ACR White Paper Aims to Cut Thyroid-Nodule Workups

Miriam E Tucker

November 12, 2014

The American College of Radiology (ACR) has issued a new white paper aimed at reducing the number of incidentally discovered thyroid nodules referred for further workup. But the paper is generating some controversy, because it leaves the issue of whether to report small thyroid nodules seen on scans to the discretion of the radiologist.

The clinical conundrum of the thyroid nodule discovered incidentally when a patient receives neck imaging for another purpose is important for three reasons, lead author of the white paper, Dr Jenny K Hoang (Duke University Medical Center, Durham, North Carolina), told Medscape Medical News.

"First, the incidental thyroid nodule is a very common finding on imaging studies, and a majority of thyroid nodules are benign. Second, the workup has led to increased costs from additional procedures and in some cases to increased risk to the patient from unnecessary surgery. Third, small incidental thyroid malignancies typically have indolent behavior. Given these three facts, many incidental thyroid nodules that radiologists currently report should not receive workup," she said.

The paper was published online November 1, 2014 in the Journal of the American College of Radiology by Dr Hoang and colleagues.

But Dr David S Cooper (Johns Hopkins University School of Medicine, Baltimore, Maryland) questions whether clinicians would be willing to follow the ACR's approach, which would result in a large proportion of incidentally discovered nodules receiving no workup or follow-up.

"The radiologists are the ones initiating the process of incidental thyroid nodule discovery. Therefore, this is a great effort on their part to try to do something to stop the flood of imaging that leads to more and more people having procedures. However, I just don't think what they're saying is going to be very practical," Dr Cooper, lead author of the American Thyroid Association 2009 thyroid-nodule management guidelines, told Medscape Medical News.

Which Nodules Are Worrisome?

The white paper is not to be construed as "guidelines" because it does not represent official ACR policy and should not be interpreted as a legal standard of care, the authors note.

But, says Dr Hoang, it "provides recommendations to guide radiologists in reporting incidental thyroid nodules. The two main benefits are a reduction in the number of thyroid nodules reported by radiologists and greater consistency in the way radiologists report the nodules."

The document provides separate flowcharts for nodules identified by computed tomography (CT) or MRI and those found on fluorodeoxyglucose–positron emission tomography (FDG-PET) or other nuclear-medicine scans.

Because nodules with focal uptake on FDG-PET scans carry a high (33%-35%) likelihood of malignancy, the white paper advises ultrasound follow-up for all such nodules found in individuals with normal life expectancy.

However, for nodules detected by CT or MRI that have no additional suspicious findings (such as lymph-node abnormalities or local invasion), the algorithm advises ultrasound follow-up only for patients aged 35 and older with nodules of 1.5 cm or larger and for those aged 35 years or younger with nodules 1 cm or larger.

No further evaluation is recommended for nodules less than 1.5 cm in patients aged 35 and older, nodules less than 1 cm in patients less than 35 years old, or in any patient with limited life expectancy.

Dr Hoang told Medscape Medical News that this approach is based on a "three-tiered system" for categorizing incidental thyroid nodules that she developed after reviewing the literature and then performing several studies in different cohorts to validate the system.

One of those studies compared the three-tiered system with a commonly used 1-cm size cutoff for patients with thyroid cancers in the Surveillance, Epidemiology, and End Results database of the US National Cancer Institute and found no difference in cancer capture rate and no difference in survival outcomes (AJNR Am J Neuroradiol. 2013; DOI:10.3174/ajnr.A3487).

In a second paper, Dr. Hoang and colleagues applied the approach to a database of surgically treated malignancies over a 10-year period and found that potentially missed malignancies represented only 1.2% of all thyroid malignancies. Moreover, all of those that would have been missed were small and less aggressive (Thyroid. 2014; DOI:10.1089/thy.2014.0066).

Nonetheless, Dr Cooper told Medscape Medical News, "I don't think clinicians will be willing to refrain from ordering an ultrasound if a 1.3-cm nodule is discovered in a 37-year-old woman."

He also questioned whether the age and size cutoffs are supported by data. "I don't think there's a lot of evidence for the arbitrary division at age 35 or 1.5 cm for further evaluation," he told Medscape Medical News.

And he expressed another concern: "There are no provisions made for follow-up of the patient once a thyroid nodule has been incidentally discovered."

Radiologists Decide Whether to Mention Nodules, and Where

Dr Hoang told Medscape Medical News, "Radiologists see incidental thyroid nodules commonly. Studies find the prevalence to be 16% to 25% of CT scans and up to 67% of ultrasound exams. Given the low malignancy rate in these nodules and indolent behavior of small thyroid malignancies, the committee does not recommend workup or follow-up with ultrasound in all thyroid nodules, especially small thyroid nodules."

The ACR committee advises radiologists against reporting the existence of nodules that don't meet the criteria for further evaluation in the impression/conclusion section of the radiology report that is sent back to the ordering physician and leaves the decision of whether to mention it in the body of the report to the discretion of the individual radiologist.

Dr Cooper told Medscape Medical News, "I think that it is inappropriate and paternalistic for a radiologist to observe an incidentally discovered thyroid nodule and then not mention it at all in the impression [section] or even in the body of the report. I realize they think that they may be doing the right thing by decreasing unnecessary testing, but this is not their decision to make."

ATA president Dr Hossein Gharib (Mayo Clinic College of Medicine, Rochester, Minnesota) agrees: "I think the report should mention the nodule and leave up to the clinician to decide what to do next. Omission could be confusing and possibly unethical."

Comparison With Other Recommendations

The ACR white paper approach contrasts with the 2009 ATA thyroid-nodule and thyroid-cancer guidelines, which recommend ultrasound imaging for all incidentally discovered thyroid nodules. Following this, the sonographic characteristics of the nodule are then used to determine whether a biopsy is needed.

Dr Cooper told Medscape Medical News, "We have ample evidence to support this approach. If the nodule looks benign on ultrasound, you don't need to do anything more. But the ATA says you do need to do the ultrasound."

Also in contrast to the ACR approach, the ATA recommends follow-up for those nodules that are not biopsied, at 24 months for those deemed low risk on ultrasound and in 12 to 24 months for those with intermediate risk on ultrasound.

The ATA guidelines are currently under revision, but the new document, due out in early 2015, will not change with regard to this issue, Dr Cooper told Medscape Medical News.

The American Association of Clinical Endocrinologists' guidelines, issued jointly with the Associazione Medici Endocrinologi and the European Thyroid Association, advise that ultrasound be performed for all palpable nodules and also for patients in whom a thyroid disorder is suspected based on clinical grounds or risk factors, including history of head/neck irradiation, family history of thyroid cancer, male sex, and age less than 14 years or greater than 70 years.

Those guidelines are also being revised and will be released in 2015, Dr Gharib told Medscape Medical News.

Dr Hoang and coauthors report no relevant financial relationships, as do Dr Cooper and Dr Gharib.

J Am Coll Radiol. Published online November 1, 2014. Abstract

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