Yield and costs of molecular diagnostics on thyroid cytology slides in the Netherlands, adapting the Bethesda classification

Detection of the BRAFV600E Mutation in Circulating Free Nucleic Acids as a Biomarker of Thyroid Cancer: A Review

Background: Liquid biopsy is a method that could potentially improve the management of thyroid cancer (TC) by enabling the detection of circulating tumor DNA and RNA (ctDNA, ctRNA). The BRAFV600E mutation appears to be the most representative example of a biomarker in liquid biopsy, as it is the most specific mutation for TC and a target for molecular therapeutics. The aim of this review is to summarize the available data on the detection of the BRAFV600E mutation in liquid biopsy in patients with TC. Methods: A comprehensive analysis of the available literature on the detection of the BRAFV600E mutation in liquid biopsy in TC was performed. Thirty-three papers meeting the inclusion criteria were selected after full-text evaluation. Results: Eleven papers discussed correlations between BRAF mutation and clinicopathological characteristics. Nine studies tested the utility of BRAFV600E detection in the assessment of residual or recurrent disease. Seven studies investigated BRAF-mutated circulating tumor nucleic acids (ctNA) as a marker of response to targeted therapy. In seven studies the method did not detect the BRAFV600E mutation. Conclusions: This review shows the potential of BRAFV600E-mutated ctNA detection in monitoring disease progression, particularly in advanced TC. The diagnostic value of BRAFV600E-mutated ctNA detection appears to be limited to advanced TC. The choice of the molecular method (quantitative PCR [qPCR], droplet digital polymerase chain reaction [ddPCR], and next-generation sequencing [NGS]) should be made based on the turnaround time, sensitivity of the test, and the clinical indications. Despite the promising outcomes of some studies, there is a need to verify these results on larger cohorts and to unify the molecular methods.

The evolving role of interventional cytopathology from thyroid FNA to NGS: Lessons learned at Federico II University of Naples

Fine-needle aspiration (FNA) guided by ultrasound (US) has emerged as a highly precise diagnostic method for managing thyroid nodules, significantly diminishing unnecessary surgeries. The effectiveness of US-guided FNA is high when a single specialist performs the FNA procedure and the microscopy. This paradigm has paved the way for the evolution of interventional cytopathology, a specialist with a pivotal role in the preoperative diagnostic process, encompassing patient history review, clinical examination, FNA execution under US guidance, preparation, and microscopic interpretation of cytological samples. As the landscape of precision medicine unfolds, molecular testing assumes greater importance in thyroid cytopathology, particularly in refining the risk of malignancy for indeterminate nodules. The updated Bethesda classification system underscores the clinical significance of molecular tests, emphasizing their role in refining diagnostic accuracy. With this evolving landscape, interventional cytopathologists must adapt by acquiring expertise in molecular technologies and addressing ongoing challenges in workflow harmonization and optimization. This paper delves into our decade-long experience as interventional cytopathologists, focusing on recent endeavours to ensure adequate samples not only for microscopic diagnosis but also for molecular testing. Additionally, here we review the challenges of integrating next-generation sequencing (NGS) technology into clinical practice, highlighting the importance of integrating clinically meaningful molecular data into comprehensive molecular cytology reports.

Molecular Diagnostics and [18F]FDG-PET/CT in Indeterminate Thyroid Nodules: Complementing Techniques or Waste of Valuable Resources?

Background: An accurate preoperative workup of cytologically indeterminate thyroid nodules (ITN) may rule out malignancy and avoid diagnostic surgery for benign nodules. This study assessed the performance of molecular diagnostics (MD) and 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG)-positron emission tomography/computed tomography (PET/CT) in ITN, including their combined use, and explored whether molecular alterations drive the differences in [18F]FDG uptake among benign nodules. Methods: Adult, euthyroid patients with a Bethesda III or IV thyroid nodule were prospectively included in this multicenter study. They all underwent MD and an [18F]FDG-PET/CT scan of the neck. MD was performed using custom next-generation sequencing panels for somatic mutations, gene fusions, and copy number alterations and loss of heterozygosity. Sensitivity, specificity, negative and positive predictive value (NPV, PPV), and benign call rate (BCR) were assessed for MD and [18F]FDG-PET/CT separately and for a combined approach using both techniques. Results: In 115 of the 132 (87%) included patients, MD yielded a diagnostic result on cytology. Sensitivity, specificity, NPV, PPV, and BCR were 80%, 69%, 91%, 48%, and 57% for MD, and 93%, 41%, 95%, 36%, and 32% for [18F]FDG-PET/CT, respectively. When combined, sensitivity and specificity were 95% and 44% for a double-negative test (i.e., negative MD plus negative [18F]FDG-PET/CT) and 68% and 86% for a double-positive test, respectively. Concordance was 63% (82/130) between MD and [18F]FDG-PET/CT. There were more MD-positive nodules among the [18F]FDG-positive benign nodules (25/59, 42%, including 11 (44%) isolated RAS mutations) than among the [18F]FDG-negative benign nodules (7/30, 19%, p = 0.02). In oncocytic ITN, the BCR of [18F]FDG-PET/CT was mere 3% and MD was the superior technique. Conclusions: MD and [18F]FDG-PET/CT are both accurate rule-out tests when unresected nodules that remain unchanged on ultrasound follow-up are considered benign. It may vary worldwide which test is considered most suitable, depending on local availability of diagnostics, expertise, and cost-effectiveness considerations. Although complementary, the benefits of their combined use may be confined when therapeutic consequences are considered, and should therefore not routinely be recommended. In nononcocytic ITN, sequential testing may be considered in case of a first-step MD negative test to confirm that withholding diagnostic surgery is oncologically safe. In oncocytic ITN, after further validation studies, MD might be considered. Clinical Trial Registration: This trial is registered with ClinicalTrials.gov: NCT02208544 (August 5, 2014), https://clinicaltrials.gov/ct2/show/NCT02208544.

Is There a Role for Molecular Testing for Low-Risk Differentiated Thyroid Cancer? A Cost-Effectiveness Analysis

Molecular testing for thyroid nodules has been rapidly developed in recent years, aiming to predict the presence of malignancy and aggressive features. While commonly utilized to predict malignancy, its role in guiding the management approach is still developing. The high cost of genetic tests and long-term sequences of thyroid cancer is limiting to real-life studies. Objective: To evaluate the cost effectiveness of molecular testing for low-risk differentiated thyroid cancer (lrDTC). Methods: We developed a Markovian decision tree model of a simulated lrDTC cohort, comparing two management strategies: (I) Conducting genetic tests (GT)-patients are stratified into three risk groups for distant metastasis by the identified molecular markers: low-, intermediate- and high-risk molecular profile; followed by management accordingly: patients with low-risk will undergo hemithyroidectomy (HT), patients with intermediate-risk will undergo total thyroidectomy (TT), and high-risk patients will undergo TT with central neck dissection; (II) Without genetic tests (wGT)-all patients will undergo HT according to the ATA recommendations for lrDTC. Outcomes were measured as quality-adjusted life years (QALYs) and costs of each strategy. Results: GT was found as cost effective, leading to a gain of 1.7 QALYs with an additional cost of $327 per patient compared to wGT strategy. This yielded an incremental cost-effectiveness ratio of $190 per QALY. Sensitivity analysis demonstrated robust results across the variables' ranges. The most impactful variable was the benefit from performing TT rather than HT for intermediate to high-risk patients. Conclusions: Our model found that molecular testing for lrDTC is cost-effective, allowing tailored management according to the patient's personal risk level reflected in the genetic profile, hence improving outcomes.

FDG-PET/CT in indeterminate thyroid nodules: cost-utility analysis alongside a randomised controlled trial

PURPOSE

To evaluate cost-effectiveness of an [¹⁸F]FDG-PET/CT-driven diagnostic workup as compared to diagnostic surgery, for thyroid nodules with Bethesda III/IV cytology. [¹⁸F]FDG-PET/CT avoids 40% of futile diagnostic surgeries for benign Bethesda III/IV nodules.

METHODS

Lifelong societal costs and quality-adjusted life years (QALYs) were assessed for 132 patients participating in a randomised controlled multicentre trial comparing [¹⁸F]FDG-PET/CT to diagnostic surgery. The observed 1-year trial results were extrapolated using a Markov model. The probability of cost-effectiveness was estimated using cost-effectiveness acceptability curves, taking uncertainty about sampling, imputation, and parameters into account.

RESULTS

The observed 1-year cost difference of [¹⁸F]FDG-PET/CT as compared to diagnostic surgery was - €1000 (95% CI: - €2100 to €0) for thyroid nodule-related care (p = 0.06). From the broader societal perspective, the 1-year difference in total societal costs was - €4500 (- €9200 to €150) (p = 0.06). Over the modelled lifelong period, the cost difference was - €9900 (- €23,100 to €3200) (p = 0.14). The difference in QALYs was 0.019 (- 0.045 to 0.083) at 1 year (p = 0.57) and 0.402 (- 0.581 to 1.385) over the lifelong period (p = 0.42). For a willingness to pay of €50,000 per QALY, an [¹⁸F]FDG-PET/CT-driven work-up was the cost-effective strategy with 84% certainty.

CONCLUSION

Following the observed reduction in diagnostic surgery, an [¹⁸F]FDG-PET/CT-driven diagnostic workup reduced the 1-year thyroid nodule-related and societal costs while sustaining quality of life. It is very likely cost-effective as compared to diagnostic surgery for Bethesda III/IV nodules.

TRIAL REGISTRATION NUMBER

This trial is registered with ClinicalTrials.gov: NCT02208544 (5 August 2014), https://clinicaltrials.gov/ct2/show/NCT02208544 .

Yield and costs of molecular diagnostics on thyroid cytology slides in the Netherlands, adapting the Bethesda classification

Objective

To evaluate our institutional experience with molecular diagnostics (MD) on thyroid cytology smears, evaluate the costs and describe MD guided clinical management of indeterminate Bethesda III/V thyroid nodules.

Methods

We performed a retrospective review of 164 Bethesda III or V thyroid cytopathology reports subjected to MD from 2013 to 2020, that altered Bethesda classification or management. MD consisted of mutation and gene fusion analysis by next‐generation sequencing (NGS) of morphologically analysed and selected cytological slides. Findings were modelled to nationwide data on Bethesda incidences from ‘the Dutch Pathology Registry’ PALGA, and costs were estimated.

Results

82 of 164 cases received an upgrade in Bethesda class. Twenty cases changed from Bethesda III to IV/V, 62 from Bethesda III or V to VI, and 72 remained unaltered. We estimate net savings with implementing MD, by preventing 454 repeat cytology and 326 (diagnostic) hemithyroidectomies, to be at least 2 million Euro annually in the Netherlands. Per Bethesda III and V patient, net savings would be about 100 Euro and 4100 Euro, respectively.

Conclusion

NGS‐based MD on nucleic acids extracted directly from cytology slides is a feasible and cost saving tool for personalized management in indeterminate Bethesda III/V thyroid cytology. Based on the interpretation of our retrospective data, we assume that this approach results in less disease burden for the patient, reduced surgical interventions and complication risks, reduced sick leave, among others. Further evaluation of structural implementation of the presented approach in routine thyroid Bethesda III/V cytology in a prospective setting is warranted.