Little Difference Between Molecular Tests for Refining Thyroid Nodule Diagnosis

By David Douglas

December 21, 2020

NEW YORK (Reuters Health) - In patients in whom thyroid fine-needle aspiration (FNA) biopsies have failed to provide definitive guidance on nodule malignancy, the Afirma genomic-sequencing-classifier RNA test and the ThyroSeq v3 multigene-genomic-classifier DNA-RNA test are similarly predictive, according to researchers in California.

As Dr. Masha Livhits of the David Geffen School of Medicine at UCLA, in Los Angeles, told Reuters Health by email, "Our findings suggest that either molecular test can be used to refine the diagnosis of indeterminate thyroid nodules - those with uncertain biopsy results."

"The main clinical benefit," she added, "is that approximately half of patients with indeterminate thyroid nodules who undergo molecular testing are able to avoid surgery on the basis of a negative molecular test result."

About 20% of patients who undergo FNA biopsies have nodules with indeterminate cytology, Dr. Livhits and colleagues note in JAMA Oncology. The risk of malignancy in such circumstances may be as high as 40%, they add.

To determine the efficacy of molecular testing, the researchers examined data on more than 2,300 patients and established that 397 had indeterminate nodules. After exclusions, primarily because of concurrent biopsy of an additional nodule with malignant cytology or clinician preference, the researchers randomized 346 patients with 372 nodules to RNA or DNA-RNA testing. The participants' median age was 55 and about two-thirds were women.

The tests, which according to the researchers are the best-validated current molecular tests for the diagnosis of indeterminate thyroid nodules, demonstrated sensitivities ranging from 97% to 100% and "reasonably high" specificities of 80% to 85%.

The proportion determined to be benign via the RNA test (53%) was not significantly different from that of the DNA-RNA test (61%). The researchers also found that compared with an earlier version of the RNA-DNA test (ThyroSeq v2) there was no significant difference in positive predictive values.

However, compared with a prior version of the RNA test, the current version showed increased positive predictive values.

Diagnostic thyroidectomy was avoided in 87 (51%) patients given the RNA test and 83 (49%) who had the DNA-RNA test. Of the 90 nodules for which surveillance ultrasonography was available, 85 (94%) remained stable over a median follow-up of 12 months.

In light of their equivalent performance, the researchers conclude that "the choice of molecular test may hinge on factors other than diagnostic performance, such as cost, processing time, sample inadequacy rate, and information regarding specific mutations that may guide future treatment."

Dr. Jonathon O. Russell, director of endoscopic and robotic thyroid and parathyroid surgery at Johns Hopkins Medicine, in Baltimore, Maryland, said the study, like others before it, supports "the progress of molecular markers in the management of thyroid nodules. Using these markers, the authors were able to reduce the need for diagnostic thyroid surgery by about 50%. In a time when we are over-treating many thyroid nodules, it is valuable to know which patients can safely avoid surgery."

"It is important to remember that many patients will have a desire for surgery due to anxiety or symptoms that a thyroid nodule is causing," he told Reuters Health by email. "In those situations, these tests may not add value to the care of patients and should not always be ordered."

Dr. Russell concluded, "It is also important to remember that these tests are only one element of the patient decision-making process. Finding a multi-disciplinary team that can help a patient determine an individualized thyroid nodule treatment plan remains critical."

The study did not have commercial funding.

SOURCE: https://bit.ly/2K4gvMK JAMA Oncology, online December 10, 2020.

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