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Ultrasound characteristics may predict thyroid cancer risk
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Three ultrasound diagnostic characteristics may help predict which thyroid nodules are cancerous and thereby reduce the number of unnecessary biopsies, according to results of a retrospective, case-control study.
“Uncertainty about which nodules may harbor cancer and lack of evidence-based management guidelines have resulted in a myriad of conflicting recommendations regarding which nodules warrant biopsy, frequent thyroid biopsies, and the overdiagnosis of thyroid cancers that would otherwise likely have remained asymptomatic in the absence of detection,” Rebecca Smith-Bindman, MD, of the University of California, San Francisco, and colleagues wrote.
Rebecca Smith-Bindman
The analysis included 8,806 patients who underwent 11,618 thyroid ultrasound examinations from January 2000 to March 2005. Of these patients, 105 were diagnosed with thyroid cancer.
Researchers noted that thyroid nodules were common in patients diagnosed with cancer (96.9%), as well as those without a diagnosis of thyroid cancer (56.4%).
Results linked the following three ultrasound characteristics with thyroid cancer: microcalcifications (OR=8.1; 95% CI, 3.8-17.3); size >2 cm (OR=3.6; 95% CI, 1.7-7.6); and entirely solid composition (OR=4.0; 95% CI, 1.7-9.2).
According to these findings, using one characteristic as an indication for biopsy would detect most thyroid cancer cases, with a sensitivity of 0.88 (95% CI, 0.80-0.94). However, the false-positive rate would be high (0.44; 95% CI, 0.43-0.45) and the positive likelihood ratio (2.0; 95% CI, 1.8-2.2) would be low. Additionally, 56 biopsies would be performed per cancer diagnosed.
Use of two characteristics for biopsy would translate to a sensitivity of 0.52 (95% CI, 0.42-0.62); false-positive rate of 0.07 (95% CI, 0.07-0.08); and positive likelihood ratio of 7.1 (95% CI, 6.2-8.2), researchers wrote. Only 16 biopsies would be performed per cancer diagnosed.
Researchers suggested implementation of a more stringent approach would result in a 90% decrease in unnecessary biopsies while maintaining a low risk for cancer, as compared with the current approach of performing biopsies of all thyroid nodules >5 mm.
“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. “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.”