Endocrine tumours: progressive metastatic medullary thyroid carcinoma: first- and second-line strategies

Spontaneous and Treatment-Related Changes of Serum Calcitonin in Medullary Thyroid Cancer: Long-Term Experience in a Patient With Multiple Endocrine Neoplasia Type 2B

PURPOSE

Medullary thyroid carcinoma (MTC) in MEN2B syndrome is associated with germline RET mutation. Patients harboring de novo mutations are usually diagnosed at more advanced disease stages. We present a young woman with Met918Th mutation diagnosed with stage IV MTC at age 10 years.

METHODS

The disease progressed despite total thyroidectomy and multiple surgical interventions for cervical lymph node recurrences, leading to distant metastases in the fifth year after the initial diagnosis. Subsequently, she underwent five different types of tyrosine kinase inhibitor (TKI) treatments. The 17-year disease course was divided into periods defined by four surgical interventions and sequential treatment intervals with four multikinase (sunitinib, vandetanib, cabozantinib, and lenvatinib) and one RET-selective TKI (selpercatinib). Tumor growth for different phases of spontaneous development and drug treatment intervals was characterized by changes in serial log-transformed calcitonin measurements (n = 114).

RESULTS

Three operations (one for calcitonin-producing adrenal pheochromocytoma) were associated with drops in calcitonin levels. All of the nonselective TKIs were stopped due to adverse effects. As reflected by the negative calcitonin doubling rate, the best treatment response was observed with selpercatinib, which was associated with an initial large drop followed by a decreasing calcitonin trajectory over 514 days without any major side effects.

CONCLUSION

This case of MEN2B medullary thyroid cancer with long-term survival presents how the effectiveness of different treatment modalities can be estimated using log-transformed calcitonin levels. Furthermore, our experience supports the view that serial calcitonin measurements may be more sensitive than radiological follow-up in advanced MTC. Our patient also represents a new case of rarely reported calcitonin-producing pheochromocytomas.

Current perspectives on the management of patients with advanced RET-driven thyroid cancer in Europe

The incidence of thyroid cancer is increasing worldwide with the disease burden in Europe second only to that in Asia. In the last several decades, molecular pathways central to the pathogenesis of thyroid cancer have revealed a spectrum of targetable kinases/kinase receptors and oncogenic drivers characteristic of each histologic subtype, such as differentiated thyroid cancer, including papillary, follicular, and medullary thyroid cancer. Oncogenic alterations identified include B-Raf proto-oncogene (BRAF) fusions and mutations, neurotrophic tyrosine receptor kinase (NTRK) gene fusions, and rearranged during transfection (RET) receptor tyrosine kinase fusion and mutations. Multikinase inhibitors (MKIs) targeting RET in addition to multiple other kinases, such as sorafenib, lenvatinib and cabozantinib, have shown favourable activity in advanced radioiodine-refractory differentiated thyroid cancer or RET-altered medullary thyroid cancer; however, the clinical utility of MKI RET inhibition is limited by off-target toxicity resulting in high rates of dose reduction and drug discontinuation. Newer and selective RET inhibitors, selpercatinib and pralsetinib, have demonstrated potent efficacy and favourable toxicity profiles in clinical trials in the treatment of RET-driven advanced thyroid cancer and are now a therapeutic option in some clinical settings. Importantly, the optimal benefits of available specific targeted treatments for advanced RET-driven thyroid cancer require genetic testing. Prior to the initiation of systemic therapy, and in treatment-naïve patients, RET inhibitors may be offered as first-line therapy if a RET alteration is found, supported by a multidisciplinary team approach.

Metastatic medullary thyroid carcinoma (MTC): disease course, treatment modalities and factors predisposing for drug resistance

PURPOSE

MTC has varying clinical course. In cases with metastatic disease (meta-MTC) further therapeutic modalities (locoregional and/or Tyrosine-Kinase-Inhibitors, TKIs) are needed. Clinical features, disease progression, response to therapy and possible factors predisposing to TKIs response-resistance in meta-MTCs were investigated.

METHODS

Out of 338 MTC patients 54 had meta-MTC and were followed for 0.7-46 years (median 10.5); therapeutic interventions and response to therapy were recorded retrospectively.

RESULTS

Of 54 meta-MTC patients, 34/54 were men, 44/54 sporadic (age-at-diagnosis 47 ± 17.4 years, range: 5-78). Distant metastases at diagnosis were present in 12/54 (≥2 loci in 8/12), 7/12 received TKIs; During follow-up metastases occurred in 42/54 (within 0.6-25 years from diagnosis, median 5 yrs). Locoregional therapies were administered to 44/54 (81.5%) and TKIs to 40/54 (74.1%). Vandetanib was administered in 30 patients (24 as first-line therapy). The median progression-free-survival, PFS) was 48 months (range 4-120), partial response (PR): 26.7%, stable disease (SD): 23.3%, progressive disease (PD): 50.0%, cancer-specific survival: 44.8%, (16 in ongoing-therapy). More favorable disease course was recorded in familial-MTC compared to sporadic (p = 0.02) and in those patients with serious-adverse-events (SAEs) under treatment (p = 0.027). Those with biochemical progression under vandetanib, later showed more frequently structural progression (p = 0.007). Ten patients received cabozantinib (8/10 as second-line therapy, median PFS:11 months (3-36 months), 8/10 died). Three RET-mutant patients received selpercatinib; all showed PR. Within the total follow-up period, the response to therapy was: PR: 8/54 (14.8%), SD: 15/54 (27.8%), PD: 31/54 (57.4%), cancer-specific survival 46.3%. Mortality was higher in older patients (≥60 years) compared to younger ones (<60 yrs) (83.3 vs 45.2%, p = 0.021). Outcome was better in familial-MTC vs sporadic (PR: 50 vs 6.8%, SD: 20 vs 29.5%, PD: 30 vs 59.1%, p = 0.007).

CONCLUSIONS

Meta-MTCs treatment results in disease stabilization in 42.6% during a median 10.5 year follow-up. Combination of locoregional and systemic therapies may result in more favorable PFS. Family history, younger age, SAEs may predict better response; biochemical escape under TKI needs to be followed-up closely as it may indicate disease progression.

Total thyroidectomy vs thyroid lobectomy for localized medullary thyroid cancer in adults: A propensity-matched survival analysis

BACKGROUND

This study aimed to clarify whether the extent of thyroidectomy (total thyroidectomy vs thyroid lobectomy) influences survival in adults with localized medullary thyroid cancer.

METHODS

Patients with localized medullary thyroid cancer were identified using the Surveillance, Epidemiology, and End Results database (2000-2018). An independent cohort of patients with localized medullary thyroid cancer were retrospectively reviewed from three medical centers in China from 2010 to 2020. The patients were grouped by the extent of surgery (total thyroidectomy vs thyroid lobectomy). Primary end points were overall survival and disease-specific survival.

RESULTS

From 1,686 patients with medullary thyroid cancer identified in SEER, 1,122 patients met inclusion for matching, with a median follow-up of 99 months. After propensity score matching, 122 patients underwent a total thyroidectomy and 122 patients underwent a thyroid lobectomy. The 10-year overall survival was 85.2% (77.9%-90.7%) and 83.1% (75.5%-90.7%) in total thyroidectomy group and in thyroid lobectomy group, respectively. The 10-year disease-specific survival was 100% and 96.8% (93.1%-100%) in total thyroidectomy group and in thyroid lobectomy group, respectively. There was no statistically significant difference in overall survival or disease-specific survival in patients with localized medullary thyroid cancer undergoing total thyroidectomy or thyroid lobectomy (hazard ratio = 0.83, 95% confidence interval 0.44-1.57, P = .57 and hazard ratio = 0.49, 95% confidence interval 0.10-2.41, P = .39, respectively). Forty-seven patients with localized medullary thyroid cancer were identified in an independent Chinese cohort (n = 29 in total thyroidectomy group vs n = 18 in thyroid lobectomy group). After a median follow-up of 47 months, there was no mortality observed in either group.

CONCLUSION

This study suggests that the extent of thyroidectomy does not influence survival for patients with early-stage localized medullary thyroid cancer and that thyroid lobectomy might be adequate in this patient population.

Medullary thyroid cancer with ectopic Cushing's syndrome: A multicentre case series

OBJECTIVE

Ectopic Cushing's syndrome (ECS) induced by medullary thyroid cancer (MTC) is rare, and data on clinical characteristics, treatment and outcome are limited.

DESIGN

Retrospective cohort study in three German and one Swiss referral centres.

PATIENTS

Eleven patients with MTC and occurrence of ECS and 22 matched MTC patients without ECS were included.

MEASUREMENTS

The primary endpoint of this study was the overall survival (OS) in MTC patients with ECS versus 1:2 matched MTC patients without ECS.

RESULTS

The median age at diagnosis of ECS was 59 years (range: 35-81) and the median time between initial diagnosis of MTC and diagnosis of ECS was 29 months (range: 0-193). Median serum morning cortisol was 49 µg/dl (range: 17-141, normal range: 6.2-18). Eight (73%) patients received treatment for ECS. Treatment of ECS consisted of bilateral adrenalectomy (BADX) in four (36%) patients and adrenostatic treatment in eight (73%) patients. One patient received treatment with multityrosine kinase inhibitor (MKI) to control hypercortisolism. All patients experienced complete resolution of symptoms of Cushing's syndrome and biochemical control of hypercortisolism. Patients with ECS showed a shorter median OS of 87 months (95% confidence interval [95% CI]: 64-111) than matched controls (190 months, 95% CI: 95-285). Of the nine deaths, four were related to progressive disease (PD). Four patients showed PD as well as complications and comorbidities of hypercortisolism before death.

CONCLUSION

This study shows that ECS occurs in advanced stage MTC and is associated with a poor prognosis. Adrenostatic treatment and BADX were effective systemic treatment options in patients with MTC and ECS to control their hypercortisolism. MKI treatment achieved complete remission of hypercortisolism and sustained tumour control in one treated case.

State of the art and future directions in the systemic treatment of medullary thyroid cancer

PURPOSE OF REVIEW

Systemic treatment is the only therapeutic option for patients with progressive, metastatic medullary thyroid cancer (MTC). Since the discovery of the rearranged during transfection (RET) proto-oncogene (100% hereditary, 60-90% sporadic MTC), research has focused on finding effective systemic therapies to target this mutation. This review surveys recent findings.

RECENT FINDINGS

Multikinase inhibitors are systemic agents targeting angiogenesis, inhibiting growth of tumor cells and cells in the tumor environment and healthy endothelium. In the phase III EXAM and ZETA trials, cabozantinib and vandetanib showed progression-free survival benefit, without evidence of prolonged overall survival. Selpercatinib and pralsetinib are kinase inhibitors with high specificity for RET; phase I and II studies showed overall response rates of 73% and 71% in first line, and 69% and 60% in second line treatment, respectively. Although resistance mechanisms to mutation-driven therapy will be a challenge in the future, phase III studies are ongoing and neo-adjuvant therapy with selpercatinib is being studied.

SUMMARY

The development of selective RET-inhibitors has expanded the therapeutic arsenal to control tumor growth in progressive MTC, with fewer adverse effects than multikinase inhibitors. Future studies should confirm their effectiveness, study neo-adjuvant strategies, and tackle resistance to these inhibitors, ultimately to improve patient outcomes.

Ultrasonic Characteristics of Medullary Thyroid Carcinoma: Differential From Papillary Thyroid Carcinoma and Benign Thyroid Nodule

ABSTRACT

The aim of this study was to evaluate the differences in ultrasonic features of patients with medullary thyroid carcinoma (MTC), papillary thyroid carcinoma (PTC), and benign thyroid nodules. This study included 53 cases of MTC, 151 cases of PTC, and 200 cases of benign thyroid nodule which were pathologically confirmed. There were no significant differences in sex and thyroid gland involvement among the MTC, PTC, and benign thyroid nodule groups. The age among the 3 groups was statistically different (P = 0.002). The TNM stage of MTC was significantly higher than that of PTC (P < 0.001). Compared with PTC, the lesion size, shape, margin, echogenicity, internal nodule component, and blood flow were significantly different in MTC (P < 0.001, P < 0.001, P < 0.001, P < 0.001, P = 0.045, P < 0.001). However, there were no differences in the form of calcification and cervical lymph node involvement between the 2 groups (P = 0.671, P = 0.128). Except for the lesion size and shape (P = 0.068, P = 0.444), MTC group have significant differences in the grade of Thyroid Imaging Reporting and Data System, lesion margin, echogenicity, internal nodule component, calcification, cervical lymph node, and blood flow compared with benign thyroid nodule group (P < 0.001, P = 0.014, P = 0.032, P < 0.001, P < 0.001, P < 0.001). Our data indicate that ultrasound have important value in preoperative diagnosis of MTC. The ultrasonic features of MTC include relatively large nodules, aspect ratio less than 1, smooth edge, solid hypoechoic, microcalcification, and rich blood flow. It is necessary to combine multiple ultrasonic features for the differential diagnosis of MTC, PTC, and benign thyroid nodules.

Real-World Efficacy and Safety of Cabozantinib and Vandetanib in Advanced Medullary Thyroid Cancer

Background: Management of patients with advanced medullary thyroid cancer (MTC) remains a therapeutic challenge. The multi-tyrosine kinase inhibitors (TKIs) vandetanib and cabozantinib have been approved for the treatment of progressive MTC based on prolonged progression-free survival (PFS) in phase 3 clinical trials. Patients and Methods: To evaluate clinical characteristics, treatment regimens, efficacy, and treatment emergent adverse events (TEAEs) of vandetanib and cabozantinib in MTC patients outside clinical trials at four German tertiary care centers. Forty-eight patients diagnosed between 1990 and 2018 were included. PFS and overall survival (OS) probabilities were estimated using the Kaplan-Meier method and compared by log-rank test. Results: The median age at diagnosis was 46 years (15-80 years); a germ line RET (rearranged during transfection) mutation was known in 6 (13%) patients. Thirty-two (67%) patients showed progressive disease before TKI initiation. Forty-seven (98%) patients were treated with vandetanib and 23 (48%) patients with cabozantinib. Vandetanib was first-line treatment in 41 (85%) patients and cabozantinib in 7 (15%) patients. Partial response was the best response in 12 (26%) patients treated with vandetanib and in 5 (22%) patients treated with cabozantinib. Sixteen (34%) patients treated with vandetanib and 3 (13%) patients treated with cabozantinib had stable disease ≥24 weeks. The median PFS for vandetanib and cabozantinib was 17 months [95% confidence interval, CI, 9.3-24.6 months] and 4 months [CI 3.1-4.9 months], respectively. The 6- and 12-month survival rates were 98% and 86% for vandetanib and 78% and 70% for cabozantinib, respectively. The median OS for vandetanib and cabozantinib was 53 months [CI 43.7-62.3 months] and 24 months [CI 5.9-42.1 months], respectively. In vandetanib-treated patients, the PFS and OS were significantly longer in patients aged ≤60 years at TKI initiation and in patients with ≥5 TEAEs. Additionally, the PFS was longer in the absence of bone metastases. In cabozantinib-treated patients, the PFS was significantly longer in patients experiencing TEAEs and in patients aged ≤60 years, and the OS was significantly longer in patients who had TEAEs and in patients with ≥5 TEAEs. Conclusions: Vandetanib and cabozantinib are effective treatment options in the majority of MTC patients. We hypothesize that the poorer prognosis of cabozantinib-treated patients in our retrospective analysis is most likely due to its use as second-line treatment after treatment failure on vandetanib. However, different degrees of efficacy of the two drugs are possible.

Carcinoembryonic antigen should be concurrently checked with calcitonin to identify distant metastases in medullary thyroid cancer

Aim: This study investigates if serum calcitonin or carcinoembryonic antigen (CEA) levels can differentiate between locoregional and metastatic medullary thyroid cancer. Methods: A single institution retrospective analysis was performed on 88 patients with medullary thyroid cancer between 2008 and 2014. Results: In M0disease, calcitonin (p < 0.001) and CEA (p = 0.003) significantly decreased postoperatively. Not only was the correlation significant between calcitonin and CEA preoperatively (r = 0.72; p < 0.001) and postoperatively (r = 0.68; p < 0.001), calcitonin could extrapolate CEA levels (p < 0.001). These findings were statistically insignificant in metastatic disease. Conclusion: Independently, calcitonin and CEA fail to differentiate between locoregional and metastatic disease. Both are essential for prognostication: loss of concordance is suspicious for metastatic disease. Hence, discordant CEA and calcitonin levels should be an indication to pursue additional imaging.

Transcriptional targeting of oncogene addiction in medullary thyroid cancer

Metastatic medullary thyroid cancer (MTC) is incurable and FDA-approved kinase inhibitors that include oncogenic RET as a target do not result in complete responses. Association studies of human MTCs and murine models suggest that the CDK/RB pathway may be an alternative target. The objective of this study was to determine if CDKs represent therapeutic targets for MTC and to define mechanisms of activity. Using human MTC cells that are either sensitive or resistant to vandetanib, we demonstrate that palbociclib (CDK4/6 inhibitor) is not cytotoxic to MTC cells but that they are highly sensitive to dinaciclib (CDK1/2/5/9 inhibitor) accompanied by reduced CDK9 and RET protein and mRNA levels. CDK9 protein was highly expressed in 83 of 83 human MTCs and array-comparative genomic hybridization had copy number gain in 11 of 30 tumors. RNA sequencing demonstrated that RNA polymerase II-dependent transcription was markedly reduced by dinaciclib. The CDK7 inhibitor THZ1 also demonstrated high potency and reduced RET and CDK9 levels. ChIP-sequencing using H3K27Ac antibody identified a superenhancer in intron 1 of RET. Finally, combined inhibition of dinaciclib with a RET kinase inhibitor was synergistic. In summary, we have identified what we believe is a novel mechanism of RET transcription regulation that potentially can be exploited to improve RET therapeutic targeting.

Reduced Retinoblastoma Protein Expression Is Associated with Decreased Patient Survival in Medullary Thyroid Cancer

BACKGROUND

The retinoblastoma (RB) transcriptional corepressor 1 protein functions to slow cell-cycle progression. Inactivation of RB by reduced expression and/or hyperphosphorylation allow for enhanced progression through the cell cycle. Murine models develop medullary thyroid carcinoma (MTC) after generalized loss of RB. However, RB expression in MTC has only been evaluated in a small number of tumors, with differing results. The objective of this study was to determine whether reduced expression of RB and/or overexpression of hyperphosphorylated RB predict MTC aggressive behavior.

METHODS

Formalin-fixed, paraffin-embedded primary thyroid tumors and lymph node metastases from MTC patients were evaluated for calcitonin, RB, and phosphorylated RB (pRB) expression by immunohistochemistry. Two expert pathologists evaluated the slides in a blinded manner, and the immunohistochemistry results were compared to disease-specific survival as a primary endpoint.

RESULTS

Seventy-four MTC samples from 56 patients were analyzed in this study, including 51 primary tumors and 23 lymph node metastases. The median follow-up time was 6.75 years after surgery (range 0.64-24.30 years), and the median primary tumor size was 30 mm (range 6-96 mm). Sixty-six percent of cases were classified as stage IV. RB nuclear expression was diffusely present in 88% of primary tumors and 78% of lymph node metastases. Nuclear pRB expression was present in 22% of primary tumors and 22% of lymph node metastases. On univariate analysis, reduced RB (<75% tumor cell staining) trended with lower MTC-specific survival for primary tumor and metastatic nodes (primary tumor hazard ratio = 3.54 [confidence interval 0.81-15.47], p = 0.08; and lymph node hazard ratio = 4.35 [confidence interval 0.87-21.83], p = 0.05). For primary tumors, multivariable analysis showed that low nuclear RB expression was independently associated with worse disease-specific (p = 0.01) and overall (p = 0.02) survival. pRB levels were not associated with survival for either primary tumor or lymph node metastases.

CONCLUSIONS

Reduced RB expression is associated with decreased patient survival in univariate and multivariable analyses, independent from patient age at surgery or advanced TNM stage. Future studies involving larger MTC patient populations are warranted to determine if lower RB expression levels may serve as a biomarker for aggressive disease in patients with MTC.

CXCR4/CXCR7/CXCL12 axis promotes an invasive phenotype in medullary thyroid carcinoma

Background:

Medullary thyroid carcinoma (MTC) is a rare and challenging endocrine malignancy. Once spread, the therapeutic options are limited and the outcome poor. For these patients, the identification of new druggable biological markers is of great importance. Here, we investigated the prognostic and biological role of the C-X-C chemokine receptors type 4 and 7 (CXCR4/7) in MTC.

Methods:

Eighty-six MTC and corresponding non-neoplastic thyroid specimens were immunohistochemically stained for CXCR4/7 using tissue microarray technology and expression levels correlated with clinicopathological variables. Medullary thyroid carcinoma cell line TT was treated with recombinant human SDF1α/CXCL12 (rh-SDF1α) and CXCR4 antagonists AMD3100 and WZ811. Changes in cell cycle activation, tumour cell invasiveness as well as changes in mRNA expression levels of genes associated with epithelial–mesenchymal transition (EMT) were investigated.

Results:

High CXCR4 expression was associated with large tumour size and metastatic disease. CXCR4 antagonists significantly reduced tumour cell invasiveness, while the treatment with rh-SDF1α stimulated invasive growth, caused cell cycle activation and induced EMT.

Conclusions:

The CXCR4/CXCR7/CXCL12 axis plays an important role in MTC. We provide first evidence that the chemokine receptors might serve as potential therapeutic targets in patients with advanced MTC and offer new valuable insight into the underlying molecular machinery of metastatic MTC.

Overall survival analysis of EXAM, a phase III trial of cabozantinib in patients with radiographically progressive medullary thyroid carcinoma

BACKGROUND

Primary analysis of the double-blind, phase III Efficacy of XL184 (Cabozantinib) in Advanced Medullary Thyroid Cancer (EXAM) trial demonstrated significant improvement in progression-free survival with cabozantinib versus placebo in patients with progressive medullary thyroid cancer (MTC). Final analysis of overall survival (OS), a key secondary endpoint, was carried out after long-term follow-up.

PATIENTS AND METHODS

EXAM compared cabozantinib with placebo in 330 patients with documented radiographic progression of metastatic MTC. Patients were randomized (2:1) to cabozantinib (140 mg/day) or placebo. Final OS and updated safety data are reported.

RESULTS

Minimum follow-up was 42 months. Kaplan-Meier analysis showed a 5.5-month increase in median OS with cabozantinib versus placebo (26.6 versus 21.1 months) although the difference did not reach statistical significance [stratified hazard ratio (HR), 0.85; 95% confidence interval (CI), 0.64-1.12; P = 0.24]. In an exploratory assessment of OS, progression-free survival, and objective response rate, cabozantinib appeared to have a larger treatment effect in patients with RET M918T mutation-positive tumors compared with patients not harboring this mutation. For patients with RET M918T-positive disease, median OS was 44.3 months for cabozantinib versus 18.9 months for placebo [HR, 0.60; 95% CI, 0.38-0.94; P = 0.03 (not adjusted for multiple subgroup analyses)], with corresponding values of 20.2 versus 21.5 months (HR, 1.12; 95% CI, 0.70-1.82; P = 0.63) in the RET M918T-negative subgroup. Median treatment duration was 10.8 months with cabozantinib and 3.4 months with placebo. The safety profile for cabozantinib remained consistent with that of the primary analysis.

CONCLUSION

The secondary end point was not met in this final OS analysis from the trial of cabozantinib in patients with metastatic, radiographically progressive MTC. A statistically nonsignificant increase in OS was observed for cabozantinib compared with placebo. Exploratory analyses suggest that patients with RET M918T-positive tumors may experience a greater treatment benefit with cabozantinib.

TRIAL REGISTRATION NUMBER

NCT00704730.

Systemic treatment and management approaches for medullary thyroid cancer

Although rare, medullary thyroid cancer (MTC) exemplifies the value that ever-expanding knowledge of molecular pathways and mechanisms brings to managing challenging cancers. Although surgery can be curative for MTC in many patients, a substantial proportion of patients present with locoregional or distant metastatic disease. Once distant disease occurs, treatment options are limited, and conventional cancer treatments such as cytotoxic chemotherapy are of minimal benefit. Biomarkers such as calcitonin and carcinoembryonic antigen are important correlates of disease burden as well as predictors of disease progress, including recurrence and survival. MTC is either sporadic (∼75%) or inherited (∼25%) as an autosomal dominant disease. Regardless, germline and somatic mutations, particularly in the rearranged during transfection (RET) proto-oncogene, are key factors in the neoplastic process. Gain-of-function RET mutations result in overactive proteins that lead to abnormal activation of downstream signal transduction pathways, resulting in ligand-independent growth and resistance to apoptotic stimuli. Specific RET mutation variants have been found to correlate with phenotype and natural history of MTC with some defects portending a more aggressive clinical course. Greater understanding of the consequence of the aberrant signaling pathway has fostered the development of targeted therapies. Two small-molecule tyrosine kinase inhibitors, vandetanib and cabozantinib, are currently available as approved agents for the treatment of advanced or progressive MTC and provide significant increases in progression-free survival. Since there have been no head-to-head comparisons, clinicians often select between these agents on the basis of familiarity, patient characteristics, comorbidities, and toxicity profile.

Management of hereditary medullary thyroid carcinoma

Hereditary medullary thyroid carcinoma (MTC) represents up to one-third of MTC cases and includes multiple endocrine neoplasia syndrome type 2A (and its variant familial MTC) and 2B. The aim of this paper is to provide an overview of the disease focusing on the management of hereditary MTC patients, who have already developed tumor, as well as discuss the recommended approach for asymptomatic family members carrying the same mutation. A PubMed search was performed to review recent literature on diagnosis, genetic testing, and surgical and medical management of hereditary MTC. The wide use of genetic testing for RET mutations has markedly influenced the course of hereditary MTC. Prophylactic thyroidectomy of RET carriers at an early age eliminates the risk of developing MTC later in life. Pre-operative staging is a strong prognostic factor in patients, who have developed MTC. The use of recently approved tyrosine kinase inhibitors (vandetanib, cabozantinib) holds promising results for the treatment of unresectable, locally advanced, and progressive metastatic MTC. Genetic testing of the RET gene is a powerful tool in the diagnosis and prognosis of MTC. Ongoing research is expected to add novel treatment options for patients with advanced, progressive disease.

Selective use of vandetanib in the treatment of thyroid cancer

Vandetanib is a once-daily orally available tyrosine kinase inhibitor that works by blocking RET (REarranged during Transfection), vascular endothelial growth factor receptor (VEGFR-2, VEGFR-3), and epidermal growth factor receptor and to a lesser extent VEGFR-1, which are important targets in thyroid cancer (TC). It is emerging as a potentially effective option in the treatment of advanced medullary thyroid cancer (MTC) and in dedifferentiated papillary thyroid cancer not responsive to radioiodine. The most important effect of vandetanib in aggressive MTC is a prolongation of progression-free survival and a stabilization of the disease. Significant side effects have been observed with the vandetanib therapy (as fatigue, hypertension, QTc prolongation, cutaneous rash, hand-and-foot syndrome, diarrhea, etc), and severe side effects can require the suspension of the drug. Several studies are currently under way to evaluate the long-term efficacy and tolerability of vandetanib in MTC and in dedifferentiated papillary TC. The efficacy of vandetanib in patients with MTC in long-term treatments could be overcome by the resistance to the drug. However, the effectiveness of the treatment could be ameliorated by the molecular characterization of the tumor and by the possibility to test the sensitivity of primary TC cells from each subject to different tyrosine kinase inhibitor. Association studies are evaluating the effect of the association of vandetanib with other antineoplastic agents (such as irinotecan, bortezomib, etc). Further research is needed to determine the ideal therapy to obtain the best response in terms of survival and quality of life.