Genetic test helps avoid needless thyroid surgery

Jul 10 2012

By Lauretta Ihonor

US researchers report that a gene-based test may help to identify patients who have cytologically indeterminate thyroid nodules that are benign.

As all patients with cytologically indeterminate thyroid nodules are referred for surgery, the use of this test may ensure that only patients with malignant nodules undergo surgery, say the investigators.

The surgical removal of thyroid nodules is known to cause complications in up to 10% of patients who have the procedure. Exposing patients with benign nodules to the risk for surgery should be avoided, explain Erik Alexander (Brigham and Women's Hospital, Boston, Massachusetts) and team.

The researchers recruited 3789 patients with thyroid nodules who underwent fine needle aspirations (FNAs) on thyroid nodules with a diameter of at least 1 cm.

A total of 4812 FNA samples were taken, of which 577 were cytologically indeterminate. In all, 265 of these indeterminate samples were included in the final analysis.

A histopathologic review revealed that 85 of these samples were malignant.

This, say Alexander and team, suggests that 68% of nodules may be resected unnecessarily.

When a gene-expression microarray assay was used to test all 265 indeterminate samples, 78 of the 85 malignant samples were correctly identified as malignant, reflecting a test sensitivity of 92%.

Investigation showed that six of the seven malignant samples incorrectly identified showed a low gene-expression level.

"This finding suggests that assay failure is not responsible for the six false negative cases," say Alexander and co-investigators in TheNew England Journal of Medicine.

Further assessment of the test's accuracy revealed a specificity of 52%.

In an accompanying editorial, J Larry Jameson (University of Pennsylvania, Philadelphia, USA) wrote: "This test does not have sufficient specificity to inform decision making for samples with clear-cut cytologic results (ie, benign or malignant)."

Nonetheless, he concluded that the gene-expression test may be useful for reducing unnecessary thyroid surgery.

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