Thyroid Ultrasound May Identify Cancer in Low-Risk Patients

Ultrasound imaging of the thyroid could be used to identify patients at low risk of cancer for whom biopsy could be deferred, according to a study published in JAMA Internal Medicine.

Researchers from the University of California, San Francisco and the Cleveland Clinic in Ohio sought to quantify the risk of thyroid cancer-associated thyroid nodules based on ultrasound imaging characteristics. They undertook a retrospective case-control study of 8,806 patients who underwent 11,618 thyroid ultrasound examinations from January 1, 2000, to March 30, 2005.

The results showed that 105 of the patients were subsequently diagnosed with thyroid cancer. Thyroid nodules were present in 96.9 percent of the patients with thyroid cancer and in 56.4 percent of those who did not have cancer.

The nodules were found to have three characteristics associated with the risk of thyroid cancer:

·         Microcalcifications

·         Be larger than 2 cm

·         Entirely solid composition

The researchers noted that if clinicians used only one of the characteristics to indicate a biopsy, most thyroid cancer cases would be detected, but there would be a high false-positive rate and a low positive-likelihood ration. For every cancer diagnosis, there would be 56 biopsies. If clinicians used two characteristics for a biopsy, both sensitivity and false-positive rates would be lower, and the positive likelihood would be higher. For every cancer diagnosed, there would be 16 biopsies.

“Compared with performing biopsy of all thyroid nodules larger than 5 mm, adoption of this more stringent rule requiring two abnormal nodule characteristics to prompt biopsy would reduce unnecessary biopsies by 90 percent while maintaining a low risk of cancer (five per 1,000 patients for whom biopsy is deferred),” the authors wrote.

The authors concluded that although more study is needed to validate their findings, thyroid ultrasound imaging could be useful in identifying low-risk patients who may have thyroid cancer.