CALCITONIN REVISITED IN 2020

Approach to the Patient: Hereditary Medullary Thyroid Carcinoma

Medullary thyroid carcinoma is a rare neuroendocrine tumor originating from calcitonin-secreting parafollicular C cells of the thyroid gland. Approximately 25% of cases in adults are hereditary medullary thyroid carcinoma (hMTC), arising from activating, germline pathogenic variants in the REarranged during Transfection (RET) proto-oncogene and causing the syndromes multiple endocrine neoplasia (MEN) types 2A and 2B. A paradigmatic feature of MEN2 is its robust genotype-phenotype correlations, which predict the disease spectrum and age of onset of hMTC and other clinical manifestations. Advances in genetic testing and systemic therapies and an improved understanding of the natural course of MEN2 have transformed the clinical presentation of hMTC from advanced-stage disease to early detection in asymptomatic RET pathogenic variant carriers. The management of hMTC has similarly evolved from aggressive, one-size-fits-all surgical approaches to personalized strategies informed by genotype, biochemical markers, and imaging findings. Risk-reducing early thyroidectomy remains the cornerstone of metastatic hMTC prevention, with the timing of surgery tailored to the specific pathogenic variant and clinical context. Additionally, recent advances in targeted systemic therapies offer promising options for patients with recurrent and/or metastatic disease. This "Approach to the Patient" article explores the diagnostic evaluation, surgical decision-making, systemic treatment options, and follow-up of patients with hMTC, emphasizing the critical role of multidisciplinary care in optimizing outcomes for patients and their families.

Medullary Thyroid Cancer: Updates and Challenges

A personalized approach to the management of medullary thyroid cancer (MTC) presents several challenges; however, in the past decade significant progress has been made in both diagnostic and treatment modalities. Germline rearranged in transfection (RET) testing in multiple endocrine neoplasia 2 and 3, and somatic RET testing in sporadic MTC have revolutionized the treatment options available to patients. Positron emission tomography imaging with novel radioligands has improved characterization of disease and a new international grading system can predict prognosis. Systemic therapy for persistent and metastatic disease has evolved significantly with targeted kinase therapy especially for those harboring germline or somatic RET variants. Selpercatinib and pralsetinib are highly selective RET kinase inhibitors that have shown improved progression-free survival with better tolerability than outcomes seen in earlier multikinase inhibitor studies. Here we discuss changes in paradigms for MTC patients: from determining RET alteration status upfront to novel techniques for the evaluation of this heterogenous disease. Successes and challenges with kinase inhibitor use will illustrate how managing this rare malignancy continues to evolve.

Correction factor between two calcitonin assays: DiaSorin LiaisonXL and Cobas E601

Introduction: Calcitonin measurement is important for the diagnosis and monitoring of medullary thyroid carcinoma. Unfortunately, in clinical practice, different detection systems assays are used in the follow-up of the patients, which can be misleading.

Objective: To identify the correction factor for calcitonin measurement on two different immunoanalysers: DiaSorin-LiaisonXL (immunochemiluminescence) and CobasE601 (electro-immunochemiluminescence).

Methods: We selected 89 registered CT samples (28-from men; 61-from women), that were analysed on CobasE601 with reported values between 0.5 pg/ml and 2812 pg/ml (128.5±513.98). These CT samples were selected randomly to cover as wide a range of values as possible, and represented either basal CT (n=38) or selected from CT stimulation tests (n=51). Samples were evaluated subsequently on DiaSorin-LiaisonXL. All patients gave their informed consent.

Results: Between the two assays a segmented linear correlation was noted. We identified the following general linear regression equation: 1.108x+19.337 (p<0.05). The bias increased at high calcitonin values. Therefore, for a better accuracy we analysed the regression equation segmentally. A statistic difference (p<0.05) was noted for CT values ranged between 350-2600 pg/ml (n=31) on DiaSorin-LiaisonXL, for which the linear regression equation for CobasE601 becomes 1.009x+169.796.

Conclusions: Calcitonin correction factors are highly important in the dynamic follow up of a patient suffering from medullary thyroid carcinoma when different detection systems assays are used to determine calcitonin. We identified the correction factors for calcitonin determination between two different frequently used chemiluminescence immunoanalysers: DiaSorin-LiaisonXL and CobasE601. However, it is strongly advisable to use the same analyser in order to establish biochemical evolution of calcitonin.

Diagnostic Challenges of Medullary Thyroid Carcinoma

BACKGROUND

Medullary thyroid carcinoma (MTC) comprises 1-2% of all thyroid cancers, yet 15% of all thyroid cancer-related deaths. While up to 20% of cases may be predicted due to autosomal dominant germline mutations, 80% of cases are sporadic. However, due to non-specific presenting symptoms and diagnostic imaging, prompt diagnosis and treatment has remained elusive. This article will further investigate the limitations of MTC diagnosis and look into future areas for diagnostic improvement.

METHODS

Relevant articles were identified using a systematic PubMed and Google Scholar search.

RESULTS

Prophylactic total thyroidectomy for the 20% of MTC cases that are present in autosomal dominant disorder provides definitive treatment. Serum calcitonin (Ctn) screening has several technical limitations due to population variability and laboratory assay interference, but advances in laboratory technology and combined use with fine needle aspiration increase its sensitivity. Other serum assays such as carcinoembryonic antigen and procalcitonin have limited applicability. Thyroid ultrasound remains the gold standard for the initial diagnostic planning, with limited application for CT, MRI, and PET imaging.

CONCLUSION

With complete surgical resection the only definitive treatment, early MTC diagnosis has presented an elusive challenge, mainly due to its relative rarity and difficulty in finding an economic screening strategy. Careful family history combined with fine needle aspiration with serum Ctn analysis can improve diagnostic sensitivity and specificity to greater than 95%.

ACTUALITIES IN ENDOCRINE PHARMACOLOGY: ADVANCES IN THE DEVELOPMENT OF ORAL FORMULATIONS FOR CALCITONIN AND SEMAGLUTIDE

As the medical utility of injectable therapeutic peptides is expanding, so is the challenge of developing technologies that allow the administration of such molecules via alternative routes, considering that chronic patients requiring treatment with parenteral formulations are less adherent and compliant to the therapeutic regimens. Hence, substantial efforts have been made to develop technologies that allow the oral formulation of peptides. Due to their importance in the field of pharmaceutical technology, we describe the latest advancements made in the development of oral salmon calcitonin and oral semaglutide, in co-formulation with absorption enhancers such as 8-[(5-chloro-2-hydroxybenzoyl) amino] octanoic acid (or 5-CNAC) and N-[8-(2-hydroxybenzoyl) amino] caprylate (or SNAC). Oral semaglutide is considered to be a landmark for oral peptide delivery technology, as it is one of the very few successful examples of peptides that can be administered orally. Unlike semaglutide, oral calcitonin is still not approved by the regulatory authorities because it failed to demonstrate the anticipated effects in phase III clinical trials conducted so far. However, the efforts for obtaining an oral form of calcitonin have significantly contributed to the development of technologies that facilitate the absorption of peptide-structure macromolecules.

Updates in the advances of sporadic medullary thyroid carcinoma: from the molecules to the clinic

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine malignancy that originates in parafollicular cells. It is well-known that a quarter of MTC are involved in hereditary multiple endocrine neoplasia type 2 syndromes, whereas most MTC are sporadic. Unlike the commonly encountered gastrointestinal or pulmonary neuroendocrine tumors, most sporadic MTCs have distinct genetic alterations featured by somatic changes of either Rearranged during Transfection (RET) or RAS point mutation. The increasing application of next-generation sequencing, whole-exome sequencing, and other molecular detection techniques enables us to understand MTC comprehensively concerning its detailed molecular changes and their clinical correlations. This article reviews the advances in genetic alterations and their prognostic impact in sporadic MTC among different populations and discusses the associated tumor immune microenvironments and the potential role of immunotherapy targeting PD-L1/PD-1 in treating MTC. Furthermore, the current multikinase inhibitor targeting therapy for sporadic MTC has been summarized here and its efficacy and drug toxicity are discussed. Updates in advance of the role of calcitonin/procalcitonin/calcitonin-related polypeptide alpha (CALCA) gene transcripts in diagnosing and handling MTC are also mentioned. The treatment of advanced MTC is still challenging and might require a combination of several modalities.