Up to half of all adults have nodules (lumps) in their thyroid, a gland at the base of the neck, and for some people, this can be a sign of thyroid cancer, which if it is caught early is relatively easily treated. Diagnosis is invasive and ambiguous results can lead to unnecessary surgery, but Veracyte's Afirma Gene Expression Classifier test using genetic biomarkers could cut the number of operations by up to half, and reduce the associated stress, pain and costs, according to a study published in The New England Journal of Medicine and presented at ENDO 2012.
Thyroid nodules are checked for cancer using fine-needle aspiration (a sample taken using a thin hollow needle) from the thyroid nodule, but when the samples are looked at under the microscope, in up to a third of these it's not clear whether the cells are cancerous. The patients with indeterminate results are often sent for surgery to remove part or all of the thyroid just in case (around 75,000 operations in the U.S. a year), but most of the nodules turn out to be benign, leaving patients with avoidable pain and scarring, as well as needing thyroid replacement for the rest of their lives.
To compare the results from standard care and the genetic test, the researchers collected samples from 3,789 patients with thyroid nodules and any that were classified as "indeterminate" were assessed using Veracyte's gene expression test. The patients were treated as normal, with some undergoing surgery based on the physician's assessment, and any surgically removed tissue was screened by pathologists to confirm the presence or absence of cancer.
"Our results showed that the gene expression test can substantially reclassify otherwise inconclusive thyroid nodule cytology results," said co-principal study investigator Bryan Haugen of the University of Colorado. "When the gene expression test is benign, this conveys the same level of predictive accuracy comparable to patients who had a benign cytopathology result."
While the test isn't specific enough to be able to replace tissue sampling completely, the researchers believe that it is sufficiently able to predict the risk of cancer in the samples that are not clear cut. The researchers suggest that "a more conservative clinical approach" could be used for these patients whose results are not clear under the microscope and whose genetic results are negative.
However, while describing it as "a welcome addition to the tools available for informed decision making about the management of thyroid nodules," the editorial published alongside the study results does point out that there is a risk of false negatives (and therefore missed cancers) with the test, and that in the future adding in further molecular tests could improve the accuracy.