Thyroid ultrasound imaging could be used to identify patients who have a low risk of thyroid cancer for whom biopsy could be deferred, according to a retrospective case-control study reported in JAMA Internal Medicine. Reviewing 11,618 thyroid ultrasound imaging examinations from 8,806 patients identified 105 patients diagnosed as having thyroid cancer. “Thyroid nodules were common in patients diagnosed as having cancer (96.9%) and patients not having cancer (56.4%),” the researchers noted.
The only findings associated with the risk of thyroid cancer were three nodule characteristics seen on ultrasound—microcalcifications (odds ratio = 8.1), size greater than 2 cm (odds ratio = 3.6), and an entirely solid composition (odds ratio = 4.0). Requiring two of these abnormal nodule characteristics to prompt biopsy, rather than performing biopsy for all thyroid nodules larger than 5 mm, would reduce unnecessary biopsies by 90% while maintaining a low risk of cancer (5 per 1,000 patients for whom cancer is deferred), according to the investigators.
“Although thyroid nodules are common, most (98.4%) are benign, highlighting the importance of being prudent in deciding which nodules should be sampled to reduce unnecessary biopsies,” the researchers wrote. They concluded that “adoption of uniform standards for the interpretation of thyroid sonograms would be a first step toward standardizing the diagnosis and treatment of thyroid cancer and limiting unnecessary diagnostic testing and treatment.”
An invited commentary accompanying the study argued that some aspects of the single-institution design may have resulted in a nonrepresentative study population, and “notwithstanding the high-quality nature of the author’s sonographic review and data analysis, the study’s epidemiologic interpretations are not readily transferrable to clinical practice.”
This does not imply, however, that the study’s “conceptual framework should not be applied to thyroid nodule evaluation,” they continued. “Sonographic features are, and should remain, the principal tool to guide thyroid cancer risk assessment. Solid nodules larger than 1 cm, especially with microcalcifications, should be the primary focus of diagnostic evaluation.” ■
Smith-Bindman R, et al: JAMA Intern Med. August 26, 2013 (early release online).
Alexander EK, Cooper D: JAMA Intern Med. August 26, 2013 (early release online).