Endocrine Abstracts

Introduction: Cell-free DNA (cfDNA) integrity in plasma has been investigated as a non-invasive marker in cancer. Thyroid cancer the most common endocrine malignancy sometimes presents as indeterminate nodules and difficult to diagnose without histopathology.

Aim of the study: The present study aims to test the hypothesis that the presence of longer DNA strands circulating in plasma can be considered a marker for thyroid cancer.

Methods: Patients presenting with thyroid nodules underwent ultrasonography with Thyroid Image Reporting and Data Systems (TIRADS) scoring and FNAC (Bethesda classification). All patients in Bethesda 3,4,5,6 underwent surgery and histopathological confirmation. Patients in Bethesda 2 (cosmetic concerns, compressive symptoms) underwent surgery, rest were presumed benign on the basis of USG, FNAC features and clinical follow-up. Cell-free DNA was extracted from plasma and quantified. We adopted a quantitative real-time PCR (qPCR) approach based on the quantification of two amplicons of different length (67 and 180 bp respectively) to evaluate the integrity index 180/67 for APP gene. The genomic DNA isolated from the MDA-T32 papillary thyroid cancer cell line was used as reference to determine the relative DNA strand integrity because culture cells contained highly intact genomic DNA. The Ct value of the 180 bp for a sample was subtracted from that for the MDA-T32 control to obtain a (ΔCt) value for 180 bp. Likewise, the Ct value of a 67 bp for the sample was subtracted from that for the MDA-T32 control to obtain a (ΔCt) value for 67 bp. CfDNA Integrity index was calculated by ratio of ΔCt180/ΔCt 67 bp.

Results: A total of 131 subjects were recruited, of these 72 were benign and 59 had differentiated thyroid cancer proven by histopathology. CfDNA integrity index was higher in differentiated thyroid carcinoma patients (median 0.45, 95% CI: 0.36-0.52) than in subjects with benign nodules (median 0.32, 95% CI: 0.27-0.39). The cell free DNA integrity index 180/67 was significantly higher in malignant nodules compared and benign nodules (P=0.001).

Conclusions: CfDNA integrity index 180/67 could be a parameter for monitoring cfDNA fragmentation in thyroid cancer patients and a promising marker in the diagnosis of thyroid nodules that warrants further validation in future prospective trials.