After a nodule is discovered, a tiny tissue biopsy is taken with a needle, then evaluated under a microscope. If it's malignant, the thyroid is surgically removed.
But while the chance of cancer is about 1 in 10, the chance of an inconclusive biopsy result is about 1 in 3. As a result, about 75,000 people a year have their thyroids partly or completely removed, only to learn from more detailed testing that there was no cancer.
Afirma, made by San Francisco-based Veracyte, could prevent an estimated 25,000 of these unneeded surgeries. It analyzes the activity pattern of 142 genes in the biopsy sample, then classifies the tissue as benign or "suspicious."
In the validation study at Penn and 49 other sites, Afirma correctly classified 78 out of 85 malignant nodules as suspicious, and the misses were because of insufficient tissue samples.
Afirma also classified as suspicious 87 out of 180 samples that were actually benign, so it will not eliminate the overtreatment problem. But because Afirma reliably identifies cancer, a patient whose sample is classified "benign" can feel confident that surgery isn't necessary.
"It's not perfect, but it's the best thing we've have to date," said Susan J. Mandel, a Penn thyroid specialist who was part of the validation study. "This is a win-win."
On the market for 18 months, Afirma costs $4,000. That's not cheap, but it's about a third the cost of thyroid surgery — which may leave the patient needing lifelong hormone supplements. That's why Medicare and some other insurers are covering the test, said Veracyte co-founder Bonnie Anderson.
— Marie McCullough