Ultrasound Criteria May Allow for More Selective Thyroid Biopsies
Ultrasound criteria may help determine when a thyroid nodule should be biopsied and help reduce the number of unnecessary procedures, according to a retrospective case-control study in JAMA Internal Medicine.
Current guidelines recommend biopsy of many thyroid nodules >5 to 15 mm in diameter. However, the new findings suggest the presence of two of three abnormal characteristics found on ultrasound may further refine the decision for biopsy.
“Compared with other existing guidelines, many of which are complicated to apply, following these simple, evidence-based guidelines would substantially decrease the number of unnecessary thyroid biopsies in the United States,” said lead author Rebecca Smith-Bindman, MD, Professor, Department of Radiology and Biomedical Imaging, University of California San Francisco School of Medicine. “Right now, we’re doing far too many thyroid biopsies in patients who are really at very low risk of having thyroid cancer,” she said.
“These important data support many of our guidelines,” commented Erik K. Alexander, MD, Associate Professor of Medicine, Harvard Medical School, and Physician, Brigham and Women's Hospital, Boston, Mass, and member of the Board of Directors for the American Thyroid Association. “However, we also don’t want to create a blanket statement that we need to perform or avoid a biopsy of all nodules simply based upon their size, or any exacting ultrasound features. Rather, we are seeking to really find the balance inclusive of all of the clinical data. That is the key.”
“Ultrasound is by far the best way to evaluate the thyroid,” Dr. Alexander said. “For every patient, we want to use historical data and physical examination, ultrasound and imaging data, while also recognizing that fine needle aspiration is an extremely low risk, minimally invasive procedure that can provide a lot of very useful information,” he said.
Large Study of More than 8,800 Patient Records
The authors examined medical records from 8,806 patients who underwent 11,618 thyroid ultrasound examinations from January 2000 to March 2005. Of this group, 105 patients were diagnosed with thyroid cancer.
While thyroid nodules >5 mm were found in almost all patients with thyroid cancer (96.9%), they were also found in over half (56.4%) of patients without thyroid cancer. The authors identified three characteristics of nodules found on ultrasound that were significant predictors of thyroid cancer—microcalcifications (odds ratio [OR] 8.1), size >2 cm (OR, 3.6), and an entirely solid composition (OR, 4.0).
New Criteria Would Reduce Unnecessary Biopsies by 90%
Using a requirement that nodules have at least two of these three abnormal characteristics would reduce the number of unnecessary biopsies by 90% with a low risk of cancer in patients who do not undergo biopsy (ie, 5 cancers [0.5%] per 1,000 ultrasound examinations), according to the authors.
“If there’s a large solid nodule, or if there are any nodules with microcalcification, the likelihood of cancer increases by fivefold or tenfold, depending on the finding, and I would do a biopsy,” said Dr. Smith-Bindman. “On the other hand, without these characteristics, you are at very low risk—less than one-half of 1%—and a biopsy is not necessary. Nor is continued surveillance,” she said.
Clinical Implications of the Findings
“The principle of using ultrasound characteristics and guidance for helping to risk stratify is critical, and I think the principles that the authors lay out support what is the accepted standard among national and international guidelines,” Dr. Alexander said.
However, the findings should be interpreted with caution as there were study limitations. For example, the incidence of thyroid cancer in patients with thyroid nodules is typically 8% to 15%, but is <2% in this study, he said. It is also unclear if ultrasound-guidance was used for all nodule biopsies. “It doesn’t take away from their findings, but we want to be thoughtful and cautious in terms of how we translate those findings into a change in clinical practice,” Dr. Alexander said.
Smith-Bindman R, Lebda P, Feldstein VA, et al. Risk of thyroid cancer based on thyroid ultrasound imaging characteristics: results of a population-based study. JAMA Intern Med. 2013;173(19):1788-1796.