It’s Usually Not Thyroid Cancer

Thyroid nodules could be assessed with ultrasound instead of biopsies

(RxWiki News) You could have a lump on your thyroid and not even know it. More than half of adult Americans have lumps — called nodules — on the thyroid, a gland at the base of the neck. There’s controversy about which of these nodules need to be tested for cancer.

A new study suggests that ultrasound imaging (sound waves used to produce pictures) could be used to assess low-risk thyroid nodules.

The study also defined nodule characteristics that could be used to determine when a lump should be biopsied, a procedure in which a tissue sample is taken to test for the presence of cancer.

A more selective approach to thyroid nodule testing, along with standardized guidelines for interpreting ultrasound results, could prevent patients from undergoing unnecessary invasive procedures, according to the study's authors.

"Find out the purpose of all medical tests you undergo."

Rebecca Smith-Bindman, MD, in the Department of Radiology and Biomedical Imaging at University of California, San Francisco, led this study that reviewed data on 8,806 patients who had 11,618 thyroid ultrasound imaging examinations from January 2000 through March 2005.

A total of 105 (1.2 percent) study participants were diagnosed with thyroid cancer.

The researchers found that nodules were discovered in most (96.9 percent) of the patients diagnosed with cancer and 56.4 percent of patients who did not have cancer.

“Although thyroid nodules are common, most (98.4 percent) are benign, highlighting the importance of being prudent in deciding which nodules should be sampled to reduce unnecessary biopsies,” the authors wrote.

The research team found that several nodule characteristics were associated with a greater likelihood of cancer:

  • Nodules that had specks of calcium (microcalcifications) were eight times more likely to be cancer than nodules without these flecks.
  • Nodules larger than 2 centimeters (just over three quarters of an inch) had a 3.6-fold higher likelihood of being cancer than smaller lumps.
  • Nodules that were solid were four times more likely to be cancer than those that were filled with fluid.

The authors suggest that at least two of these characteristics should be present before a biopsy is performed. Using this approach could not only accurately diagnose most thyroid cancers, but decrease the amount of unnecessary testing.

“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 (5 per 1,000 patients for whom biopsy is deferred),” the authors wrote.

“Thyroid ultrasound imaging could be used to identify patients who have a low risk of cancer for whom biopsy could be deferred. On the basis of these results, these findings should be validated in a large prospective cohort,” the authors wrote.

dailyRx News spoke with  D. Gregory Farwell, MD, FACS, director of Head and Neck Oncology and Microvascular Surgery at the University of California, Davis, about this research. He is concerned that there are no pathology reports confirming the data presented.

"They [researchers] rely on a database catching all patients who underwent thyroid ultrasound who ultimately develop thyroid cancer. This is problematic for a couple of reasons," Dr. Farwell said.

"One is that it is possible some patients leave the state or are missed in the database. Secondly, and most importantly, is that they did not perform a biopsy or  thyroidectomy [removal of thyroid] and confirm with pathology the ultrasound findings."

"Most well-differentiated thyroid cancers develop slowly," Dr. Farwell continued, "and it is very possible that should the researchers follow their cohort longer, there will be additional cancers that develop in those patients."

"This paper provides some provocative and intriguing guidelines and is a step towards minimizing unnecessary biopsies in patients with thyroid nodules.  However, until we have better long term data to predict which thyroid cancers are going to behave aggressively, early diagnosis and management is still the standard of care," Dr. Farwell concluded.

Findings from this study were published August 26 in JAMA Internal Medicine.

The study was supported by grants from the National Cancer Institute and a SEED grant from the Department of Radiology and Biomedical Engineering, University of California, San Francisco. No conflicts of interest were disclosed.

Review Date: 
August 26, 2013