Plasma Cell-Free DNA to Differentiate Malignant from Benign Thyroid Nodules

Role of Genetic Testing in the Management of Indeterminate Thyroid Nodules in the Indian Setting

The increased detection of thyroid nodules in the human population has led to an increase in the number of thyroid surgeries without an improvement in survival outcomes. Though the choice for surgery is straightforward in malignant thyroid nodules, the decision is far more complex in those nodules that get categorized into indeterminate thyroid nodules (ITN) by fine needle aspiration. Therefore, there is a pressing need to develop a tool that will aid in decision-making among the ITN. In this context, the development of various molecular testing (MT) panels has helped to confirm or rule out malignancy, reducing unnecessary surgeries and potentially guiding the extent of surgery as well. Currently, such tests are widely used among the Western population but these MT panels are not used by the South Asian population because of non-availability of validated panels and the high cost involved. There is a need to develop a suitable panel which is population-specific and validate the same. In this review, we would focus on current trends in the management of ITN among the South Asian population and how to develop a novel MT panel which is cost-effective, with high diagnostic accuracy obviating the need for expensive panels that already exist.

Molecular testing in indeterminate thyroid nodules: an additional tool for clinical decision-making

Thyroid nodules are commonly encountered in clinical practice, affecting up to 50% of the population. The large majority of thyroid lumps are benign incidental findings detected by imaging, while approximately 5-15% harbor malignancy. For a target patient's care, it is of paramount importance to identify and treat thyroid malignancy, while preventing unnecessary invasive surgery in patients with benign lesions. Although fine needle aspiration (FNA) associated with cytological examination provides malignant risk information, 20-30% of diagnoses fall into the "indeterminate thyroid nodule" (ITN) category. ITN clinical management remains a challenging issue for physicians since the ITN risk of malignancy varies from 5% to 40% and most thyroid nodules undergo overtreatment with surgery procedures. ITN molecular testing may better define malignant risk in the single nodule and is able to discriminate with accuracy benign from malignant nodules. Nowadays there are different technologies and different molecular panels, each with its own specificity, sensitivity and predictive values. In view of widespread introduction of molecular testing , some outstanding questions remain and are addressed in the present review such as the presence of molecular panels acting as "rule in" or "rule out" tools, the effective impact of testing results in the clinical decision-making process, and the prohibitive cost of commercial assays associated with the lack of test reimbursement in national health systems.

Diagnostic value of cell-free DNA in thyroid cancer: A systematic review and meta-analysis

OBJECTIVE

An increasing number of studies have shown the potential diagnostic value of cell-free DNA (cfDNA) as a new biomarker in the management of thyroid cancer (TC); however, the accuracy of research results is inconsistent. This meta-analysis is the first to synthesize published results and evaluate the application value of circulating cfDNA in the diagnosis of TC.

METHODS

A search strategy was developed according to PICO (P: Patient; I: Intervention; C: Comparison; O: Outcome) principles. We searched 5 databases until October 2022. Original studies that examined cfDNA for the diagnosis of TC and used pathology as the gold standard were included in this meta-analysis. A random-effects model was used to pool the data extracted from individual studies, including the number of patients and the numbers of true positives, false positives, true negatives, and false negatives.

RESULTS

A total of 622 patients with TC, 547 patients with benign thyroid nodules, and 98 healthy individuals were included in 20 studies reported in 14 articles. The types of cfDNA included in the research include specific mutations of cfDNA, methylation of cfDNA, the content of cfDNA, and cfDNA index. After rigorous statistical analysis, the pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the summary receiver operating characteristic curve were 0.76 (95% confidence interval [CI] 0.62-0.85), 0.87 (95% CI 0.78-0.93), 5.08 (95% CI 3.3-10.3), 0.28 (95% CI 0.17-0.46), 21 (95% CI 9-49), and 0.89 (95% CI 0.86-0.91), respectively. The meta-regression results showed that the number of cfDNAs, cfDNA methylation status, and sample size were the sources of heterogeneity in the specificity of the study. A subgroup analysis showed that the quantitative analysis group (cfDNA level) had a higher diagnostic accuracy than that of the qualitative analysis group (cfDNA methylation, mutation, or integrity index), with a sensitivity of 0.84, specificity of 0.89, and area under the curve of 0.91.

CONCLUSIONS

The results of this meta-analysis suggest that cfDNA has value as an adjunct for the diagnosis of TC. Quantitative detection of cfDNA can achieve relatively high diagnostic accuracy. However, due to heterogeneity, the test results based on cfDNA for TC should be interpreted with caution.

Detection of driver mutations in plasma cell-free nucleic acids in differentiated thyroid neoplasm

IMPORTANCE

This proof-of-concept paper demonstrates that driver mutations can be detected in plasma in differentiated thyroid tumors, and we were able to detect mutations in upto 80% malignant thyroid nodules. Additionally, cancer subtypes could also be predicted using a 8-gene panel. In almost 90% follicular adenoma, rat sarcoma virus (RAS) mutations were detectable. There was a strong agreement between driver mutations found in plasma samples, FNAC materials, and histopathology samples. This has potential as a noninvasive, preoperative diagnostic tool (particularly of clinical importance in indeterminate nodules) and may help in detection of residual tumor after surgery. Future research is warranted to test the role of this tool to detect tumor recurrence.

OBJECTIVE

Ultrasonographic (USG) evaluation and fine-needle aspiration (FNA) are cornerstone for evaluation of thyroid neoplasm. Molecular technique including detection of driver mutation from FNA cytology (FNAC) material is an established modality. In this study, we explored the feasibility of using plasma cell-free nucleic acids to identify known driver mutations in differentiated thyroid neoplasm.

DESIGN

Patients presenting with thyroid nodules underwent USG with Thyroid Image Reporting and Data Systems 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, and rest were presumed benign on the basis of USG, FNAC features, and clinical followup.).

SETTING

Endocrinology clinic.

PARTICIPANTS

Subjects with thyroid nodule.

INTERVENTION(S) OR EXPOSURE(S)

None.

MAIN OUTCOME(S) AND MEASURE(S)

Plasma sample, FNA, and histopathology material were evaluated for driver mutations (8-gene panel comprising BRAF-V600E, RET/PTC3, RET/PTC1, TERT promoter, HRAS, NRAS, KRAS, and PAX8-PPARG).

RESULTS

A total of 223 subjects were recruited; of these 154 were benign and 69 had differentiated thyroid cancer. We were able to detect driver mutation from plasma in 55 subjects (79.71%) of all malignant patients, and 11 patients in benign category had RAS mutation (follicular adenoma). Rest of the benign nodules did not have any detectable driver mutations.

CONCLUSIONS AND RELEVANCE

Plasma might be a viable noninvasive alternative source for detection of driver mutations (8-gene panel) in subjects with differentiated thyroid tumors and may have significant clinical utility.

Cell-Free DNA Analysis within the Challenges of Thyroid Cancer Management

Simple Summary

Liquid biopsy is a minimally invasive method that emerged as a new promising tool for improving diagnosis, risk stratification, follow-up, and treatment of cancer patients. To date, the majority of the research in the area of liquid biopsy has focused on plasma-based cell-free DNA as a potential surrogate for tumor DNA obtained from a tissue biopsy. In the last decades, breakthrough advancements have been performed in the knowledge of thyroid cancer genetics, and the role of molecular characterization in clinical decision-making is continuously rising, from diagnosis completion to the personalization of treatment approach. Hence, it is expectable for cell-free DNA to be applicable in thyroid cancer management. This review aims to investigate the cell-free DNA utility for thyroid cancer patients’ care.

Abstract

Thyroid cancer is the most frequent endocrine malignancy with an increasing incidence trend during the past forty years and a concomitant rise in cancer-related mortality. The circulating cell-free DNA (cfDNA) analysis is a patient’s friendly and repeatable procedure allowing to obtain surrogate information about the genetics and epigenetics of the tumor. The aim of the present review was to address the suitability of cfDNA testing in different forms of thyroid cancer, and the potential clinical applications, as referred to the clinical weaknesses. Despite being limited by the absence of standardization and by reproducibility and validity issues, cfDNA assessment has great potential for the improvement of thyroid cancer management. cfDNA may support the pre-surgical definition of thyroid nodules by complementing invasive thyroid fine needle aspiration cytology. In addition, it may empower risk stratification and could be used as a biomarker for monitoring the post-surgical disease status, both during active surveillance and in the case of anti-tumor treatment.