307P - Development of circulating free DNA methylation markers for thyroid nodule diagnostics

Background

The incident rate of thyroid nodules has risen globally, thus it is critical to identify malignancy among benign lesions. Currently available molecular diagnostics for malignant nodules have not achieved the desired degree of accuracy. We aimed to identify DNA methylation markers to accurately classify benign and malignant nodules, and to develop tools for non-invasive screening of thyroid cancer.

Methods

Marker screening was performed on papillary thyroid cancer (PTC, 37 tissues, 55 plasmas), benign nodules (BTN, 37 tissues, 55 plasmas) and normal samples (20 buffy coats; 123 plasmas) by MONOD+ assay. We identified differential markers by Wilcox rank sum test using Benjamini-Hochberg procedure to control false discovery rate. Predication models were built using machine-learning algorithms including random forest and support vector machine. They were validated using public DNA methylation data of thyroid tissues. Candidate markers were developed into a targeted sequencing panel and were validated on plasma DNA samples (115 PTC, 102 BTN). Best-performing markers were developed into an improved panel to classify additional plasma DNA samples of malignant or benign thyroid nodules.

Results

From the MONOD+ data we identified over 1000 DNA methylation markers significantly differential between malignant and benign nodules. We built a classification model by random forest method, which classified DNA methylation profiles of thyroid nodules at a sensitivity of 90.5% and a specificity of 91.9% (95% CI, 0.91-1.0). We produced a targeted sequencing panel using those markers and sequenced plasma DNA of PTC and benign nodules. Two thirds of them were used as a training cohort to build a prediction model, which classified the remaining samples at an accuracy of 72%. We selected the best-performing markers to build an advanced version of panel, which classified additional over 500 plasma DNA samples of thyroid nodules with increased sequencing depth to improve the accuracy and consistency in classification.

Conclusions

Our study demonstrates that DNA methylation markers can robustly differentiate thyroid nodules based on their malignancy. They are thus promising candidates to develop non-invasive diagnostics for thyroid cancer screening.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The First Affiliated Hospital, Sun Yat-sen University.

Funding

The First Affiliated Hospital, Sun Yat-sen University.

Disclosure

Z. Su, Q. He: Shareholder/Stockholder/Stock options, Full/Part-time employment: Singlera Genomics. L. Cheng: Full/Part-time employment: Singlera Genomics. R. Liu: Leadership role, Shareholder/Stockholder/Stock options, Full/Part-time employment: Singlera Genomics. All other authors have declared no conflicts of interest.