AT WCTC 2017

BOSTON (FRONTLINE MEDICAL NEWS) – Normalizing the serum thyroglobulin level by thyroid nodule size in patients surgically treated for a thyroid nodule produced a strongly significant link between the level of this marker and nodule malignancy in a review of nearly 200 patients treated at any of three Montreal centers.

After normalization, the serum thyroglobulin of patients with a malignant nodule averaged 51 mcg/L*cm, more than double the average 23 mcg/L*cm among patients with benign nodules, Neil Verma, MD, said at the World Congress on Thyroid Cancer.

Incorporation of normalized serum thyroglobulin level into the McGill Thyroid Nodule Score Plus ( MTNS+ ) could improve the score’s predictive accuracy, said Dr. Verma, who is now a researcher at the University of Toronto but performed his analysis while at McGill University in Montreal. Normalization by size makes the serum thyroglobulin level more reflective of the nodule’s activity, he explained. The MTNS+ already includes non–normalized serum thyroglobulin as a component: It is 1 of the 23 risk factors for thyroid cancer used to calculate the MTNS+ ( Thyroid. 2014 May 19;24[5]:852-7 ).

But the senior investigator on the study said that, even if the MTNS+ gets a little more accurate by using a nodule size-normalized serum thyroglobulin level, the clinical utility of the MTNS+ will soon be completely eclipsed by widespread reliance on molecular tests, whereas the MTNS+ combines many clinical and conventional laboratory measures. It‘s only a matter of cost, said Richard J. Payne, MD , a head and neck surgeon at McGill.

The MTNS+ “is a cheap version of molecular testing,” Dr. Payne said in an interview. “I believe the MTNS+ will be outdated within 5 years – once molecular testing becomes cheaper” than it is now. He estimated that currently, at his institution, the cost for molecular testing of a single thyroid nodule runs between $1,000-$5,000 Canadian dollars (about $800-$4,000 U.S.). Furthermore, it is not routinely covered by Canadian provincial medical payers at this time, he said. A small number of his patients opt to pay for molecular testing themselves.

Routine reimbursement for molecular diagnostic tests for the malignancy of thyroid nodules was discussed at a recent meeting of Canadian head and neck surgeons, who decided to lobby provincial governments to try to get it covered, according to Dr. Payne. “I’d be very surprised if we don’t have government coverage within 4-5 years,” in part because the cost for molecular testing will likely fall significantly in that time frame, he predicted.

The analysis reported by Dr. Verma included 196 patients with thyroid nodules who underwent a partial or total thyroidectomy at any of three McGill teaching hospitals during 2010-2015. He determined the benign or malignant status of their nodules based on their histology. The analysis he presented also showed that malignancy had no clear relationship to nodule size. Nodules that were less than 2 cm in diameter were about as likely to be malignant as were those that were 3 cm or larger in diameter, Dr. Verma reported .

Size-normalized serum thyroglobulin will now be incorporated into the MTNS+, which will be the fourth change to the original MTNS scoring system since it was developed more than a decade ago, noted Dr. Payne. But, while the MTNS+ allows better prediction of malignant potential than does the Bethesda system for evaluating nodule cytopathology in a fine-needle aspirate, it still falls short of molecular testing in its predictive accuracy, Dr. Payne said.

Dr. Verma and Dr. Payne had no disclosures.

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