharmacological options for its modulation. Methods: The expression of NIS at different stages of ALK-driven carcinogenesis was analyzed using a mouse model of STRN-ALK-driven thyroid cancer. For in vitro experiments, a system of doxycycline-inducible expression of STRN-ALK was generated using PCCL3 normal thyroid cells. The STRN-ALK-induced effects were evaluated with quantitative reverse transcription polymerase chain reaction, Western blot, immunofluorescence, RNA sequencing, and gene sets pathways analyses. RAI uptake was measured using 131I. Treatment experiments were done with FDA-approved ALK inhibitors (crizotinib and ceritinib), MEK inhibitor selumetinib, and JAK1/2 inhibitor ruxolitinib. Results: We found that Nis downregulation occurred early in ALK-driven thyroid carcinogenesis, even at the stage of well-differentiated cancer, with a complete loss in poorly differentiated thyroid carcinomas. Acute STRN-ALK expression in thyroid cells resulted in increased MAPK, JAK/STAT3, and PI3K/AKT/mTOR signaling outputs associated with significant ALK-dependent downregulation of the majority of thyroid differentiation and iodine metabolism/transport genes, including Slc5a5 (Nis), Foxe1, Dio1, Duox1/2, Duoxa2, Glis3, Slc5a8, and Tg. Moreover, STRN-ALK expression in thyroid cells induced a significant loss of membranous NIS and a fourfold decrease of the NIS-mediated RAI uptake, which were reversed by ALK inhibitors crizotinib and ceritinib. In addition, a strong dose-dependent restoration of NIS with its membranous redistribution in STRN-ALK-expressing thyroid cells was observed after inhibition of MAPK signaling with selumetinib, which exhibited a cumulative effect with JAK1/2 inhibitor ruxolitinib. Conclusions: The findings of this preclinical study showed that ALK fusion-induced downregulation of NIS, the prerequisite of RAI refractoriness, could be reversed in thyroid cells by either direct inhibition of ALK or its downstream signaling pathways.

NTRK fusions in thyroid cancer: Pathology and clinical aspects

Thyroid cancer is the most common endocrine cancer. Neurotrophic tyrosine receptor kinase (NTRK) fusions are oncogenic drivers in multiple solid tumors, including thyroid cancer. NTRK fusion thyroid cancer has unique pathological features such as mixed structure, multiple nodes, lymph node metastasis, and a background of chronic lymphocytic thyroiditis. Currently, RNA-based next-generation sequencing is the gold standard for the detection of NTRK fusions. Tropomyosin receptor kinase inhibitors have shown promising efficacy in patients with NTRK fusion-positive thyroid cancer. Efforts to overcome acquired drug resistance are the focus of research concerning next-generation TRK inhibitors. However, there are no authoritative recommendations or standardized procedures for the diagnosis and treatment of NTRK fusions in thyroid cancer. This review discusses current research progress regarding NTRK fusion-positive thyroid cancer, summarizes the clinicopathological features of the disease, and outlines the current statuses of NTRK fusion detection and targeted therapeutic agents.

Radioiodine therapy in advanced differentiated thyroid cancer: Resistance and overcoming strategy

Thyroid cancer is the most prevalent endocrine tumor and its incidence is fast-growing worldwide in recent years. Differentiated thyroid cancer (DTC) is the most common pathological subtype which is typically curable with surgery and Radioactive iodine (RAI) therapy (approximately 85%). Radioactive iodine is the first-line treatment for patients with metastatic Papillary Thyroid Cancer (PTC). However, 60% of patients with aggressive metastasis DTC developed resistance to RAI treatment and had a poor overall prognosis. The molecular mechanisms of RAI resistance include gene mutation and fusion, failure to transport RAI into the DTC cells, and interference with the tumor microenvironment (TME). However, it is unclear whether the above are the main drivers of the inability of patients with DTC to benefit from iodine therapy. With the development of new biological technologies, strategies that bolster RAI function include TKI-targeted therapy, DTC cell redifferentiation, and improved drug delivery via extracellular vesicles (EVs) have emerged. Despite some promising data and early success, overall survival was not prolonged in the majority of patients, and the disease continued to progress. It is still necessary to understand the genetic landscape and signaling pathways leading to iodine resistance and enhance the effectiveness and safety of the RAI sensitization approach. This review will summarize the mechanisms of RAI resistance, predictive biomarkers of RAI resistance, and the current RAI sensitization strategies.

Redifferentiation Therapy-Returning to Our Roots in a Post-Kinase Inhibitor World

Radioactive iodine (RAI) treatment is an effective treatment for differentiated thyroid cancer (DTC); however, many patients are refractory. Using targeted drugs to reinduce RAI sensitivity ("redifferentiation therapy") has long been sought after as the holy grail in endocrine oncology. See related article by Weber et al., p. 4194.

The potential long-term comparative effectiveness of larotrectinib vs standard of care for treatment of metastatic TRK fusion thyroid cancer, colorectal cancer, and soft tissue sarcoma

BACKGROUND: Larotrectinib is approved for patients with metastatic TRK fusion cancers, including differentiated thyroid (DTC), colorectal cancer (CRC), and soft tissue sarcoma (STS). Given the basket clinical trial design of larotrectinib, direct comparisons against standard of care in each of the mentioned cancers have not been assessed. Also, owing to the limited duration of follow-up in clinical trials, long-term outcomes for treatments are generally not known or estimated. OBJECTIVE: To compare expected life-years (LYs) and quality-adjusted life-years (QALYs) for patients with metastatic DTC, CRC, and STS who are eligible to receive larotrectinib against patients with unknown NTRK gene fusion status receiving standard-of-care therapy. METHODS: We developed a partitioned survival model to estimate the long-term comparative effectiveness of larotrectinib and standard of care for 3 tumor types. Larotrectinib survival data, assessed by independent review committee, were derived from an updated July 2020 analysis of 19, 8, and 23 adult patients (aged ≥ 18 years) with metastatic TRK fusion DTC, CRC, and STS, respectively. The DTC survival data also included 2 patients aged less than 18 years for a total of 21 patients. Survival estimates for standard of care were derived from published clinical trials. Progressionfree and overall survival for all treatments were estimated using survival distributions (Exponential, Weibull, Log-logistic, and Lognormal) fit to the available data. The final exponential form was selected based on goodness-of-fit and clinical plausibility. QALYs were estimated by adjusting the time spent in the preprogression and postprogression health states by utility weights derived from publicly available literature. RESULTS: Patients receiving larotrectinib experienced more LYs and QALYs compared with those receiving standard-of-care treatments across all 3 assessed cancer types. In DTC, patients receiving larotrectinib had 7.15-8.26 additional LYs (5.87-6.12 QALYs); in CRC, patients receiving larotrectinib had 1.26-1.27 additional LYs (1.00 QALYs); and in STS, patients receiving larotrectinib had 5.56 additional LYs (1.99 QALYs). CONCLUSIONS: Compared with standard of care in metastatic TRK wild-type cancers, larotrectinib is estimated to result in improved LY and QALY outcomes based on parametric extrapolations of intrial survival data. Because patient-level data were unavailable for adjusted analyses, a cross-trial comparison was performed. Given the limitations of this analytic approach and the small sample size for larotrectinib in trials, future studies should reassess the comparative effectiveness of larotrectinib vs standard of care as treated patients accrue and long-term survival data mature. DISCLOSURES: K. Suh, J. Carlson, and S. Sullivan report consulting fees from Bayer US LLC. F. Xia and T. Williamson are employees of Bayer US LLC. This study was funded by Bayer US LLC. The sponsor had no role in the design of the study and did not have any role in the execution, analyses, interpretation of the data, or decision to submit results.

Functional imaging in thyroid cancer patients with metastases and therapeutic implications

Functional imaging plays a central role in the management of thyroid cancer patients. In patients with a differentiated thyroid cancer (DTC), radioactive iodine (RAI) is used mostly with a therapeutic intent, either post-operatively or as the first line systemic treatment in patients with known structural disease. A whole body scan is performed a few days after the RAI administration, and this procedure is very sensitive to detect all tumor foci with RAI uptake. PET/CT with ¹⁸F-FDG complements the use of RAI at the initial evaluation of patients with high-risk DTC, during follow-up in those with rising serum thyroglobulin levels over time, for the work-up of patients with documented structural disease and for assessing the efficacy of focal or systemic treatment modalities. ¹⁸F-FDG uptake is a prognostic indicator in all these clinical conditions. A dosimetric approach with ¹²⁴I PET/CT showed encouraging results. Several functional imaging modalities are currently available for medullary thyroid carcinoma (MTC) patients. ¹⁸F-FDG-PET/CT may be sensitive in MTC patients with high FDG uptake that signals aggressive disease. ¹⁸F-DOPA is the most sensitive imaging technique to visualize small tumor foci, and is also highly specific in patients with a known MTC, but should be complemented by a CT scan of the chest and by a MRI of the liver to detect small metastases.

Novel Therapeutics for Advanced Differentiated Thyroid Cancer

The current treatments for radioactive iodine (RAI) -refractory differentiated thyroid cancer (DTC) are evolving as cancer genomics are further understood. Multitargeted tyrosine kinase inhibitors are the first-line therapy for symptomatic or progressive disease; however, considerable adverse effects have spurred the development of targeted therapies for redifferentiation of iodine avidity and the treatment of RAI-refractory DTC. Next-generation sequencing allows for the use of tumor-targeted therapeutics, such as MEK1/2, BRAF, RET, and NTRK inhibitors. Immunotherapy is also under investigation as a therapeutic option for this disease.

Emerging drugs for the treatment of radioactive iodine refractory papillary thyroid cancer

INTRODUCTION

The most frequent radioactive (RAI) refractory thyroid cancers are papillary thyroid carcinoma, followed by poorly differentiated thyroid carcinoma. They are rare and lethal. In recent years, significant therapeutic progress has been achieved.

AREAS COVERED

This paper offers insights on refractoriness to RAI treatment and the optimization of treatment initiation and treatment choice. Clinical trials performed with anti-angiogenic kinase inhibitors and with targeted inhibitors in patients with BRAF, RAS mutation or RET, TRK or ALK fusion are discussed.

EXPERT OPINION

These treatments provide high response rates. Anti-angiogenic kinase inhibitors improve median progression-free-survival; however, their benefit in terms of overall survival has been shown in only few subsets of patients. Treatment sequencing is challenging; in the absence of targetable abnormality, lenvatinib should be used as first line treatment. Options for second line treatment include lenvatinib (if not given at first line), cabozantinib or the addition of an anti-checkpoint antibody. In patients with a targetable abnormality, specific inhibitors, might be used as first line treatment and lenvatinib as second line or vice-versa. Further studies are needed, based on documented genomic and immunologic characteristics of the tumor to assess the potential role of combination and redifferentiation therapy.

Redifferentiating Effect of Larotrectinib in NTRK-Rearranged Advanced Radioactive-Iodine Refractory Thyroid Cancer

Metastatic thyroid cancers may dedifferentiate and become radioactive-iodine (RAI) resistant. A redifferentiating effect can be observed with inhibitors of the mitogen-activated protein kinase pathway in thyroid cancers with point mutation in oncogenes. This effect allows RAI reuptake that may lead to a therapeutic effect different from the antitumoral effect of the inhibitor. The potential redifferentiating effect of inhibitors targeting oncogenic fusion-genes was suggested by one adult and one pediatric patient using larotrectinib in NTRK-rearranged tumors. We report on three consecutive adult patients with metastatic RAI-resistant NTRK-rearranged thyroid cancer who received larotrectinib for disease progression and for whom the redifferentiating effect was examined. Larotrectinib-induced RAI reuptake in all or part of the metastatic disease for two patients and no reuptake was noted for the other patient. We demonstrate that redifferentiation of NTRK-rearranged RAI-resistant thyroid cancer with larotrectinib may exist but does not occur in all patients.

Fusion Oncogenes Are Associated With Increased Metastatic Capacity and Persistent Disease in Pediatric Thyroid Cancers

PURPOSE

In 2014, data from a comprehensive multiplatform analysis of 496 adult papillary thyroid cancer samples reported by The Cancer Genome Atlas project suggested that reclassification of thyroid cancer into molecular subtypes, RAS-like and BRAF-like, better reflects clinical behavior than sole reliance on pathologic classification. The aim of this study was to categorize the common oncogenic variants in pediatric differentiated thyroid cancer (DTC) and investigate whether mutation subtype classification correlated with the risk of metastasis and response to initial therapy in pediatric DTC.

METHODS

Somatic cancer gene panel analysis was completed on DTC from 131 pediatric patients. DTC were categorized into RAS-mutant (H-K-NRAS), BRAF-mutant (BRAF p.V600E), and RET/NTRK fusion (RET, NTRK1, and NTRK3 fusions) to determine differences between subtype classification in regard to pathologic data (American Joint Committee on Cancer TNM) as well as response to therapy 1 year after initial treatment had been completed.

RESULTS

Mutation-based subtype categories were significant in most variables, including age at diagnosis, metastatic behavior, and the likelihood of remission at 1 year. Patients with RET/NTRK fusions were significantly more likely to have advanced lymph node and distant metastasis and less likely to achieve remission at 1 year than patients within RAS- or BRAF-mut subgroups.

CONCLUSION

Our data support that genetic subtyping of pediatric DTC more accurately reflects clinical behavior than sole reliance on pathologic classification with patients with RET/NTRK fusions having worse outcomes than those with BRAF-mutant disease. Future trials should consider inclusion of molecular subtype into risk stratification.

Poorly differentiated thyroid carcinoma: a clinician's perspective

Poorly differentiated thyroid carcinoma (PDTC) is a rare thyroid carcinoma originating from follicular epithelial cells. No explicit consensus can be achieved to date due to sparse clinical data, potentially compromising the outcomes of patients. In this comprehensive review from a clinician's perspective, the epidemiology and prognosis are described, diagnosis based on manifestations, pathology, and medical imaging are discussed, and both traditional and emerging therapeutics are addressed as well. Turin consensus remains the mainstay diagnostic criteria for PDTC, and individualized assessments are decisive for treatment option. The prognosis is optimal if complete resection is performed at early stage but dismal in nearly half of patients with locally advanced and/or distant metastatic diseases, in which adjuvant therapies such as 131I therapy, external beam radiation therapy, and chemotherapy should be incorporated. Emerging therapeutics including molecular targeted therapy, differentiation therapy, and immunotherapy deserve further investigations to improve the prognosis of PDTC patients with advanced disease.

Real-World Experience of NTRK Fusion-Positive Thyroid Cancer

Trk inhibition led to durable responses in 3/4 patients with NTRK fusion+ thyroid cancer including a novel ETV6-NTRK2 fusion.

Thyroid Cancer and COVID-19: Prospects for Therapeutic Approaches and Drug Development

Thyroid cancer is the most prevalent endocrine malignancy and the reported incidence of thyroid cancer has continued to increase in recent years. Since 2019, coronavirus disease 2019 (COVID-19) has been spreading worldwide in a global pandemic. COVID-19 aggravates primary illnesses and affects disease management; relevant changes include delayed diagnosis and treatment. The thyroid is an endocrine organ that is susceptible to autoimmune attack; thus, thyroid cancer after COVID-19 has gradually attracted attention. Whether COVID-19 affects the diagnosis and treatment of thyroid cancer has also attracted the attention of many researchers. This review examines the literature regarding the influence of COVID-19 on the pathogenesis, diagnosis, and treatment of thyroid cancer; it also focuses on drug therapies to promote research into strategies for improving therapy and management in thyroid cancer patients with COVID-19.

[Molecular genotyping in refractory thyroid cancers in 2021: When, how and why? A review from the TUTHYREF network]

Refractory thyroid cancers include radio-iodine-refractory cancers, metastatic or locally advanced unresectable medullary and anaplastic thyroid cancers. Their management has been based for several years on the use of multi-target kinase inhibitors, with anti-angiogenic action, with the exception of anaplastic cancers usually treated with chemo- and radiotherapy. The situation has recently evolved due to the availability of molecular genotyping techniques allowing the discovery of rare but targetable molecular abnormalities. New treatment options have become available, more effective and less toxic than the previously available multi-target kinase inhibitors. The management of refractory thyroid cancers is therefore becoming more complex both at a diagnosis level with the need to know when, how and why to look for these molecular abnormalities but also at a therapeutic level, innovative treatments being hardly accessible. The cost of molecular analyzes and the access to treatments need also to be homogenized because disparities could lead to inequality of care at a national or international level. Finally, the strategy of identifying molecular alterations and treating these rare tumors reinforces the importance of a discussion in a multidisciplinary consultation meeting.

Advances in Functional Imaging of Differentiated Thyroid Cancer

Simple Summary

Since the 1940s, radioactive iodine has been used for functional imaging and for treating patients with differentiated thyroid cancer (DTC). During this long-lasting experience, the use of iodine isotopes evolved, especially during the last years due to improved knowledge of thyroid cancer biology and improved performances of imaging tools. The present review summarizes recent advances in the field of functional imaging and theragnostic approach of DTC.

Abstract

The present review provides a description of recent advances in the field of functional imaging that takes advantage of the functional characteristics of thyroid neoplastic cells (such as radioiodine uptake and FDG uptake) and theragnostic approach of differentiated thyroid cancer (DTC). Physical and biological characteristics of available radiopharmaceuticals and their use with state-of-the-art technologies for diagnosis, treatment, and follow-up of DTC patients are depicted. Radioactive iodine is used mostly with a therapeutic intent, while PET/CT with ¹⁸F-FDG emerges as a useful tool in the diagnostic management and complements the use of radioactive iodine. Beyond ¹⁸F-FDG PET/CT, other tracers including ¹²⁴I, ¹⁸F-TFB and ⁶⁸Ga-PSMA, and new methods such as PET/MR, might offer new opportunities in selecting patients with DTC for specific imaging modalities or treatments.

Oncogene-specific inhibition in the treatment of advanced pediatric thyroid cancer

Papillary thyroid cancer (PTC) is the most common form of differentiated thyroid cancer in the pediatric population and represents the second most common malignancy in adolescent females. Historically, PTC has been classified on the basis of histology, however, accumulating data indicate that molecular subtyping based on somatic oncogenic alterations along with gene expression profiling can better predict clinical behavior and may provide opportunities to incorporate oncogene-specific inhibitory therapy to improve the response to radioactive iodine (RAI). In this issue of the JCI, Y.A. Lee, H. Lee, and colleagues showed that oncogenic fusions were more commonly associated with invasive disease, increased expression of MAPK signaling pathway genes (ERK score), and decreased expression of the sodium-iodine symporter, which was restored by RET- and NTRK-inhibitory therapy. These findings lend credence to the idea of reclassifying pediatric thyroid cancers using a three-tiered system, rather than the two-tiered adult system, and open avenues for the treatment of progressive, RAI-refractory PTC in patients.

Management of Anaplastic and Recurrent Differentiated Thyroid Cancer: Indications for Surgical Resection, Molecular Testing, and Systemic Therapy

Differentiated and anaplastic thyroid cancer are tumors derived from follicular thyroid cancers and are clinically and genetically distinct. Treatment of these tumors has evolved over the past decade, with 6 drugs/drug combinations that are US Food and Drug Administration approved.

Pursuing Precision: Receptor Tyrosine Kinase Inhibitors for Treatment of Pediatric Solid Tumors

Receptor tyrosine kinases are critical for the growth and proliferation of many different cancers and therefore represent a potential vulnerability that can be therapeutically exploited with small molecule inhibitors. Over forty small molecule inhibitors are currently approved for the treatment of adult solid tumors. Their use has been more limited in pediatric solid tumors, although an increasing number of single-agent and combination studies are now being performed. These agents have been quite successful in certain clinical contexts, such as the treatment of pediatric tumors driven by kinase fusions or activating mutations. By contrast, only modest activity has been observed when inhibitors are used as single agents for solid tumors that do not have genetically defined alterations in the target genes. The absence of predictive biomarkers has limited the wider applicability of these drugs and much work remains to define the appropriate patient population and clinical situation in which receptor tyrosine kinase inhibitors are most beneficial. In this manuscript, we discuss these issues by highlighting past trials and identifying future strategies that may help add precision to the use of these agents for pediatric extracranial solid tumors.

NTRK- and RET-fusion-directed therapy in pediatric thyroid cancer yields a tumor response and radioiodine uptake

BACKGROUND

Molecular characterization in pediatric papillary thyroid cancer (PTC), distinct from adult PTC, is important for developing molecular targeted therapies for progressive 131I-refractory PTC.

METHODS

PTC samples from 106 pediatric patients (age: 4.3-19.8 years; 21 boys) who attended Seoul National University Hospital (January 1983-March 2020) were available for genomic profiling. Previous transcriptome data from 125 adult PTCs were used for comparison.

RESULTS

Genetic drivers were found in 80 tumors; 31 with fusion oncogenes (RET in 21, ALK in 6, and NTRK1/3 in 4), 47 with point mutations (BRAFV600E in 41, TERTC228T in 2, and DICER1 variants in 5), and 2 with amplifications. Fusion-oncogene PTCs, predominantly detected in younger patients, presented with a more advanced stage and showed more recurrent or persistent disease than BRAFV600E PTCs, which were detected mostly in adolescents. Pediatric fusion PTCs (in those aged < 10 years) showed lower expression of thyroid differentiation genes, including SLC5A5, than adult fusion PTCs. Two girls with progressive 131I-refractory lung metastases harboring a TPR-NTRK1 or CCDC6-RET fusion received fusion-targeted therapy; larotrectinib and selpercatinib decreased the tumor extent and restored radioiodine uptake. The girl with the CCDC6-RET fusion received 131I therapy combined with selpercatinib, leading to a tumor response. In vitro 125I uptake and 131I clonogenic assays showed that larotrectinib inhibited growth and restored radioiodine avidity.

CONCLUSIONS

In pediatric fusion-oncogene PTC cases with 131I-refractory advanced disease, selective fusion-directed therapy may restore radioiodine avidity and lead to a dramatic tumor response, underscoring the importance of molecular testing in pediatric PTC patients.

FUNDING

The Ministry of Science, ICT & Future Planning (grant number NRF-2016R1A2B4012417 91 and 2019R1A2C2084332), the Ministry of Health & Welfare, Republic of Korea (grant number 92 H14C1277), the Ministry of Education (grant number 2020R1A6A1A03047972), and the Seoul 93 National University Hospital Research Fund (grant number 04-2015-0830).

Clinical pharmacology and drug-drug interactions of lenvatinib in thyroid cancer

Lenvatinib is a non-selective tyrosine kinase inhibitor (TKI) with high in vitro potency against vascular endothelial growth factor receptors. Although this drug is used to treat several cancer types, it is the most effective TKI used in patients with thyroid cancer. Lenvatinib is well tolerated and the most common adverse drug reactions can be adequately managed by dose adjustment. Particularly, blood pressure and cardiac function monitoring, as well as antihypertensive treatment optimization, may be required in patients treated with lenvatinib. Dose reduction should be taken into account in patients with body weight <60 kg or severe hepatic failure. No significant change in lenvatinib pharmacokinetics has been observed with other patient-related factors and very few data are available on lenvatinib pharmacogenetics. Lenvatinib can be administered orally regardless of food and no clinically relevant drug-drug interactions have been reported.

Thyroid Cancers: From Surgery to Current and Future Systemic Therapies through Their Molecular Identities

Differentiated thyroid cancers (DTC) are commonly and successfully treated with total thyroidectomy plus/minus radioiodine therapy (RAI). Medullary thyroid cancer (MTC) is only treated with surgery but only intrathyroidal tumors are cured. The worst prognosis is for anaplastic (ATC) and poorly differentiated thyroid cancer (PDTC). Whenever a local or metastatic advanced disease is present, other treatments are required, varying from local to systemic therapies. In the last decade, the efficacy of the targeted therapies and, in particular, tyrosine kinase inhibitors (TKIs) has been demonstrated. They can prolong the disease progression-free survival and represent the most important therapeutic option for the treatment of advanced and progressive thyroid cancer. Currently, lenvatinib and sorafenib are the approved drugs for the treatment of RAI-refractory DTC and PDTC while advanced MTC can be treated with either cabozantinib or vandetanib. Dabrafenib plus trametinib is the only approved treatment by FDA for BRAFV600E mutated ATC. A new generation of TKIs, specifically for single altered oncogenes, is under evaluation in phase 2 and 3 clinical trials. The aim of this review was to provide an overview of the current and future treatments of thyroid cancer with regards to the advanced and progressive cases that require systemic therapies that are becoming more and more targeted on the molecular identity of the tumor.

Novel Therapeutics in Radioactive Iodine-Resistant Thyroid Cancer

Iodine-resistant cancers account for the vast majority of thyroid related mortality and, until recently, there were limited therapeutic options. However, over the last decade our understanding of the molecular foundation of thyroid function and carcinogenesis has driven the development of many novel therapeutics. These include FDA approved tyrosine kinase inhibitors and small molecular inhibitors of VEGFR, BRAF, MEK, NTRK and RET, which collectively have significantly changed the prognostic outlook for this patient population. Some therapeutics can re-sensitize de-differentiated cancers to iodine, allowing for radioactive iodine treatment and improved disease control. Remarkably, there is now an FDA approved treatment for BRAF-mutated patients with anaplastic thyroid cancer, previously considered invariably and rapidly fatal. The treatment landscape for iodine-resistant thyroid cancer is changing rapidly with many new targets, therapeutics, clinical trials, and approved treatments. We provide an up-to-date review of novel therapeutic options in the treatment of iodine-resistant thyroid cancer.

The molecular and gene/miRNA expression profiles of radioiodine resistant papillary thyroid cancer

Background

Papillary thyroid cancer (PTC) is the most frequent endocrine tumor. Radioiodine (RAI) treatment is highly effective in these tumors, but up to 60% of metastatic cases become RAI-refractory. Scanty data are available on either the molecular pattern of radioiodine refractory papillary thyroid cancers (PTC) or the mechanisms responsible for RAI resistance.

Methods

We analyzed the molecular profile and gene/miRNA expression in primary PTCs, synchronous and RAI-refractory lymph node metastases (LNMs) in correlation to RAI avidity or refractoriness.

We classified patients as RAI+/D+ (RAI uptake/disease persistence), RAI−/D+ (absent RAI uptake/disease persistence), and RAI+/D- (RAI uptake/disease remission), and analyzed the molecular and gene/miRNA profiles, and the expression of thyroid differentiation (TD) related genes.

Results

A different molecular profile according to the RAI class was observed: BRAF^V600E cases were more frequent in RAI−/D+ (P = 0.032), and fusion genes in RAI+/D+ cases. RAI+/D- patients were less frequently pTERT mutations positive, and more frequently wild type for the tested mutations/fusions. Expression profiles clearly distinguished PTC from normal thyroid. On the other hand, in refractory cases (RAI+/D+ and RAI−/D+) no distinctive PTC expression patterns were associated with either tissue type, or RAI uptake, but with the driving lesion and BRAF−/RAS-like subtype. Primary tumors and RAI-refractory LNMs with BRAF^V600E mutation display transcriptome similarity suggesting that RAI minimally affects the expression profiles of RAI-refractory metastases. Molecular profiles associated with the expression of TPO, SLC26A4 and TD genes, that were found more downregulated in BRAF^V600E than in gene fusions tumors.

Conclusions

The present data indicate a different molecular profile in RAI-avid and RAI-refractory metastatic PTCs. Moreover, BRAF^V600E tumors displayed reduced differentiation and intrinsic RAI refractoriness, while PTCs with fusion oncogenes are RAI-avid but persistent, suggesting different oncogene-driven mechanisms leading to RAI refractoriness.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01757-x.