CHICAGO — As the prevalence of thyroid nodules diagnosed on ultrasound increases, clinicians trying to decide whether to biopsy a particular nodule should consider adding a serum TSH test to their work-up, Dr. R. Brooke Jeffrey Jr. said at the annual meeting of the Radiological Society of North America.
At the moment, “what is driving our approach to thyroid diagnosis is money and patient hysteria,” said Dr. Jeffrey of the department of radiology at Stanford (Calif.) University. In addition, the lack of clinical findings that indicate with certainty which nodules are more likely to be malignant contributes to a high biopsy rate.
Deciding which patients to biopsy is “a very contentious issue,” he added, noting that different medical societies have issued conflicting guidelines. Though thyroid nodules are commonly detected, few thyroid cancers are diagnosed. But clinicians do not want to miss a cancer diagnosis, and thyroid biopsies can be lucrative.
A recent review indicated that thyroid cancer mortality has not changed in 30 years, despite the increased incidence of thyroid cancer, a result Dr. Jeffrey attributed to overdiagnosis (JAMA 2006;295:2164–7).
He also concluded that ultrasound, which has become much more widely available in the past 30 years, has not contributed to a decrease in mortality. Ultrasound gives information about many features of thyroid cancer, such as whether a mass is solid, hypoechoic, taller than it is wide, and whether it has microcalcifications and irregular margins. But because no single feature has a high sensitivity and specificity, clinicians cannot rely on ultrasound to rule out cancer, so they order biopsies.
However, recent data indicated that patients with clinically detected goiters and high normal TSH values had a higher incidence of thyroid cancer (J. Clin. Endocrinol. Metab. 2006;91:4295–301). By “combining ultrasound features and laboratory values, we might be able to come up with an algorithm,” Dr. Jeffrey said.
Even if TSH levels prove useful, clinicians will still confront difficult issues when deciding whether to biopsy thyroid nodules: how long to track the nodules before biopsy and what sort of interval growth might indicate a benign or a worrisome condition.