Benign thyroid nodules can be identified with genetic test
A Gene Expression Classifier (GEC) test can drastically reduce unnecessary surgeries in thyroid nodule assessment, according to a new study. These indeterminate nodules are being evaluated with a new molecular diagnostic test that measures the expression levels of 142 genes. This test is able to identify which initially indeterminate nodules are highly likely to be benign, and thus allows patients to avoid unnecessary diagnostic surgery.
This multisite study was co-led by Bryan R. Haugen, MD, of the University of Colorado School of Medicine in Aurora. It provides the first long-term look at how these patients fared, and its findings reaffirm the performance of the Afirma GEC.
The study findings suggest the accuracy of a benign diagnosis via GEC is comparable to a benign diagnosis via cytopathology. “This fact and the degree to which physicians and patients in the study opted against surgery when the molecular test result was benign underscore the test's potential to drastically reduce the problem of unnecessary surgeries in thyroid nodule assessment," said Haugen.
Researchers analyzed all patients who had received Afirma GEC testing following indeterminate fine needle aspiration (FNA) biopsy results at five academic medical centers between 2010 and 2013. The GEC identified 174 of 339 (51%) indeterminate nodules as benign and, among these, 71 had documented clinical follow-up for an average of 9 months. Of these, only one nodule proved cancerous, demonstrating a very high negative predictive value (NPV) for the GEC. This finding is consistent with results from an earlier prospective, multicenter clinical study.
Additionally, in the new study only 6% of patients with nodules identified as benign by the GEC test underwent surgery. This is a substantial reduction compared to traditional surgical rates for patients with cytologically indeterminate thyroid nodules.
Thyroid nodules are common, but only approximately 5% to 15% prove malignant. Most nodules are evaluated using FNA, with approximately 525,000 thyroid nodule FNAs performed in the United States in 2011 to rule out cancer. In most cases, the results are benign, yet in approximately 15% to 30% of cases the results are indeterminate (ie, not clearly benign or malignant). Because of the risk of thyroid cancer, most of these patients have historically been recommended for surgery to remove all or part of the thyroid to obtain a final diagnosis. However, such indeterminate nodules ultimately prove benign in 70% to 80% of cases. For these patients, the surgery was not needed and they were unnecessarily exposed to the cost, risk, and morbidity of this intervention. Additionally, most patients subsequently require lifelong thyroid hormone therapy.
The study was published online in the Journal of Clinical Endocrinology & Metabolism (2013; doi:10.1210/jc.2013-2482).