Search

This document is a letter to the editor of the journal Thyroid discussing the prevalence of erectile dysfunction (ED) in patients with RET-altered thyroid cancer who are treated with selpercatinib. The authors conducted a retrospective cohort study of 25 male patients and found that 92% of them reported ED. The study suggests that ED may be a common side effect of selpercatinib treatment and that phosphodiesterase-5 inhibitors (PDE-5i) may be effective in managing this adverse event. Further research is needed to confirm these findings and explore optimal management strategies. The authors acknowledge the support of Eli Lilly and Company in reviewing the study. [Extracted from the article]

RET somatic mutation analysis in sporadic MTC should be guided by postoperative evaluation results. [ABSTRACT FROM AUTHOR]

Somatic copy number alterations (SCNA) involving either a whole chromosome or just one of the arms, or even smaller parts, have been described in about 88% of human tumors. This study investigated the SCNA profile in 40 well-characterized sporadic medullary thyroid carcinomas by comparative genomic hybridization array. We found that 26/40 (65%) cases had at least one SCNA. The prevalence of SCNA, and in particular of chromosome 3 and 10, was significantly higher in cases with a RET somatic mutation. Similarly, SCNA of chromosomes 3, 9, 10 and 16 were more frequent in cases with a worse outcome and an advanced disease. By the pathway enrichment analysis, we found a mutually exclusive distribution of biological pathways in metastatic, biochemically persistent and cured patients. In particular, we found gain of regions involved in the intracellular signaling and loss of regions involved in DNA repair and TP53 pathways in the group of metastatic patients. Gain of regions involved in the cell cycle and senescence were observed in patients with biochemical disease. Finally, gain of regions associated with the immune system and loss of regions involved in the apoptosis pathway were observed in cured patients suggesting a role of specific SCNA and corresponding altered pathways in the outcome of sporadic MTC. [ABSTRACT FROM AUTHOR]

Context: The clinical response after surgery is a determinant in the management of patients with medullary thyroid carcinoma (MTC). In case of excellent or structural incomplete response, the follow-up strategies are well designed. Conversely, in case of biochemical incomplete response (BiR) the management is not clearly defined. Objective: This work aimed to evaluate the overall and per-site prevalence of structural disease detection in sporadic MTC patients with BiR and to assess the predictive value of various clinical, biochemical, and genetic features. Methods: We evaluated data of 599 consecutive patients surgically treated for sporadic MTC (2000-2018) and followed-up at the endocrine unit of the University Hospital of Pisa. Results: After a median of 5 months from surgery, 145 of 599 (24.2%) patients were classified as BiR. Structural disease was detected in 64 of 145 (44.1%), after a median time of 3.3 years. In 73.6%, structural disease was detected at a single site, prevalently cervical lymph nodes. Among several others, at the time of first evaluation after surgery, only basal calcitonin (bCTN) and stage IVa/b were independent predictive factors. Also, structural disease was more frequent in patients with shorter CTN doubling time and somatic RET mutation. Conclusion: In sporadic MTC patients with BiR, the risk of detection of structural disease was about 50% at 10 years. Higher bCTN levels and staging predicted the risk of detecting structural disease. According to these findings, stricter follow-up should be reserved for MTC with BiR and elevated values of bCTN and to those with an advanced stage. Long follow-up should be considered for all BiR patients since 50% of them develop structural disease within 10 years. [ABSTRACT FROM AUTHOR]

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 offtarget 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. [ABSTRACT FROM AUTHOR]

Objective: About 20% of sporadic medullary thyroid carcinomas (MTC) have no RET/RAS somatic alterations or other known gene alterations. The aim of this study was to investigate RET/RAS-negative MTC for the presence of NF1 alterations. Methods: We studied 18 sporadic RET/RAS-negative MTC cases. Next-generation sequencing (NGS) of tumoral and blood DNA was performed using a custom panel including the entire coding region of the NF1 gene. The effect of NF1 alterations on the transcripts was characterized by reverse transcriptase-polymerase chain reaction (RT-PCR), and the loss of heterozygosity (LOH) of the other NF1 allele was investigated with Multiplex Ligation-dependent Probe Amplification (MLPA). Results: Two cases showed biallelic inactivation of NF1 with a prevalence of about 11% of RET/RAS-negative cases. In a patient affected by neurofibromatosis, there was a somatic intronic point mutation determining the transcript alteration in 1 allele and a germline LOH in the other. In a second patient, we described that both the point mutation and the LOH were somatic events; this latter finding shows, for the first time, a driver role of NF1 inactivation in MTC independent of RET/RAS alterations and the presence of neurofibromatosis. Conclusions: About 11% of our series of sporadic RET/RAS-negative MTC harbor biallelic inactivation of the NF1 suppressor gene also regardless of neurofibromatosis status. According to our results, NF1 alterations should be searched in all RET/RAS-negative MTC as possible drivers. Moreover, this finding reduces the number of negative sporadic MTC and may have important clinical implications in the management of these tumors. [ABSTRACT FROM AUTHOR]

Context: Although the majority of RET alterations are single nucleotide variants (SNV), small deletions and/or insertions have been reported at variable prevalence. No information about the efficacy of RET-specific inhibitors in patients harboring RET indels has been provided. Objective: We present an update on the prevalence of RET indels in medullary thyroid cancer (MTC) and describe the efficacy of selpercatinib in patients with advanced MTC with RET indels. Methods: The MTC tissues of 287 patients were analyzed using an Ion S5 targeted sequencing. The functional role of the reported indels have been evaluated by MutationTaster. Clinical and pathological data of MTC patients harboring a RET indel were collected and analyzed. Two patients with a RET indel were treated with selpercatinib. Results: Among 178 RET-positive cases, 147 (82.6%) harbored a SNV and 31 (17.4%) a RET in-frame indel. Nine indels were not previously reported and were found to be disease causing by MutationTaster. Patients harboring an indel were found to have an aggressive disease and 2 of them were treated with selpercatinib, experiencing a good response to the treatment. Conclusion: These data show that RET indels are not infrequent and correlate with an aggressive disease. Two RET indel–positive patients showed a partial response to the treatment with a highly selective RET inhibitor; thus, these RET indels can be considered actionable mutations. In order to not miss these alterations, the analysis of the full gene is recommended. [ABSTRACT FROM AUTHOR]

Context: Measurement of driver mutations in circulating tumoral DNA (ctDNA) obtained by liquid biopsy has been shown to be a sensitive biomarker in several human tumors. Objective: The aim of this study was to evaluate the clinical relevance of pre- and post-operative ctDNA in sporadic medullary thyroid cancer (sMTC). Methods: We studied pre- and post-operative ctDNA in 26 and 23 sMTC patients, respectively. ctDNA results were correlated to serum calcitonin (Ct), carcinoembryonic antigen (CEA), and other clinical/pathological features. Results: Twenty-six of 29 (89.7%) sMTCs were mutated either for RET or RAS and 3/29 (10.3%) were negative. Four of 26 (15.4%) cases showed positive pre-operative ctDNA with a significantly higher presence of RET M918T mutation (P = 0.0468). Patients with positive preoperative ctDNA showed a higher variation allele frequency value of the somatic driver mutation (P = 0.0434) and a higher frequency of persistent disease (P = 0.0221). Post-operative ctDNA was positive only in 3/23 (13%) sMTCs and no one was positive for pre-operative ctDNA. Higher values of both Ct (P = 0.0307) and CEA (P = 0.0013) were found in positive ctDNA cases. Finally, the 7 cases harboring either pre- or post-operative positive ctDNA had a persistent disease (P = 0.0005) showing a higher post-operative serum Ct when compared with cases with negative ctDNA (P = 0.0092). Conclusions: Pre-operative ctDNA in medullary thyroid cancer is not useful for diagnostic purposes, but it can be useful for predicting the outcome of the disease. In our series, post-operative ctDNA showed a potential for monitoring the response to therapies, but further studies are required to confirm our results. [ABSTRACT FROM AUTHOR]

Medullary thyroid carcinoma (MTC) is a neuroendocrine malignant tumor originating from parafollicular C-cells producing calcitonin. Most of cases (75%) are sporadic while the remaining (25%) are hereditary. In these latter cases medullary thyroid carcinoma can be associated (multiple endocrine neoplasia type IIA and IIB) or not (familial medullary thyroid carcinoma), with other endocrine diseases such as pheochromocytoma and/or hyperparathyroidism. RET gene point mutation is the main molecular alteration involved in MTC tumorigenesis, both in sporadic and in hereditary cases. Total thyroidectomy with prophylactic/therapeutic central compartment lymph nodes dissection is the initial treatment of choice. Further treatments are needed according to tumor burden and rate of progression. Surgical treatments and local therapies are advocated in the case of single or few local or distant metastasis and slow rate of progression. Conversely, systemic treatments should be initiated in cases with large metastatic and rapidly progressive disease. In this review, we discuss the details of systemic treatments in advanced and metastatic sporadic MTC, focusing on multikinase inhibitors, both those already used in clinical practice and under investigation, and on emerging treatments such as highly selective RET inhibitors and radionuclide therapy. [ABSTRACT FROM AUTHOR]

Objective: Recently, several scientific societies designed ultrasound (US) risk stratification systems (RSS) to guide the workup of thyroid nodules and decide which nodules should under go fine-needle aspiration cytology (FNAC). However, these systems have been developed against papillary thyroid car cinoma, and scanty data on their role in identifying medullary thyroid carcinoma (MTC) are available. The aims of this study are to describe the US features of MTC and evaluate the performance of RSS in identifying MTC. Methods: Data of 152 consecutive patients with MTC was evaluated. The re sults of the pre-operative neck US of all patients were collected. Ultrasound features of each MTC were e valuated and classified according to the five main RSS available. Results: Median MTC dimension was 1.3 cm. Most of the nodules showed so lid composition, hypoechoic pattern, and regular margins. About half of them showed the presence of calcifications, but only a subgroup had microcalcifications. A minority of the nodules showed a 'taller than wide' shape. Only 7.9% of all MTC showed the simultaneous presence of at least four US features suggestive of malignancy. Ultrasonographic high-risk of malignancy of the MTC included in the five RSS, varied from 45.4 to 47.4%, and performing FNAC was suggested in only 48.7 to 63.8% of all MTC. Conclusions: In this series, neither single nor the association of US featu res are specific for MTC. The five main RSS correctly identify less than 50% of MTC and do not suggest perf orming FNAC in about half of them with potentially missed or delayed diagnosis. [ABSTRACT FROM AUTHOR]

Background: Serum Ca19.9 positivity is a prognostic factor for mortality in patients with advanced medullary thyroid cancer (aMTC), independently from calcitonin doubling time (DT). However, it is unknown whether aMTC patients who become positive for Ca19.9 also have progressive disease (PD) according to response evaluation criteria in solid tumors (RECIST) and whether Ca19.9 DT has a role in the management of aMTC patients. The aims of this study were to evaluate whether in aMTC, when serum Ca19.9 becomes positive, PD develops, and to determine the role of Ca19.9 DT in predicting mortality and PD. Patients and Methods: Serum Ca19.9 was periodically measured in 107 aMTC patients, and the DTs were calculated. Restaging of the disease was radiologically performed in 104 of 107 patients and PD was evaluated according to RECIST. Results: At the end of follow-up, 25 of 107 patients were Ca19.9 positive and PD was identified in 30 of 104 patients. No significant association was found between Ca19.9 positivity and PD, while there was a significant association between Ca19.9 positivity and mortality (p < 0.0001). Ca19.9 DTs <6 months and <1 year were not associated with PD but were associated with mortality (p < 0.0001 and p < 0.0001, respectively). In particular, 3 patients who had a Ca19.9 DT <6 months with no evidence of PD according to RECIST died of their disease after 6, 5, and 3 months, respectively. Conclusions: Serum Ca19.9 positivity and DTs <6 months and <1 year are prognostic factors for mortality but not for PD. Serum Ca19.9 positivity and DTs <6 months and <1 year should be considered in the decision-making process of whether to initiate systemic therapy even if there is no evidence of PD according to RECIST. [ABSTRACT FROM AUTHOR]

Background: Sporadic medullary thyroid carcinoma (sMTC) is an uncommon neoplasia arising from the calcitonin-producing parafollicular cells of the thyroid. Previous studies evaluated whether single nucleotide polymorphisms (SNPs) within RET (a pivotal proto-oncogene for this disease) are associated with the risk for developing sMTC, but the results are inconclusive. Methods: In this work, we evaluated the association of RET-SNPs c.74-126G>T (rs2565206), p.Gly691Ser (rs1799939, G>A), p.Leu769 = (rs1800861, G>T), p.Ser836 = (rs1800862, C>T), and p.Ser904 = (rs1800863, C>G) (listed in the order of their chromosomal location) with sMTC. This is one of the largest case–control association studies carried out on sMTC, including 585 sMTC cases (negative for germline mutations within RET), 1529 patients affected by sporadic nonmedullary thyroid carcinoma (sNMTC), and 989 healthy controls, from central and southern Italy and collected in the period 2000–2017. Results: sNMTC patients showed similar genotype and allele frequencies compared with healthy controls. On the other hand, among sMTC patients, the T-allele of p.Leu769 = was less frequent (OR = 0.70 [CI 0.58–0.84], p = 1.9 × 10−4) and rare homozygotes TT showed an OR = 0.32 ([CI 0.17–0.60], p = 2.3 × 10−4). Moreover, a statistically significant excess of the haplotype 2 (characterized by the alleles T-G-G-C-C of the listed SNPs) was observed (p = 3.9 × 10−3). The SNPs were not associated with the expression of RET mRNA, that is, they did not exert an effect in cis as quantitative trait locus (cis-eQTL). However, a strong eQTL association was found for p.Leu769 = and the neighboring gene CSGALNACT2 (p = 9.3 × 10−50; effect-size = −0.65), whose function in cancer is unknown. Conclusions: This study shows that specific RET haplotypes, in particular haplotype 2 and the T-allele of p.Leu769 = , are associated with a reduced risk of sMTC in Italians. [ABSTRACT FROM AUTHOR]

Background. Multiple endocrine neoplasia type 2 (MEN2) is a hereditary cancer syndrome caused by RET proto-oncogene mutation. Two different clinical variants of MEN2 are known (MEN2A and MEN2B): medullary thyroid carcinoma (MTC) almost always present and associated with pheochromocytoma (Pheo), and primary hyperparathyroidism (HPTH) in MEN2A and with Pheo and other nonendocrine diseases in MEN2B. Case Report. A 7-year-old girl, previously treated for a pelvic plexiform neurofibroma, arrived at our observation with a peculiar MEN2B syndrome and with HPTH. The neck ultrasound showed bilateral thyroid nodules, local lymph node lesions, and a suspicious left hyperplastic parathyroid. The CT scan showed a megacolon and described the persistence of the pelvic tumor. A new RET germline deletion in exon 11 (c.1892_1899delCGAGCT; p.Glu632_Leu633del) was found. She underwent total thyroidectomy, central compartment and latero-cervical lymph node dissection, and neck exploration for primary HPTH. The histology confirmed bilateral MTC, multiple lymph node metastases, a hyperplastic parathyroid, and a parathyroid adenoma. Conclusions. This is the first case of a complex syndrome characterized by peculiar features of MEN2B, without Pheo but with a pelvic plexiform neurofibroma and with HPTH, which is typical of MEN2A. A "de novo" new germline RET deletion located in exon 11 was found. [ABSTRACT FROM AUTHOR]

Vandetanib is an oral tyrosine kinase inhibitor approved for treatment of advanced symptomatic or progressive medullary thyroid cancer (MTC). The current study (NCT01496313) evaluated the benefit-risk of two starting doses of vandetanib in patients with symptomatic or progressive MTC. Patients were randomized 1:1 to receive vandetanib 150 or 300 mg daily and followed for a maximum of 14 months (Part A), with the option to then enter an open-label phase (Part B) inve stigating vandetanib 100, 150, 200 and 300 mg daily doses. Efficacy was assessed in Pa rt A, and safety and tolerability during Parts A and B up to 2 years post randomizat ion. Eighty-one patients were randomized in Part A and 61 patients entered Part B, of wh om 37 (60.7%) received 2 years of treatment. Overall, 25% of patients experienced an objective response (OR) at 14 months (OR rate, 0.29 (95% CI, 0.176-0.445) for 300 mg, and 0.20 (95% CI, 0.105-0.348) for 150 mg; one-sided P value approximately 0.43). The most common adverse events (AEs) included diarrhea, hypocalcemia, asthenia, QTc prolongation, hypokalemia and keratopathy, all at generally higher incidence with 300 vs 150 mg (Part A). Part B safety and tolerability was consistent with Part A. OR was observed wi th both vandetanib doses; the 300 mg dose showed a more favorable trend vs 150 mg as init ial dose. Thus, for most patients, 300 mg vandetanib is the most appropriate starting dose; dose reductions to manage AEs and lower initial doses for patients with particular comorbidities can be considered. [ABSTRACT FROM AUTHOR]

Background: Cabozantinib significantly prolonged progression-free survival (PFS) versus a placebo in patients with progressive, metastatic medullary thyroid cancer (MTC; P < .001). An exploratory analysis of phase 3 trial data evaluated the influence of rearranged during transfection (RET) and RAS (HRAS, KRAS, and NRAS) mutations on cabozantinib clinical activity.Methods: Patients (n = 330) were randomized to cabozantinib (140 mg/day) or a placebo. The primary endpoint was PFS. Additional outcome measures included PFS, objective response rates (ORRs), and adverse events in RET and RAS mutation subgroups.Results: Among all study patients, 51.2% were RET mutation-positive (38.2% with RET M918T), 34.8% were RET mutation-unknown, and 13.9% were RET mutation-negative. Sixteen patients were RAS mutation-positive. Cabozantinib appeared to prolong PFS versus the placebo in the RET mutation-positive subgroup (hazard ratio [HR], 0.23; 95% confidence interval [CI], 0.14-0.38; P < .0001), the RET mutation-unknown subgroup (HR, 0.30; 95% CI, 0.16-0.57; P = .0001), and the RAS mutation-positive subgroup (HR, 0.15; 95% CI, 0.02-1.10; P = .0317). The RET M918T subgroup achieved the greatest observed PFS benefit from cabozantinib versus the placebo (HR, 0.15; 95% CI, 0.08-0.28; P < .0001). The ORRs for RET mutation-positive, RET mutation-negative, and RAS mutation-positive patients were 32%, 22%, and 31%, respectively. No PFS benefit was observed in patients lacking both RET and RAS mutations, although the ORR was 21%. The safety profile for all subgroups was similar to that for the overall cabozantinib arm.Conclusions: These data suggest that cabozantinib provides the greatest clinical benefit to patients with MTC who have RET M918T or RAS mutations. However, a prospective trial is needed to confirm the relation between genetic variation and the response to cabozantinib. Cancer 2016;122:3856-3864. © 2016 American Cancer Society. [ABSTRACT FROM AUTHOR]

Background: Medullary thyroid cancer (MTC) is capable of secreting several proteins, such as calcitonin (Ct), carcinoembryonic antigen (CEA), chromogranin and others. Recently, we observed an aggressive MTC with high levels of serum carbohydrate antigen 19.9 (Ca 19.9) and a rapid evolution to death. Objective: The aim of this study was to evaluate whether high levels of serum Ca 19.9 could be a prognostic factor of death in patients with advanced MTC. Patients and methods: We measured Ca 19.9, CEA and Ct in 100 advanced structural recurrent/persistent MTC patients and in 100 cured or biochemically affected MTC patients. Clinical and pathological data were also collected. Results: Sixteen percent of the patients with advanced MTC had high levels of Ca 19.9. The group with abnormal Ca 19.9 levels had significantly higher levels of CEA and Ct compared with the group with normal values of Ca 19.9 (P<0.0001 for both Ct and CEA). At variance, all 100 patients in the MTC control group showed normal levels of Ca 19.9. Moreover, among the advanced cases, the Ca 19.9-positive group showed a higher mortality rate than the group with normal levels. A logistic regression analysis demonstrated that an elevated level of Ca 19.9 is a predictor of mortality (OR=3.78, P=0.04), independent from Ct doubling time. Conclusions: These results demonstrated that an elevated value of serum Ca 19.9 appears to be a predictive factor of poor prognosis in advanced MTC patients and identifies those cases with a higher risk of mortality in the short term. [ABSTRACT FROM AUTHOR]

Introduction: The American Thyroid Association appointed a Task Force of experts to revise the original Medullary Thyroid Carcinoma: Management Guidelines of the American Thyroid Association. Methods: The Task Force identified relevant articles using a systematic PubMed search, supplemented with additional published materials, and then created evidence-based recommendations, which were set in categories using criteria adapted from the United States Preventive Services Task Force Agency for Healthcare Research and Quality. The original guidelines provided abundant source material and an excellent organizational structure that served as the basis for the current revised document. Results: The revised guidelines are focused primarily on the diagnosis and treatment of patients with sporadic medullary thyroid carcinoma (MTC) and hereditary MTC. Conclusions: The Task Force developed 67 evidence-based recommendations to assist clinicians in the care of patients with MTC. The Task Force considers the recommendations to represent current, rational, and optimal medical practice. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: Hereditary medullary thyroid carcinoma (MTC) therapy is surgical resection. Because the genetic screening was available, the early diagnosis of the disease has been possible. The purpose of this study was to evaluate the role of the genetic test in the management of these children and to draw some information about the surgical timing. Methods: Thirteen patients underwent total thyroidectomy at our institute between 1995 and 2007. Seven patients underwent a curative thyroidectomy, and 6 patients underwent a prophylactic thyroidectomy. Two patients were operated with a minimally invasive video-assisted technique. We studied the following parameters: age, risk level associated to the RET gene mutations, aim of surgery (curative or prophylactic), tumor histopathologic features, lymph node involvement, and distal metastases. Results: We found a statistical association between cancer maximum diameter and some parameters analyzed: age of patients, aim of surgery, single or multifocal MTC, and number of organs involved by distal metastases. Cancer diameter at the moment of diagnosis seems to increase according to the aggressiveness of RET gene mutation found. Conclusions: The best strategy to cure MTC is to prevent it. Genetic screening could be a fundamental tool in the management of multiple endocrine neoplasm type 2 children. An improvement of scientific knowledge regarding RET gene alterations and an early and appropriate use of genetic tests could allow a better understanding of the correct surgical timing and a wider use of less aggressive surgical procedures. [ABSTRACT FROM AUTHOR]

Calcitonin (CT) is secreted mainly by parafollicular C cells. In normal subjects, serum CT (sCT) levels are low and barely detectable by commonly used assays. Increased sCT levels are highly suggestive of medullary thyroid carcinoma (MTC). Since the clinical manifestation of MTC is a thyroid nodule, either single or in the context of a multinodular goitre, the routine measurement of sCT in the evaluation of thyroid nodule(s) facilitates the diagnosis of MTC. sCT measurement is indeed more sensitive than cytology in finding MTC. There are two major benefits from this clinical practice: (a) the surgeon is alerted to the need to perform total thyroidectomy and central compartment lymphadenectomy, which is the minimal surgical treatment for MTC; and (b) the outcome of MTC is favourably affected because it is usually identified at a less advanced stage. However, other non-MTC causes of hypercalcitoninaemia and false sCT positivity do exist and must be recognized. The differential diagnosis is possible using previously validated assays against possible sources of interference, and performing stimulation tests with pentagastrin or, eventually, calcium infusion. [Copyright &y& Elsevier]

This study was designed to investigate whether RET (rearranged during transfection) mRNA over-expression could be considered an alternative driver event for the development of medullary thyroid carcinoma (MTC), and if different RET isoforms could play a role in MTC tumorigenesis. Eighty-three MTC patients, whose mutational profile was previously identified by next-generation sequencing (NGS) IONS5, were included in this study. Expression analysis was performed by the quantitative reverse transcription-polymerase chain reaction technique. RET expression levels were found to be significantly higher in cases with RET somatic mutations than in cases that were negative for RET somatic mutations (p = 0.003) as well as in cases with a somatic mutation, either in RET or RAS than in cases negative for both these mutations (p = 0.01). All cases were positive for the RET51 isoform expression while only 72/83 (86.7%) were positive for RET9 isoform expression. A statistically significant higher expression of the RET51 isoform was found in cases positive for RET somatic mutation than in cases either positive for RAS mutation (p = 0.0006) or negative for both mutations (p = 0.001). According to our data, RET gene over-expression does not play a role in MTC tumorigenesis, neither as an entire gene or as an isoform. At variance, the RET gene, and in particular the RET51 isoform, is expressed higher in RET mutated cases. On the basis of these results we can hypothesize that the overexpression of RET, and in particular of RET51, could potentiate the transforming activity of mutated RET, making these cases more aggressive. [ABSTRACT FROM AUTHOR]

Thyroid carcinoma is the most frequent endocrine neoplasia. Different types of thyroid carcinoma are described: well-differentiated papillary thyroid carcinoma (PTC), poorly differentiated thyroid carcinoma (PDTC), follicular thyroid carcinoma (FTC), anaplastic thyroid carcinoma (ATC), and medullary thyroid carcinoma (MTC). MTC is inherited as an autosomal dominant trait in 25% of cases. The genetic landscape of thyroid carcinoma has been largely deciphered. In PTC, genetic alterations have been found in about 95% of tumors: BRAF mutations and RET rearrangements are the main genetic alterations. BRAF and RAS mutations have been confirmed to play an important role also in PDTC and ATC, together with TP53 mutations that are fundamental in tumor progression. It has also been clearly demonstrated that telomerase reverse transcriptase (TERT) promoter mutations and TP53 mutations are present with a high-frequency in more advanced tumors, frequently associated with other mutations, and their presence, especially if simultaneous, is a signature of aggressiveness. In MTC, next-generation sequencing confirmed that mutations in the RET gene are the most common molecular events followed by H-RAS and K-RAS mutations. The comprehensive knowledge of the genetic events responsible for thyroid tumorigenesis is important to better predict the biological behavior and better plan the therapeutic strategy for specific treatment of the malignancy based on its molecular profile. [ABSTRACT FROM AUTHOR]

Simple Summary: The clinical behavior of medullary thyroid carcinoma is heterogeneous and can be influenced by several clinical, biochemical and molecular factors. The role of age as a prognostic factor remains controversial. In our cohort of 432 sporadic medullary thyroid carcinoma, no differences in histologic features at diagnosis and in number and type of therapies performed during the follow-up were detected when dividing the patients according to age (< and ≥ 65 years). Younger patients had a longer follow-up and survival time, compared to the older patients. However, in dead patients, no differences in the aggressiveness of the disease at presentation and treatments performed during the follow-up were found between the two age groups. Sporadic medullary thyroid carcinoma (MTC) is a rare malignancy with a heterogeneous clinical course. Several potential prognostic factors have been investigated, but the impact of some of these is controversial, such as age at diagnosis. We evaluated the data of 432 sporadic MTC patients followed-up for a median of 7.4 years. Patients were divided and compared according to their age at diagnosis in group A (<65 years—n = 338, 78.2%) and group B (≥65 years—n = 94, 21.8%). No differences were detected between the two groups. Median follow-up time was significantly longer in patients <65 than ≥65 years. We observed 41 (9.5%) cancer-related death events. The death rate was similar between the two age groups. However, the Kaplan Meier curve showed a longer survival time for younger patients compared to older patients [HR 2.5 (CI 95%: 1.27–4.94), p < 0.01]. Nevertheless, no differences in the aggressiveness of the disease at presentation and in the number and type of treatments performed were found in the two subgroups of dead patients. In patients with sporadic MTC, age at diagnosis did not correlate with any clinical and pathological features. Cancer-related death events are similar in older and younger patients, but survival time is longer in the younger. [ABSTRACT FROM AUTHOR]

Copy number variations (CNV) of the RET gene have been described in 30% of Medullary Thyroid Cancer (MTC), but no information is available about their role in this tumor. This study was designed to clarify RET gene CNV prevalence and their potential role in MTC development. RET gene CNV were analyzed in 158 sporadic MTC cases using the ION Reporter Software (i.e., in silico analysis) while the multiplex ligation-dependent probe amplification assay (i.e., in vitro analysis) technique was performed in 78 MTC cases. We identified three categories of RET ploidy: 137 in 158 (86.7%) cases were diploid and 21 in 158 (13.3%) were aneuploid. Among the aneuploid cases, five out of 21 (23.8%) showed an allelic deletion while 16 out of 21 (76.2%) had an allelic amplification. The prevalence of amplified or deleted RET gene cases (aneuploid) was higher in RET positive tumors. Aneuploid cases also showed a higher allelic frequency of the RET driver mutation. The prevalence of patients with metastatic disease was higher in the group of aneuploid cases while the higher prevalence of disease-free patients was observed in diploid tumors. A statistically significant difference was found when comparing the ploidy status and mortality. RET gene CNVs are rare events in sporadic MTC and are associated with RET somatic mutation, suggesting that they could not be a driver mechanism of tumoral transformation per se. Finally, we found a positive correlation between RET gene CNV and a worse clinical outcome. [ABSTRACT FROM AUTHOR]

Background: Pathogenic germline mutations affecting the RET proto-oncogene underlie the development of hereditary medullary thyroid carcinoma (MTC). The aims of this study were to evaluate the prevalence of germline RET mutations in a large series of MTC, collected over the last 25 years, and to reappraise their clinical significance. Methods: We performed RET genetic screening in 2031 Italian subjects: patients who presented with sporadic (n = 1264) or hereditary (n = 117) MTC, plus 650 relatives. Results: A RET germline mutation was found in 115/117 (98.3%) hereditary and in 78/1264 (6.2%) apparently sporadic cases: in total, 42 distinct germline variants were found. The V804M mutation was the most prevalent in our cohort, especially in cases that presented as sporadic, while mutations affecting cysteine residues were the most frequent in the group of clinically hereditary cases. All M918T mutations were "de novo" and exclusively associated with MEN2B. Several variants of unknown significance (VUS) were also found. Conclusions: a) RET genetic screening is informative in both hereditary and sporadic MTC; b) the prevalence of different mutations varies with V804M being the most frequent; c) the association genotype–phenotype is confirmed; d) by RET screening, some VUS can be found but their pathogenic role must be demonstrated before screening the family. [ABSTRACT FROM AUTHOR]

Medullary thyroid carcinoma (MTC) is a malignant tumor with challenging management. Multi-targeted kinase inhibitors (MKI) and tyrosine-kinase inhibitors (TKI) with high specificity for RET protein are approved for advanced MTC treatment. However, their efficacy is hindered by evasion mechanisms of tumor cells. Thus, the aim of this study was the identification of an escape mechanism in MTC cells exposed to a highly selective RET TKI. TT cells were treated with TKI, MKI, and/or the HH-Gli inhibitors, GANT61 and Arsenic Trioxide (ATO), in the presence or absence of hypoxia. RET modifications, oncogenic signaling activation, proliferation and apoptosis were assessed. Additionally, cell modifications and HH-Gli activation were also evaluated in pralsetinib-resistant TT cells. Pralsetinib inhibited RET autophosphorylation and RET downstream pathways activation in normoxic and hypoxic conditions. Additionally, pralsetinib impaired proliferation, induced the activation of apoptosis and, in hypoxic cells, downregulated HIF-1α. Focusing on escape molecular mechanisms associated with therapy, we observed increased Gli1 levels in a subset of cells. Indeed, pralsetinib stimulated the re-localization of Gli1 into the cell nuclei. Treatment of TT cells with both pralsetinib and ATO resulted in Gli1 down-regulation and impaired cell viability. Moreover, pralsetinib-resistant cells confirmed Gli1 activation and up-regulation of its transcriptionally regulated target genes. Altogether, we showed that pralsetinib impairs MTC cell growth and induces cell death, also in hypoxic conditions. The HH-Gli pathway is a new molecular mechanism of escape to pralsetinib therapy that can be overcome through combined therapy. [Display omitted] • Pralsetinib overcomes the limitations of cabozantinib in hypoxic MTC cells. • MTC triggers the RET-independent HH-Gli pathway as resistance mechanism to pralsetinib. • MTC models resistant to therapy were established after prolonged use of pralsetinib. • Pralsetinib and HH-Gli inhibition targets MTC subpopulations resistant to therapy. [ABSTRACT FROM AUTHOR]

Abstract: Medullary thyroid carcinoma (MTC) is an uncommon malignant tumor arising from the calcitonin-producing parafollicular cells (C cells) of thyroid. It accounts for 5–10% of all thyroid cancers, and it mostly occurs as a sporadic entity (sMTC), but a familial pattern (fMTC) is also possible. RET proto-oncogene germline mutations are crucial for the onset and the progression of fMTC, and the occurrence of single nucleotide polymorphisms could predispose to the sporadic form. In order to clarify the role of this gene in MTC, we carefully reviewed the PubMed database using appropriate terms. First, we summarized current knowledge of the germline RET mutations, mutation spectrum, and prevalence. We then performed a meta-analysis on the available case-control association studies for sMTC. Finally, we carried out in silico predictions of the best associated variants in the attempt to better define their role in the disease. To date, a total of 39 different RET germline mutations have been identified in fMTC families. The most affected codons are 609, 611, 618, 620 (exon 10) and 634 (exon 11), encoding for the extracellular cysteine-rich domain, and codons 768 (exon 13) and 804 (exon 14) of the intracellular tyrosine kinase domain. Six polymorphisms with at least three studies were included in the meta-analysis (A45A [rs1800858], G691S [rs1799939], L769L [rs1800861], S836S [rs1800862], S904S [rs1800863], and IVS1-126G>T [rs2565206]). The meta-analysis demonstrated a modest association of sMTC susceptibility with S836S and a strong association with the IVS1-126G>T polymorphism. Besides RET polymorphisms, we also investigated the role of a few other low-penetrance alleles of genes involved in the RET pathway or in xenobiotic metabolism, but none of these were confirmed. Thus, despite the well-known molecular basis of fMTC, the genetic variants of the sporadic form are still poorly understood, and functional analyses are needed to better understand the consequence of such RET variants and to improve our knowledge on the disease. [Copyright &y& Elsevier]

Abstract: About 30% of hereditary Medullary Thyroid Carcinoma (MTC) have been demonstrated to harbour imbalance between mutant and wild-type RET alleles. We studied the RET copy number alterations (RET CNA) in 65 MTC and their correlation with RET mutation and patients’ outcome. Fluorescence in situ Hybridization and Real-time PCR revealed RET CNA in 27.7% MTC but only in a variable percentage of cells. In sporadic MTC, RET CNA were represented by chromosome 10 aneuploidy while in hereditary MTC by RET amplification. A significant higher prevalence of RET CNA was observed in RET mutated MTC (P =0.003). RET CNA was also associated to a poorer outcome (P =0.005). However, the multivariate analysis revealed that only RET mutation and advanced clinical stage correlated with the worst outcome. In conclusion, 30% MTC harbour RET CNA in variable percentage of cells suggesting cell heterogeneity. RET CNA can be considered a poor prognostic factor potentiating the poor prognostic role of RET mutation. [Copyright &y& Elsevier]