Plasma levels of calcitonin in medullary thyroid carcinoma patients with and without the RET proto-oncogene mutations in exons 10 and 11

Thyroid carcinoma is the most common endocrine malignancy and approximately accounts 2% of all cancer cases. Medullary thyroid cancer (MTC) is an endocrine tumor with differentiation of Parafollicular or C-cells and is categorized into hereditary or sporadic types. Medullary thyroid carcinoma approximately accounts for 5-10% of all thyroid carcinoma. Germ-line and somatic mutations in exons 10 and 11 RET (Rearranged during Transfection) proto-oncogene are responsible for the occurrence of the familial and sporadic types, respectively. Calcitonin is a key marker in MTC diagnose and has been demonstrated to be highly sensitive for differential diagnosis prognostic assessment, follow-up and evaluation of MTC treatment. The aim of this study was to investigate the relationship between plasma levels of calcitonin in MTC patients with or without RET mutation.
In this cross-sectional study, the population consist of MTC patients who have referred to the endocrine and metabolism research center of Shahid Beheshti University of medical sciences since October 2013 till October 2016. Genomic DNA was extracted from peripheral blood leucocytes using the standard salting out/proteinase K method. Nucleotide change detection in exons 10 and 11 was performed using polymerase chain reaction (PCR) and direct DNA sequencing methods. Participants were then divided into two groups with or without mutation (43 individuals in each group). Plasma calcitonin levels were determined by enzyme-linked immunosorbent assay (ELISA) method in both groups.
Evaluation of the level of plasma calcitonin in 43 patients with a molecular mutation in RET proto-oncogene (mean age 31 years) and 43 patients without molecular mutations in RET proto-oncogene (mean age 43 years) were 7.6 pmol/mL and 3.07 pmol/mL respectively. This difference is statistically significant (P=0.0014).
Routine measurement of calcitonin has been investigated as a screening method for the diagnosis of medullary thyroid carcinoma patients. Nevertheless, additional data are required to definitely support routine measurement of calcitonin due to the role of RET proto-oncogene.