Drug insight: Small-molecule inhibitors of protein kinases in the treatment of thyroid cancer

Selpercatinib Treatment of RET-Mutated Thyroid Cancers Is Associated With Gastrointestinal Adverse Effects

CONTEXT

Metastatic medullary thyroid carcinoma (MTC) and radioactive iodine-refractory differentiated thyroid carcinoma (RAI-R DTC) have poor prognosis and limited treatment options. Selpercatinib (LOXO-292), a selective kinase inhibitor targeting the RET gene, has shown a 69% to 79% objective response rate in this cohort with benefits in other tumors including lung cancer harboring the same oncogenic driver. Published reports describe only 17% of patients experiencing gastrointestinal (GI) adverse effects (AEs), which is in contrast to our local experience.

OBJECTIVE

Here we characterize the AEs and correlate them with radiological and histopathological findings.

METHODS

Sequential patients enrolled in LIBRETTO-001 at Royal North Shore Hospital, Sydney, Australia, with available imaging (n = 22) were recruited. Patients had regular visits with AEs documented and computed tomography (CT) scans every 3 months. CT at screening, at time of GI AE, and at most recent follow-up were reviewed and scored. Endoscopic examination was performed in 5 patients.

RESULTS

Of 22 patients in this cohort, the majority had somatic RET alterations (n = 18), most commonly p.Met918Thr (n = 14). Ten patients (50%) developed GI AEs. Dose reduction was required in 8 of the 10 patients, but none discontinued therapy. The majority had stable disease (n = 17). Gastric and small-bowel edema was evident in symptomatic patients after a median time of 67 weeks' treatment. Histological correlation in 5 patients revealed mucosal edema correlating with radiological evidence of congestion and edema.

CONCLUSION

GI AEs with selpercatinib may be more common than previously described. Most are self-limiting but often require dose adjustments. Histological evidence of mucosal edema observed in conjunction with the radiological findings of congestion and wall thickening suggest bowel-wall edema is a predominant mechanism of abdominal pain in these patients.

High Affinity Pharmacological Profiling of Dual Inhibitors Targeting RET and VEGFR2 in Inhibition of Kinase and Angiogeneis Events in Medullary Thyroid Carcinoma

Clinical evidence shows that dual inhibition of kinases as well angiogenesis provides ideal therapeutic option in the treatment of medullary thyroid carcinoma (MTC) than inhibiting either of these with the events separately. Although treatment with dual inhibitors has shown good clinical responses in patients with MTC, it has been associated with serious side effects. Some inhibitors are active agents for both angiogenesis or kinase activity. Owing to narrow therapeutic window of established inhibitors, the present study aims to identify high affinity dual inhibitors targeting RET and VEGFR2 respectively for kinase and angiogenesis activity. Established inhibitors like Vandetanib, Cabozantinib, Motesanib, PP121, RAF265 and Sunitinib served as query parent compounds for identification of structurally similar compounds by Tanimoto-based similarity searching with a threshold of 95% against the PubChem database. All the parent inhibitors and respective similar compounds were docked against RET and VEGFR2 in order to retrieve high affinity compounds with these two proteins. AGN-PC-0CUK9P PubCID: 59320403 a compound related to PPI21 showed almost equal affinity for RET and VEGFR2 and unlike other screened compounds with no apparent bias for either of the receptors. Further, AGN- PC-0CUK9P demonstrated appreciable interaction with both RET and VEGFR2 and superior kinase activity in addition to showed optimal ADMET properties and pharmacophore features. From our in silico investigation we suggest AGN-PC-0CUK9P as a superior dual inhibitor targeting RET and VEGFR2 with high efficacy which should be proposed for pharmacodynamic and pharmacokinetic studies for improved treatment of MTC.

Identification of selective inhibitors of RET and comparison with current clinical candidates through development and validation of a robust screening cascade

RET (REarranged during Transfection) is a receptor tyrosine kinase, which plays pivotal roles in regulating cell survival, differentiation, proliferation, migration and chemotaxis. Activation of RET is a mechanism of oncogenesis in medullary thyroid carcinomas where both germline and sporadic activating somatic mutations are prevalent. At present, there are no known specific RET inhibitors in clinical development, although many potent inhibitors of RET have been opportunistically identified through selectivity profiling of compounds initially designed to target other tyrosine kinases. Vandetanib and cabozantinib, both multi-kinase inhibitors with RET activity, are approved for use in medullary thyroid carcinoma, but additional pharmacological activities, most notably inhibition of vascular endothelial growth factor - VEGFR2 (KDR), lead to dose-limiting toxicity. The recent identification of RET fusions present in ~1% of lung adenocarcinoma patients has renewed interest in the identification and development of more selective RET inhibitors lacking the toxicities associated with the current treatments. In an earlier publication [Newton et al, 2016; 1] we reported the discovery of a series of 2-substituted phenol quinazolines as potent and selective RET kinase inhibitors. Here we describe the development of the robust screening cascade which allowed the identification and advancement of this chemical series.  Furthermore we have profiled a panel of RET-active clinical compounds both to validate the cascade and to confirm that none display a RET-selective target profile.

Identification of selective inhibitors of RET and comparison with current clinical candidates through development and validation of a robust screening cascade

RET (REarranged during Transfection) is a receptor tyrosine kinase, which plays pivotal roles in regulating cell survival, differentiation, proliferation, migration and chemotaxis. Activation of RET is a mechanism of oncogenesis in medullary thyroid carcinomas where both germline and sporadic activating somatic mutations are prevalent. At present, there are no known specific RET inhibitors in clinical development, although many potent inhibitors of RET have been opportunistically identified through selectivity profiling of compounds initially designed to target other tyrosine kinases. Vandetanib and cabozantinib, both multi-kinase inhibitors with RET activity, are approved for use in medullary thyroid carcinoma, but additional pharmacological activities, most notably inhibition of vascular endothelial growth factor - VEGFR2 (KDR), lead to dose-limiting toxicity. The recent identification of RET fusions present in ~1% of lung adenocarcinoma patients has renewed interest in the identification and development of more selective RET inhibitors lacking the toxicities associated with the current treatments. In an earlier publication [Newton et al, 2016; 1] we reported the discovery of a series of 2-substituted phenol quinazolines as potent and selective RET kinase inhibitors. Here we describe the development of the robust screening cascade which allowed the identification and advancement of this chemical series.  Furthermore we have profiled a panel of RET-active clinical compounds both to validate the cascade and to confirm that none display a RET-selective target profile.

Use of Vandetanib in Metastatic Medullary Carcinoma of Thyroid in a Pediatric Patient With Multiple Endocrine Neoplasia 2B

We describe a child with advanced, metastatic, inoperable medullary carcinoma of thyroid associated with multiple endocrine neoplasia 2B and rearranged during transfection mutation with a positive response to vandetanib treatment. He responded well with a fall in calcitonin levels and a reduction in size of the thyroid malignancy, lymph nodes, and pulmonary metastases. He has been on vandetanib for 4 years with good clinical and biochemical response. Vandetanib has a role in the treatment of patients including children with inoperable locally advanced and metastatic medullary carcinoma of thyroid. More information is needed on its use in children and long-term outcome.

Quercetin-Induced Cell Death in Human Papillary Thyroid Cancer (B-CPAP) Cells

In this study, we have investigated the antiproliferative effect of quercetin on human papillary thyroid cancer cells and determined the apoptotic mechanisms underlying its actions. We have used different concentrations of quercetin to induce apoptosis and measured cell viability. Apoptosis and cell cycle analysis was determined by flow cytometry using Annexin V and propidium iodide. Finally, we have measured changes in caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) protein expression levels as hallmarks of apoptosis and Hsp90 protein expression level as a marker of proteasome activity in treated and control cells. Quercetin treatment of human papillary thyroid cancer cells resulted in decreased cell proliferation and increased rate of apoptosis by caspase activation. Furthermore, it was demonstrated that quercetin induces cancer cell apoptosis by downregulating the levels of Hsp90. In conclusion, we have shown that quercetin induces downregulation of Hsp90 expression that may be involved in the decrease of chymotrypsin-like proteasome activity which, in order, induces inhibition of growth and causes cell death in thyroid cancer cells. Thus, quercetin appears to be a promising candidate drug for Hsp90 downregulation and apoptosis of thyroid cancer cells.

Identification of Novel Small Molecule Inhibitors of Oncogenic RET Kinase

Oncogenic mutation of the RET receptor tyrosine kinase is observed in several human malignancies. Here, we describe three novel type II RET tyrosine kinase inhibitors (TKI), ALW-II-41-27, XMD15-44 and HG-6-63-01, that inhibit the cellular activity of oncogenic RET mutants at two digit nanomolar concentration. These three compounds shared a 3-trifluoromethyl-4-methylpiperazinephenyl pharmacophore that stabilizes the ‘DFG-out’ inactive conformation of RET activation loop. They blocked RET-mediated signaling and proliferation with an IC50 in the nM range in fibroblasts transformed by the RET/C634R and RET/M918T oncogenes. They also inhibited autophosphorylation of several additional oncogenic RET-derived point mutants and chimeric oncogenes. At a concentration of 10 nM, ALW-II-41-27, XMD15-44 and HG-6-63-01 inhibited RET kinase and signaling in human thyroid cancer cell lines carrying oncogenic RET alleles; they also inhibited proliferation of cancer, but not non-tumoral Nthy-ori-3-1, thyroid cells, with an IC50 in the nM range. The three compounds were capable of inhibiting the ‘gatekeeper’ V804M mutant which confers substantial resistance to established RET inhibitors. In conclusion, we have identified a type II TKI scaffold, shared by ALW-II-41-27, XMD15-44 and HG-6-63-01, that may be used as novel lead for the development of novel agents for the treatment of cancers harboring oncogenic activation of RET.

Functional characterization of a novel FGFR1OP-RET rearrangement in hematopoietic malignancies

The RET (REarranged during Transfection) receptor tyrosine kinase is targeted by oncogenic rearrangements in thyroid and lung adenocarcinoma. Recently, a RET (exon 12) rearrangement with FGFR1OP [fibroblast growth factor receptor 1 (FGFR1) oncogene partner] (exon 12) was identified in one chronic myelomonocytic leukemia (CMML) patient. We report the molecular cloning and functional characterization of a novel FGFR1OP (exon 11)-RET (exon 11) gene fusion event (named FGFR1OP-RET), mediated by a reciprocal translocation t(6; 10)(q27; q11), in a patient affected by primary myelofibrosis (PMF) with secondary acute myeloid leukemia (AML). The FGFR1OP-RET fusion protein displayed constitutive tyrosine kinase and transforming activity in NIH3T3 fibroblasts, and induced IL3-independent growth and activation of PI3K/STAT signaling in hematopoietic Ba/F3 cells. FGFR1OP-RET supported cytokine-independent growth, protection from stress and enhanced self-renewal of primary murine hematopoietic progenitor and stem cells in vitro. In vivo, FGFR1OP-RET caused a spectrum of disease phenotypes, with >50% of mice showing a fatal myeloproliferative disorder (MPD). Other phenotypes were leukemia transplantable in secondary recipients, dramatic expansion of the mast cell lineage, and reduction of repopulating activity upon lethal irradiation. In conclusion, FGFR1OP-RET chimeric oncogenes are endowed with leukemogenic potential and associated to myeloid neoplasms (CMML and PMF/AML).

Oncogenic rearrangements driving ionizing radiation-associated human cancer

The Chernobyl nuclear disaster has caused a remarkable increase in radiation-induced papillary thyroid carcinoma in children and young adults. In this issue of the JCI, Ricarte-Filho and colleagues demonstrate that chromosomal rearrangements are the oncogenic "drivers" in most post-Chernobyl carcinomas and that they often lead to unscheduled activation of the MAPK signaling pathway. These findings represent a major step forward in our understanding of radiation-induced carcinogenesis and suggest various hypotheses about the mechanisms underlying the formation and selection of gene rearrangements during cancer cell evolution.

Vandetanib: opening a new treatment practice in advanced medullary thyroid carcinoma

Medullary thyroid cancer (MTC) is frequently diagnosed in a locally advanced or metastatic stage, and 10-year survival rates in these cases are below 20 %. Cytotoxic chemotherapy has no significant impact on overall or progression-free survival. Vandetanib (Caprelsa(®), AstraZeneca) is a once-daily oral tyrosine kinase inhibitor that selectively inhibits signalling mediated by growth-factor receptor tyrosine kinase RET (constitutively activated in roughly 60 % of all MTCs), vascular endothelial growth-factor receptors 2 and 3, and epidermal growth-factor receptors. It is the first systemic drug with demonstrated anti-tumor benefits in advanced MTC, and it has recently been approved for locally advanced or metastatic MTC by the United States Food and Drug Administration (April 2011) and the European Medicines Agency (February 2012). This review, starting from the phases II and III efficacy and safety data that led to these approvals, explores important issues related to dosing, patient selection, and strategies for managing the substantial risk of toxicity associated with the drug (including life-threatening cardiac events that are the subject of a black-box warning in the United States). All these issues still remain to be defined. Vandetanib is becoming a standard of care for symptomatic, progressive, metastatic MTCs, to be used selectively in those patients who are likely to benefit from it.

A Phase I study of the combination of oxaliplatin/docetaxel and vandetanib for the treatment of advanced gastroesophageal cancer

INTRODUCTION

This study aimed to assess the safety and tolerability of the multitargeted tyrosine kinase inhibitor, vandetanib (V), in combination with two chemotherapeutic agents, oxaliplatin (O) and docetaxel (D) in advanced gastroesophageal (GE) cancer.

METHODS

This was a Phase I study (NCT00732745) with a standard 3+3 dose escalation design. The primary aim was to determine the optimal dose of the combination of vandetanib and OD chemotherapy.

RESULTS

Initial treatment for the first cohort consisted of oxaliplatin at 100 mg/m2 on day 1, docetaxel at 35 mg/m2 on days 1 and 8 and vandetanib 100 mg PO daily of 21-day treatment cycles. As dose limiting toxicity (DLT) was reached in 2 out of 3 patients in cohort 1 (one grade 3 and one grade 4 diarrhea with dehydration), 6 patients were treated then at dose level -1 (O 80 mg/m2 on day 1, D 30 mg/m2 on days 1 and 8, V 100 mg PO daily days 1-21) in which no further DLTs were observed. This dose was established as maximum tolerated dose and is the recommended phase 2 dose. 8 out of 9 enrolled patients had adenocarcinoma. At dose level 1, 1 of the 3 patients had a documented partial response and 2 patients had stable disease. At dose level -1, 1 of 6 patients achieved a complete response, 2 of 6 patients had stable disease, and 3 of 6 patients had progressive disease.

CONCLUSIONS

Vandetanib added to oxaliplatin and docetaxel showed manageable toxicity and limited activity in advanced GE cancer.

A novel combination of withaferin A and sorafenib shows synergistic efficacy against both papillary and anaplastic thyroid cancers

BACKGROUND

Sorafenib (SO), a multikinase-targeted inhibitor in clinical trials for papillary and anaplastic cancers, shows limited efficacy with moderate toxicity. Withaferin A (WA), a natural withanolide, shows potent preclinical anticancer activity in thyroid cancers through multiple cytotoxic mechanisms including heat-shock protein inhibition. We hypothesized that combination therapy (WA + SO) would have a synergistic effect against anaplastic and papillary carcinoma cells at lower sorafenib doses.

METHODS

Human papillary (BCPAP) and anaplastic (SW1736) thyroid cancer cell lines were evaluated after treatment with SO, WA, or their combination at different doses. Proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and trypan blue exclusion; apoptosis and cell-cycle arrest was measured by flow cytometry. Western analysis confirmed apoptosis (Poly ADP ribose polymerase [PARP] and caspase-3 cleavage) and Raf inhibition. Experiments were repeated in triplicate and were evaluated statistically with significance set at a P value of less than .05.

RESULTS

The concentration of drug at which 50% of the cells are inhibited (IC(50)) in BCPAP were 6.3 μmol/L (SO), .155 μmol/L (WA), and .055 μmol/L (IC(50)WA + 50% IC(50)SO), whereas in SW1736 cells the concentration was 7.6 μmol/L (SO), 2.5 μmol/L (WA), and 1.4 μmol/L (IC(50)WA + 50% IC(50)SO). Combination (WA + SO) at IC(50) decreased cell viability to 19% (from 50% individually). Apoptosis levels on flow cytometry in anaplastic cells increased significantly from 0% to 2% (SO or WA alone) to 89% (combo at IC(50), P < .001). Combination therapy apoptosis (PARP cleavage and caspase-3 inactivation) and BRAF/Raf-1 down-regulation were dose-dependent starting at 50% IC(50) levels. Cell-cycle modulation was significant with combination treatment (35% increase in G2 arrest at 50% IC(50)SO + WA and 70% increase at 75% IC(50)SO + WA; P < .01).

CONCLUSIONS

Combination therapy with sorafenib + withaferin showed synergistic efficacy in papillary and anaplastic cancers in vitro with significant induction of apoptosis. This combination achieved potent anticancer activity with lower overall doses of sorafenib, indicating a potential strategy to decrease sorafenib toxicity in future translational studies.

Novel withanolides target medullary thyroid cancer through inhibition of both RET phosphorylation and the mammalian target of rapamycin pathway

BACKGROUND

Despite development of current targeted therapies for medullary thyroid cancer (MTC), long-term survival remains unchanged. Recently isolated novel withanolide compounds from Solanaceae physalis are highly potent against MTCs. We hypothesize that these withanolides uniquely inhibit RET phosphorylation and the mammalian target of rapamycin (mTOR) pathway in MTC cells as a mechanism of antiproliferation and apoptosis.

METHODS

MTC cells were treated with novel withanolides and MTC-targeted drugs. In vitro studies assessed cell viability and proliferation (MTS; trypan blue assays), apoptosis (flow cytometry with Annexin V/PI staining; confirmed by Western blot analysis), long-term cytotoxic effects (clonogenic assay), and suppression of key regulatory proteins such as RET, Akt, and mTOR (by Western blot analysis).

RESULTS

The novel withanolides potently reduced MTC cell viability (half maximal inhibitory concentration [IC(50)], 270-2,850 nmol/L; 250-1,380 nmol/L for vandetanib; 360-1,640 nmol/L for cabozantinib) with induction of apoptosis at <1,000 nmol/L of drug. Unique from other targeted therapies, withanolides suppressed RET and Akt phosphorylation and protein expression (in a concentration- and time-dependent manner) as well as mTOR activity and translational activity of 4E-BP1 and protein synthesis mediated by p70S6kinase activation at IC(50) concentrations.

CONCLUSION

Novel withanolides from Physalis selectively and potently inhibit MTC cells in vitro. Unlike other MTC-targeted therapies, these compounds uniquely inhibit both RET kinase activity and the Akt/mTOR prosurvival pathway. Further translational studies are warranted to evaluate their clinical potential.

Thyroid Cancer: Role of RET and Beyond

Specific thyroid cancer histotypes, such as papillary and medullary thyroid carcinoma, display genetic rearrangements or point mutations of the RET gene, resulting in its oncogenic conversion. The molecular mechanisms mediating RET rearrangement with other genes and the role of partner genes in tumorigenesis have been described. In addition, the RET protein has become a molecular target for medullary thyroid carcinoma treatment.

Vandetanib in patients with locally advanced or metastatic medullary thyroid cancer: a randomized, double-blind phase III trial

PURPOSE

There is no effective therapy for patients with advanced medullary thyroid carcinoma (MTC). Vandetanib, a once-daily oral inhibitor of RET kinase, vascular endothelial growth factor receptor, and epidermal growth factor receptor signaling, has previously shown antitumor activity in a phase II study of patients with advanced hereditary MTC.

PATIENTS AND METHODS

Patients with advanced MTC were randomly assigned in a 2:1 ratio to receive vandetanib 300 mg/d or placebo. On objective disease progression, patients could elect to receive open-label vandetanib. The primary end point was progression-free survival (PFS), determined by independent central Response Evaluation Criteria in Solid Tumors (RECIST) assessments.

RESULTS

Between December 2006 and November 2007, 331 patients (mean age, 52 years; 90% sporadic; 95% metastatic) were randomly assigned to receive vandetanib (231) or placebo (100). At data cutoff (July 2009; median follow-up, 24 months), 37% of patients had progressed and 15% had died. The study met its primary objective of PFS prolongation with vandetanib versus placebo (hazard ratio [HR], 0.46; 95% CI, 0.31 to 0.69; P < .001). Statistically significant advantages for vandetanib were also seen for objective response rate (P < .001), disease control rate (P = .001), and biochemical response (P < .001). Overall survival data were immature at data cutoff (HR, 0.89; 95% CI, 0.48 to 1.65). A final survival analysis will take place when 50% of the patients have died. Common adverse events (any grade) occurred more frequently with vandetanib compared with placebo, including diarrhea (56% v 26%), rash (45% v 11%), nausea (33% v 16%), hypertension (32% v 5%), and headache (26% v 9%).

CONCLUSION

Vandetanib demonstrated therapeutic efficacy in a phase III trial of patients with advanced MTC (ClinicalTrials.gov NCT00410761).

XL184 (cabozantinib) for medullary thyroid carcinoma

INTRODUCTION

Intrathyroidal medullary thyroid carcinoma (MTC) can generally be cured by surgery, but distant metastases are often already present at diagnosis.Currently, there is no effective treatment for metastatic MTC. In these cases, consensus treatment guidelines explicitly recommend new experimental drugs. Several kinase inhibitors are now being tested for treatment of MTC in clinical trials and XL184, an oral, small-molecule multi-kinase inhibitor, seems to be one of the most promising of these compounds.

AREAS COVERED

We review preliminary data on the safety and efficacy of XL184 in metastatic MTC based on an extensive search of the literature, which included published articles, abstracts and website information. In particular,the review focuses on the rationale for using XL184 in advanced MTC. The compound has been specifically designed to target multiple signaling pathways,and this is expected to produce synergistic antitumor effects superior to those achieved by single-kinase inhibition. Preliminary results from the Phase I study of XL184 seem to support this hypothesis.

EXPERT OPINION

Multiple receptor tyrosine kinases (RTKs) are concomitantly activated in the same tumor. The blockade of a single RTK may engage compensatory signaling that maintains cell growth. Targeting multiple kinases might overcome both intrinsic and acquired resistance to antitumoral drugs.

A novel RET inhibitor with potent efficacy against medullary thyroid cancer in vivo

BACKGROUND

Most medullary thyroid carcinomas (MTC) recur or progress despite curative resection. Current targeted therapies show promise but lack durable efficacy and tolerability. The purpose of this study was to build on previous in vitro work and evaluate withaferin A (WA), a novel RET inhibitor, in a metastatic murine model of MTC.

METHODS

A total of 5 million DRO-81-1 human MTC cells injected in the left posterior neck of nu/nu mice generated metastases uniformly to the liver, spleen, and/or lungs. Treatment with WA (8 mg/kg/day, intraperitoneally, for 21 days) was started for neoplasms > 100 mm(3). Endpoints were survival, neoplasm > 15,00 mm(3), decreased body weight, or body score (all measured three times/wk).

RESULTS

All controls (saline; n = 5) died or deteriorated from metastatic disease by 7 weeks postinjection. All treated animals were alive (WA; n = 5), having tumor regression and growth delay without toxicity or weight loss at 6 weeks posttreatment (P < .01). Tumor cells treated with WA demonstrated inhibition of total and phospho-RET levels by Western blot analysis in a dose-dependent manner (almost complete inhibition with treatment of 5 μM WA) as well as potent inhibition of phospho-ERK and phospho-Akt levels.

CONCLUSION

WA is a novel natural-product RET-inhibitor with efficacy in a metastatic murine model of MTC. Further long-term efficacy/toxicity studies are warranted to evaluate this compound for clinical translation.

New targeted molecular therapies for dedifferentiated thyroid cancer

Dedifferentiated thyroid cancer (DeTC) derived from follicular epithelium is often incurable because it does not respond to radioiodine, radiotherapy, or chemotherapy. In cases, RET/PTC rearrangements are found in 30%–40%, RAS mutations in about 10%, and BRAF mutations in around 40%–50%, with no overlap between these mutations results in papillary thyroid cancer, while a higher prevalence of BRAF mutations (up to 70%) has been observed in DeTC. The identification of these activating mutations in DeTC makes this malignancy an excellent model to examine the effect of tyrosine kinase inhibitors (TKIs). Clinical trials with several TKIs targeting RET, and to a lesser extent BRAF, and other TKRs have shown positive results, with about one-third of DeTC showing a reduction in tumor size up to 50%, with the longest treatment duration of approximately three-four years. Angiogenesis inhibitors have also shown promising activity in DeTC. Progress is being made toward effective targeted DeTC therapy. The possibility of testing the sensitivity of primary DeTC cells from each subject to different TKIs could increase the effectiveness of the treatment.

Vandetanib (100 mg) in patients with locally advanced or metastatic hereditary medullary thyroid cancer

PURPOSE

Vandetanib is a once-daily oral inhibitor of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor tyrosine kinases that also inhibits rearranged during transfection kinase activity. Vandetanib (300 mg/d) has previously demonstrated antitumor activity in patients with advanced hereditary medullary thyroid cancer (MTC). This study investigated the efficacy and safety of 100 mg/d vandetanib in patients with advanced hereditary MTC.

PATIENTS AND METHODS

Eligible patients with unresectable, measurable, locally advanced, or metastatic hereditary MTC received 100 mg/d vandetanib. Upon disease progression, eligible patients could enter postprogression treatment with 300 mg/d vandetanib until a withdrawal criterion was met. The primary objective was to assess the objective response rate by response evaluation criteria in solid tumors.

RESULTS

The study comprised 19 patients (13 males, six females; mean age 45 yr). Confirmed objective partial responses were observed in three patients, yielding an objective response rate of 16% (95% confidence interval 3.4-39.6). Stable disease lasting 24 wk or longer was reported in a further 10 patients (53%); the disease control rate was therefore 68% (95% confidence interval 43.4-87.4). Serum levels of calcitonin and carcinoembryonic antigen showed a sustained 50% or greater decrease from baseline in 16% (three of 19) and 5% (one of 19) of patients, respectively. Adverse events were predominantly grade 1 or 2 and consistent with previous vandetanib monotherapy studies.

CONCLUSIONS

Vandetanib at a once-daily dose of 100 mg has clinically relevant antitumor activity in patients with locally advanced or metastatic hereditary MTC and an overall acceptable safety profile.

Thyroid cancer: current molecular perspectives

The thyroid cancer is a rare oncological entity, representing no more than 1% of all human malignant neoplasms. Recently, it has been demonstrated a sharp increase in incidence of differentiated thyroid carcinoma, equally occurring in both sexes. So far, multiple genetic alterations have been identified in differentiated thyroid carcinoma, leading to investigate the clinical utility of genetic studies. In particular, molecular genetic approaches searching for gene mutations in the material collected by fine needle ago-biopsy may have a particular utility in small nodules and in those specimens with an indeterminate cytology. The expansion of knowledge about genetic mutations occurring in different thyroid tumors has characterized recent years, allowing the identification of a correlation between specific mutations and phenotypic characteristics of thyroid cancers, essential for their prognosis. This review will briefly report on the histological features and the new entity represented by thyroid microcarcinoma and will focus on both environmental and genetic aspects associated with the occurrence of thyroid cancer.

Partial remission of metastatic papillary thyroid carcinoma with sunitinib. Report of a case and review of the literature

Tyrosine kinase receptors have been implicated in thyroid cancer. Therefore, tyrosine kinase inhibitors may be used for the treatment of advanced metastatic thyroid carcinoma. The aim is to present a case of metastatic papillary thyroid carcinoma responding to the administration of sunitinib, a multi-targeted protein kinase inhibitor. A patient presented with metastatic papillary thyroid carcinoma and hyperthyroidism. After euthyroidism was achieved the patient was treated by the administration of therapeutic radioiodine (131)I, radiotherapy and sunitinib, a multi-targeted tyrosine kinase inhibitor. Thyroglobulin levels decreased from 9,594 to 6,816 ng/ml after 1 month, 6 months later being 2,776 ng/ml. The lesion in the pelvis was 12.5 × 9 cm before treatment decreasing thereafter and the patient improved clinically. The administration of sunitinib resulted in partial disease response in a patient with progressive metastatic papillary thyroid carcinoma. Protein kinase inhibitors may prove useful in the management of advanced metastatic papillary thyroid carcinoma.

Vandetanib for the treatment of patients with locally advanced or metastatic hereditary medullary thyroid cancer

PURPOSE There is no effective therapy for patients with distant metastasis of medullary thyroid carcinoma (MTC). Activating mutations in the RET proto-oncogene cause hereditary MTC, which provides a strong therapeutic rationale for targeting RET kinase activity. This open-label, phase II study assessed the efficacy of vandetanib, a selective oral inhibitor of RET, vascular endothelial growth factor receptor, and epidermal growth factor receptor signaling, in patients with advanced hereditary MTC. METHODS Patients with unresectable locally advanced or metastatic hereditary MTC received initial treatment with once-daily oral vandetanib 300 mg. The dose was adjusted additionally in some patients on the basis of observed toxicity until disease progression or any other withdrawal criterion was met. The primary assessment was objective tumor response (by RECIST [Response Evaluation Criteria in Solid Tumors]). Results Thirty patients received initial treatment with vandetanib 300 mg/d. On the basis of investigator assessments, 20% of patients (ie, six of 30 patients) experienced a confirmed partial response (median duration of response at data cutoff, 10.2 months). An additional 53% of patients (ie, 16 of 30 patients) experienced stable disease at >/= 24 weeks, which yielded a disease control rate of 73% (ie, 22 of 30 patients). In 24 patients, serum calcitonin levels showed a 50% or greater decrease from baseline that was maintained for at least 4 weeks; 16 patients showed a similar reduction in serum carcinoembryonic antigen levels. The most common adverse events were diarrhea (70%), rash (67%), fatigue (63%), and nausea (63%). CONCLUSION In this study, vandetanib demonstrated durable objective partial responses and disease control with a manageable adverse event profile. These results demonstrate that vandetanib may provide an effective therapeutic option in patients with advanced hereditary MTC, a rare disease for which there has been no effective therapy.

A novel HSP90 modulator with selective activity against thyroid cancers in vitro

BACKGROUND

Heat shock protein 90 (HSP90) is a chaperone protein regulating several client proteins involved in thyroid cancer development. The purpose of this study was to mechanistically evaluate a novel, natural product drug with anticancer activity in thyroid cancer cell lines in vitro for future translational applications.

METHODS

A total of 285 natural plant extracts and compounds were evaluated for anticancer activity by MTS assay. Apoptosis and cell cycle arrest were characterized by annexin V-propidium iodide (PI) flow cytometry. HSP90 and client protein modulation, as well as apoptosis confirmation, as demonstrated by Western blot analysis.

RESULTS

Of the 285 compounds and products tested, 45 demonstrated antiproliferative activity in thyroid cancers by MTS assay. BTIMNP_D004 demonstrated the greatest inhibition (IC(50) = 155-2,890 nM in thyroid cancers). Activity was cancer-cell selective compared to fibroblasts, with increased potency over 17-AAG in BCPAP, FTC133, and DRO81-1 cells. D004 modulated cell cycle arrest after 18 hours (G(1)/G(0) --> S and G(2)/M) with 30% FTC133 cells shifted, 22% BCPAP cells shifted, and 15% SW1736 cells shifted versus controls (P < .01, P < .01, and P < .05, respectively). A total of 1 muM D004 induced significant apoptosis, with 76% BCPAP cells gated after 18 hours (annexin V-PI staining vs <3% in controls, P < .01; and 80% FTC133 cells vs 4% controls; P < .01). Western blot analysis demonstrated modulation of HSP90 expression levels, with inhibition of HSF-1, AKT, and caspase-3 expression, and cleavage of PARP in both BCPAP and FTC133 cells.

CONCLUSION

BTIMNP_D004 is a novel natural product drug with anticancer activity against thyroid cancers in vitro, and may act through induction of apoptosis, modulation of cell cycle arrest, and modulation of heat shock chaperone proteins including HSP90. These preliminary in vitro data support future preclinical studies for translational applications.

Medullary thyroid carcinoma: targeted therapies and future directions

Medullary thyroid cancer (MTC) is a rare neuroendocrine neoplasm that accounts for approximately 5% of all thyroid malignancies. The natural history of MTC is characterized by early lymph node and distant metastases, making complete surgical cure often impossible. Conventional chemotherapy and external beam radiation have been largely ineffective in altering the natural history of MTC. Therefore, there is a great need to develop novel therapeutic strategies to affect symptom control and reduce tumor burden in patients with widely disseminated disease. Here, we review several pathways which have been shown to be vital in MTC tumorigenesis and focus on the pathways of interest for which targeted drug therapies are currently being developed.

Clinical trials for progressive differentiated thyroid cancer: patient selection, study design, and recent advances

Treatment of metastatic differentiated thyroid cancer is first based on the use of radioiodine and thyrotropin-suppressive thyroid hormone treatment. The recent availability of molecular-targeted therapies has lead to reconsideration of the treatment strategy in differentiated thyroid cancer patients with distant metastases who are resistant to radioiodine therapy. In those with progressive disease, treatment with kinase inhibitors should be offered preferably in the context of a prospective trial.

Clinicopathologic and molecular disease prognostication for papillary thyroid cancer

Despite its increasing incidence over the last 30 years, the mortality rate of papillary thyroid cancer (PTC) has decreased significantly. Nevertheless, a minority of patients still present with an aggressive form of PTC that can lead to death, even after a prolonged period of survival. Many classifications exist that allow one to stratify the clinical risk of recurrence and death in patients with PTC; however, the parameters upon which they are established are pathological and molecular and, therefore, are revealed only after surgery. The preoperative identification of these aggressive variants of PTC would allow one to schedule a more aggressive operation (e.g., total thyroidectomy together with central and/or mono- or bi-lateral node dissections) in patients with high-risk PTC. This article reviews the parameters used most commonly to differentiate low-risk PTCs from their more aggressive variants and describes some of the newest molecular therapies for this latter group of tumors.

Mutational profile of advanced primary and metastatic radioactive iodine-refractory thyroid cancers reveals distinct pathogenetic roles for BRAF, PIK3CA, and AKT1

Patients with poorly differentiated thyroid cancers (PDTC), anaplastic thyroid cancers (ATC), and radioactive iodine-refractory (RAIR) differentiated thyroid cancers have a high mortality, particularly if positive on [(18)F]fluorodeoxyglucose (FDG)-positron emission tomography (PET). To obtain comprehensive genetic information on advanced thyroid cancers, we designed an assay panel for mass spectrometry genotyping encompassing the most significant oncogenes in this disease: 111 mutations in RET, BRAF, NRAS, HRAS, KRAS, PIK3CA, AKT1, and other related genes were surveyed in 31 cell lines, 52 primary tumors (34 PDTC and 18 ATC), and 55 RAIR, FDG-PET-positive recurrences and metastases (nodal and distant) from 42 patients. RAS mutations were more prevalent than BRAF (44 versus 12%; P = 0.002) in primary PDTC, whereas BRAF was more common than RAS (39 versus 13%; P = 0.04) in PET-positive metastatic PDTC. BRAF mutations were highly prevalent in ATC (44%) and in metastatic tumors from RAIR PTC patients (95%). Among patients with multiple metastases, 9 of 10 showed between-sample concordance for BRAF or RAS mutations. By contrast, 5 of 6 patients were discordant for mutations of PIK3CA or AKT1. AKT1_G49A was found in 9 specimens, exclusively in metastases. This is the first documentation of AKT1 mutation in thyroid cancer. Thus, RAIR, FDG-PET-positive metastases are enriched for BRAF mutations. If BRAF is mutated in the primary, it is likely that the metastases will harbor the defect. By contrast, absence of PIK3CA/AKT1 mutations in one specimen may not reflect the status at other sites because these mutations arise during progression, an important consideration for therapies directed at phosphoinositide 3-kinase effectors.

Anaplastic thyroid cancer: molecular pathogenesis and emerging therapies

Anaplastic thyroid cancer (ATC) is a rare malignancy. While external beam radiation therapy has improved locoregional control, the median survival of approximately 4 months has not changed in more than half a century due to uncontrolled systemic metastases. The objective of this study was to review the literature in order to identify potential new strategies for treating this highly lethal cancer. PubMed searches were the principal source of articles reviewed. The molecular pathogenesis of ATC includes mutations in BRAF, RAS, catenin (cadherin-associated protein), beta 1, PIK3CA, TP53, AXIN1, PTEN, and APC genes, and chromosomal abnormalities are common. Several microarray studies have identified genes and pathways preferentially affected, and dysregulated microRNA profiles differ from differentiated thyroid cancers. Numerous proteins involving transcription factors, signaling pathways, mitosis, proliferation, cell cycle, apoptosis, adhesion, migration, epigenetics, and protein degradation are affected. A variety of agents have been successful in controlling ATC cell growth both in vitro and in nude mice xenografts. While many of these new compounds are in cancer clinical trials, there are few studies being conducted in ATC. With the recent increased knowledge of the many critical genes and proteins affected in ATC, and the extensive array of targeted therapies being developed for cancer patients, there are new opportunities to design clinical trials based upon tumor molecular profiling and preclinical studies of potentially synergistic combinatorial novel therapies.

Receptor tyrosine kinase inhibitors in thyroid cancer

Thyroid cancer is frequently associated with the oncogenic conversion of receptor tyrosine kinases (RTKs) or their downstream signalling molecules. Hence, there is a strong biological rationale for assessing the efficacy of RTK blockade to treat patients who are resistant to or not candidates for treatment with radioactive iodine. The first results of clinical trials based on the use of RTK inhibitors in thyroid cancer patients have recently been published. Here we discuss targeting of specific RTKs as a potential therapeutic strategy for the treatment of thyroid cancer.

Thyrotoxicosis during sunitinib treatment for renal cell carcinoma

CONTEXT

Sunitinib malate is an oral tyrosine kinase inhibitor used in the treatment of renal cell carcinoma (RCC) and gastrointestinal stromal tumours. Hypothyroidism has been observed in patients treated with sunitinib, but the mechanism whereby sunitinib induces hypothyroidism is unknown.

OBJECTIVE

To describe a series of six patients who developed thyrotoxicosis while on sunitinib for metastatic RCC.

SETTING

The study was conducted at Austin Health, a tertiary teaching hospital in Melbourne, Australia.

RESULTS

Two patients developed severe thyrotoxicosis within 10 weeks after commencing sunitinib. In contrast, in the four patients who presented with later onset (16-30 weeks) thyrotoxicosis, the thyrotoxicosis was relatively mild, self-limiting and rapidly progressed to hypothyroidism. These patients experienced recurrent episodes of thyrotoxicosis in temporal relation to their cyclical sunitinib treatment. One patient had cytological evidence of lymphocytic thyroiditis.

CONCLUSIONS

These findings suggest that sunitinib-induced hypothyroidism may be a consequence of preceding thyroiditis with associated transient thyrotoxicosis. As predictive factors are currently unknown, we suggest regular monitoring of thyroid function in all patients commenced on sunitinib. Clinicians treating patients with sunitinib or other similar kinase inhibitors should to be alerted to thyroid dysfunction as a potential toxicity of these agents.

Dedifferentiated thyroid cancer: a therapeutic challenge

Human papillary dedifferentiated thyroid cancer (HPDTC) represents a therapeutic dilemma. Targeted therapy (RET proto-oncogene or BRAF-targeting drugs) are promising treatments for HPDTC. Also PPARg agonists are another exciting field for redifferentiating therapy of HPDTC. However, even if many new approaches for the therapy of HPDTC are emerging, until now a significant clinical impact on survival by the use of these drugs is still lacking. In the future, the identification of patients who are likely to benefit from each therapeutic option will be important. In this view particular importance should be given to development of primary cells from the single patient by fine needle aspiration samples, as recently observed in anaplastic thyroid cancer. In fact, chemosensitivity tests in primary tumoral cells may help in detecting responsive patients and in preventing the administration of inactive drugs to those unresponsive.

New perspectives on the treatment of differentiated thyroid cancer

Even though differentiated thyroid carcinoma is a slow growing and usually curable disease, recurrence occurs in 20-40% and cellular dedifferentiation in up to 5% of cases. Conventional chemotherapy and radiotherapy have just a modest effect on advanced thyroid cancer. Therefore, dedifferentiated thyroid cancer represents a therapeutic dilemma and a critical area of research. Targeted therapy, a new generation of anticancer treatment, is planned to interfere with a specific molecular target, typically a protein that is believed to have a critical role in tumor growth or progression. Since many of the tumor-initiation events have already been identified in thyroid carcinogenesis, targeted therapy is a promising therapeutic tool for advanced thyroid cancer. Several new drugs are currently being tested in in vitro and in vivo studies and some of them are already being used in clinical trials, like small molecule tyrosine kinase inhibitors. In this review, we discuss the bases of targeted therapies, the principal drugs already tested and also options of redifferentiation therapy for thyroid carcinoma.

Dysregulated RET signaling in thyroid cancer

Numerous biologic processes and such diseases as cancer depend on activation of tyrosine kinase receptors. The RET tyrosine kinase receptor was discovered two decades ago as a transforming gene and was subsequently implicated in the formation of papillary and medullary thyroid carcinoma. This article examines the data about the mechanism of activation of downstream signal transduction pathways by RET oncoproteins. Collectively, these findings have advanced the understanding of the processes underlying thyroid carcinoma formation.

Thyroid carcinoma: molecular pathways and therapeutic targets

Thyroid cancer is the most common malignant tumor of the endocrine system. The most frequent type of thyroid malignancy is papillary carcinoma. These tumors frequently have genetic alterations leading to the activation of the mitogen-activated protein kinase (MAPK) signaling pathway. Most common mutations in papillary carcinomas are point mutations of the BRAF and RAS genes and RET/PTC rearrangement. These genetic alterations are found in >70% of papillary carcinomas and they rarely overlap in the same tumor. Most frequent alterations in follicular carcinomas, the second most common type of thyroid malignancy, include RAS mutations and PAX8-PPARgamma rearrangement. RET point mutations are crucial for the development of medullary thyroid carcinomas. Many of these mutations, particularly those leading to the activation of the MAPK pathway, are being actively explored as therapeutic targets for thyroid cancer. A number of compounds have been studied and showed antitumor effects in preclinical studies and are being tested in ongoing clinical trials.

New therapeutic approaches to treat medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) accounts for up to 8% of all thyroid cancers. Although primary surgery is curative in the vast majority of patients treated at an early stage, disease can persist or recur with deleterious effects on quality of life. Local and distant metastases can occur and are the major causes of mortality. Reoperation, embolization, and perhaps radiotherapy can improve the outcome for some patients who are not cured by primary surgery, but there is a need for novel treatments. No comprehensive clinical trial data are available on conventional cytotoxic agents for the treatment of MTC. Patients with distant metastases, in particular, might benefit from several novel compounds directed against angiogenesis and molecular targets in tumor cells, such as products of the proto-oncogene RET and mutants of it, and other signaling components. Well-conducted clinical trials are needed to assess and optimize these treatment strategies, and this article outlines how such trials should be conducted. Although RET mutations are common in hereditary MTC and can occur in some cases of sporadic MTC, knowledge of other molecular defects associated with the development of MTC should reveal new targets for therapy.

Molecular genetics of thyroid cancer: implications for diagnosis, treatment and prognosis

Thyroid cancer is the most common malignant tumor of the endocrine system and accounts for approximately 1% of all newly diagnosed cancer cases. The most frequent type of thyroid malignancy is papillary carcinoma, which constitutes approximately 80% of all cases. Papillary carcinomas frequently have genetic alterations leading to the activation of the MAPK signal pathway. Those include RET/PTC rearrangement and point mutations of the BRAF and RAS genes. Mutations in these genes are found in over 70% of papillary carcinomas and they rarely overlap in the same tumor. Frequent genetic alterations in follicular carcinomas, the second most common type of thyroid malignancy, include RAS mutations and PAX8-PPAR gamma rearrangement. RET point mutations are crucial for the development of medullary thyroid carcinomas. Many of these mutations, particularly those leading to the activation of the MAPK pathway, are being actively explored as therapeutic targets for thyroid cancer. Detection of these genetic alterations using molecular techniques is important for preoperative fine-needle aspiration diagnosis, prognosis and treatment of thyroid cancer.

Growth inhibition of medullary thyroid carcinoma cells by pyrazolo-pyrimidine derivates

There is no effective treatment for recurrent or metastatic medullary thyroid carcinoma (MTC), a tumor arising from thyroid C-cells commonly presenting an inherited or acquired RET mutation. In this study we examined the sensitivity of two human MTC cell lines to novel pyrazolopyrimidine derivates, able to inhibit src-family tyrosine kinase activity. In TT cells [carrying the multiple endocrine neoplasia (MEN)2A Ret mutation Cys 634Trp] and MZ-CRC-1 cells (carrying the MEN2B RET mutation Met891Thr), one of these compounds, namely Si 34, determined a significant growth inhibitory effect (approximately 90% vs control for TT, 80% vs control for MZ-CRC-1) mainly due to enhanced cell mortality after a 6-day incubation. At concentrations that increased cell mortality, neither biochemical or morphological characteristics of apoptosis were detected in TT and MZCRC- 1 cells treated with Si 34. These results, when confirmed in other in vivo preclinical models, suggest that this novel tyrosine kinase inhibitor may be useful for the treatment of MTC.

The heterogeneous distribution of BRAF mutation supports the independent clonal origin of distinct tumor foci in multifocal papillary thyroid carcinoma

CONTEXT

Papillary thyroid carcinoma (PTC) is frequently multifocal. Independent PTC foci may occur either from intraglandular metastases from a single dominant tumor or as unrelated neoplastic clones. In rare cases, the simultaneous presence of PTC foci of different histopathological subtypes points to independent sites of tumor formation.

OBJECTIVES

We examined the pattern of BRAF mutations in noncontiguous tumor foci and node metastases from 69 patients affected by multicentric PTC. These included 19 cases characterized by the simultaneous presence of different PTC histopathological variants.

DESIGN

BRAF (exon 15) mutation was examined by PCR-single strand conformational polymorphism followed by DNA sequencing in laser-capture microdissected tissue samples.

RESULTS

Discordant patterns of BRAF mutation were found in about 40% of the multifocal PTCs. In node metastases, BRAF mutations were, in most but not all the cases, concordant with the dominant tumor. A discordant pattern of BRAF mutation was also found in about 50% of the cases in which multiple foci of different histopathological variants were present.

CONCLUSIONS

The heterogeneous distribution of BRAF mutations suggests that discrete tumor foci in multifocal PTC may occur as independent tumors. This information has to be considered in the design of targeted therapeutic approaches with BRAF pathway inhibitors.

Medullary thyroid cancer: monitoring and therapy

This article summarizes the clinical features and molecular pathogenesis of medullary thyroid cancer (MTC) and focuses on the current use of molecular, biochemical, and imaging disease markers as a basis for selection of appropriate therapy. Clinicians treating patients who have MTC face the following challenges: (1) distinguishing MTC as early as possible from benign nodular disease and differentiated thyroid cancer to choose the appropriate initial surgery, (2) managing low-level residual cancer in otherwise asymptomatic individuals, and (3) treating progressive metastatic disease. Early clinical trials using small molecules targeting Ret or vascular endothelial growth factor receptors suggest that such approaches could be effective and well tolerated. This article highlights early progress in targeted therapy of MTC and significant challenges in disease monitoring to appropriately select and evaluate patients being treated with these therapies.

Efficacy of imatinib mesylate in advanced medullary thyroid carcinoma

OBJECTIVE

Medullary thyroid carcinoma (MTC) is often associated with gain-of-function mutations in the RET proto-oncogene, which is found in all hereditary cases and most sporadic cases. The activated RET receptor tyrosine kinase can be inhibited by tyrosine kinase inhibitors in vitro. We evaluated the efficacy of treatment with imatinib mesylate, a tyrosine kinase inhibitor, in patients with advanced MTC.

DESIGN AND PATIENTS

In this open-label clinical trial, nine patients, eight with sporadic and one with hereditary MTC, with unresectable, measurable, progressive metastases were treated with imatinib mesylate 600 mg daily. The tumour response to imatinib was evaluated after 3, 6 and 12 months by computed tomography and after 1 month by (18)F-fluoro-2-deoxy D-glucose position-emission tomographic scanning. The median duration of therapy was 8 months.

RESULTS

Overall, stable disease occurred in five patients for up to 6 months and in one patient for up to 12 months, with a median duration of progression-free survival of 6 months. Four patients had progressive disease after 12 months. One patient stopped therapy after 2 weeks because of worsening of diarrhoea. Therapy was well tolerated, although transient mild-to-moderate nausea (n = 3), oedema (n = 3), diarrhoea (n = 2) and skin rash (n = 2) were observed.

CONCLUSION

Imatinib mesylate is well tolerated, no tumour remission was observed, only transient stable disease was achieved in some patients with advanced MTC.

New drugs in thyroid cancer

This review is focused on "new drugs" that might be developed for thyroid cancer treatment. Thyroid cancer is frequently associated to the activation of specific protein (RET, BRAF) and lipid [PI(3)K] kinases. There is good evidence that these genetic lesions are causative events in thyroid cancer initiation or progression. Therefore, novel compounds able to target these kinases might be useful for thyroid cancer treatment. The power of this approach is witnessed by the examples of BCR-ABL, c-KIT and EGFR inhibitors in the treatment of chronic myelogenous leukemia (CML), gastro-intestinal stromal tumors (GIST) and non-small cell lung carcinoma (NSCLC).

New therapeutic approaches for metastatic thyroid carcinoma

Treatment of metastatic differentiated thyroid cancer (DTC) includes the use of radioiodine and suppressive thyroid hormone treatment. A third of patients with distant metastases (who have radioiodine uptake, are younger than 40 years, have small metastases, and have well differentiated thyroid tumour) can be cured with radioiodine treatment. For other patients, there are no effective treatment modalities. However, the recent availability of molecularly targeted treatments has led to changes in the treatment strategy for DTC in patients with distant metastases, especially in those who are resistant to radioiodine treatment.