Written by Laurie Tarkan With commentary by Robert Ferris, MD, PhD, professor and chief of the Division of Head and Neck Surgery in University of Pittsburgh School of Medicine
The number of thyroid surgeries for suspected cancer has dramatically risen in recent years, and several new molecular thyroid cancer tests may be able to slow the trend. The total number of thyroid surgeries performed in the United States due to suspicious thyroid nodules increased from 99,613 to 130,216 between 2006 and 2011, according to a 2013 study. But experts believe many thyroid surgeries are performed unnecessarily.
Thyroid cancers are often slow growing and many don’t grow much at all and never become harmful. In addition, ambiguous results from fine needle biopsies, the first line of testing, contribute to the overuse of surgical biopsies.
Cancer in the thyroid, which is located in the lower area of the neck, is the fifth most common cancer diagnosed in women. But many of these cancers may never be problematic if left alone.
The American Thyroid Association is updating their 2009 guidelines for the management of thyroid cancer in an effort to rein in the surgeries and provide more appropriate care. The guidelines, which will be published this fall, will reference a statement on the use of molecular tests for thyroid nodules that are considered ambiguous.
Thyroid nodules are extremely common, but patients with thyroid nodules that grow to 1 to 2 cm., depending on other characteristics and risk factors, often have a needle biopsy to test for cancer, explains Robert Ferris, MD, PhD, professor and chief of the Division of Head and Neck Surgery in University of Pittsburgh School of Medicine.
The biopsied tissue is then classified as benign or cancerous, but about 20 to 30 percent are classified as “indeterminate.” Those patients with uncertain results are often told to surgically remove the thyroid or have a partial surgery, or lobectomy, to be on the safe side. But the new molecular tests can determine if a nodule is low risk and unlikely to grow to the size to cause problems.
Looking to Molecular Testing“Minimally invasive molecular testing for thyroid cancer has improved by leaps and bounds in the last several years,” said Dr. Ferris, who is co-author of the new statement regarding molecular testing.
One of the commercially available tests, called the Afirma test, can rule out cancer with a high rate of accuracy on indeterminate tests. It looks at the levels of expression of 142 genes and can predict low risk nodules. “If the test result is ‘likely benign,’ a patient can avoid getting surgery,” says Dr. Ferris.
Another test developed by the University of Pittsburgh, called ThyroSeq v2.0, allows pathologists to simultaneously test for multiple genetic markers of thyroid cancer. It looks at mutations of up to 60 single base oncogenes, which are thought to turn on the growth of the nodule and cause malignant behavior, explains Dr. Ferris. This test can not only rule out non-cancerous nodules, but it can also accurately identify cancers with 80 to 100% accuracy. In the future, the test will likely help differentiate between very high risk malignancies that would require surgery and low-risk malignancies which could take more of a wait and see approach.
A common approach today for someone with a suspicious nodule or a small thyroid cancer that shows no signs of spread beyond the thyroid gland is to have a lobectomy, the removal of the right or left lobe where the nodule is located, sparing the rest of the thyroid. If the biopsy is then graded as high risk, the patient would go back in for a second surgery to remove the rest of the thyroid. The ThyroSeq v2.0 can help people avoid that two step process by assessing the risk of the tumor from the needle biopsy sample. “The Pittsburgh test can determine if you have an 80 to 100% risk of cancer and can offer the patient a total thyroidectomy up front, to avoid two surgeries,” Dr. Ferris says.
“Thousands of thyroidectomies could be avoided and thousands of two-step procedures could be avoided every year if we adapted these tests,” he says. “We need to educate the doctors out there that these molecular tests are valuable.”
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