Sonographic Pattern Stratifies Thyroid Nodule Malignancy Risk

NASHVILLE, Tenn. — Clinicians should use sonographic pattern to set the threshold for thyroid nodule biopsy, and to stratify the risk for malignancy to guide management after biopsy, according to a retrospective study presented at the American Association of Clinical Endocrinologists (AACE) 24th Annual Scientific & Clinical Congress.

In the study, researchers looked at thyroid nodules with indeterminate cytology and histological confirmation and found that sonographic patterns were adequate to determine diagnostic surgery.

 “The rationale for the study in the first place was how to deal with the indeterminate cases. It has been a challenge for decades and it happens in 20% to 30% of the biopsies we do,” said study investigator Bryan McIver, MD, who is in the division of Endocrine Oncology at the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Florida. 

“This has led to the development of high technology in the molecular marker field. It is a really hot topic, and the commercial offerings claim they can give you specific valuations. We think we can look at the ultrasound pattern and use the new groupings and apply that to the samples.”

The provisional 2014 revised American Thyroid Association (ATA) guidelines for the management of thyroid nodules recommends using a classification based on the sonographic appearance of the nodules to determine whether a biopsy is warranted. Each pattern is associated with an estimated risk for malignancy and a different size threshold for biopsy.

McIver and his colleagues reviewed the charts of all patients with cytological evaluation at a single institution between October 2008 and May 2014. In their review, the investigators only included those nodules with indeterminate cytology (Bethesda categories III and IV) and histological confirmation that had ultrasound images available for review. 

The review included 432 thyroid nodules, 367 (85%) of which had indeterminate cytology and histological confirmation.

The overall risk for malignancy was 30.8% in this cohort, and cytology classified 147 nodules (40%) as atypia of undetermined significance (AUS) and 220 (60%) as follicular neoplasm (FN), according to the data. The overall risk for malignancy for the AUS category was 28.6%, and it was 32.3% for the FN category.

The researchers found the sonographic suspicion pattern was “very low” in 27 nodules (7.4%), “low” in 170 (46.3%), “intermediate” in 36 (9.8%) and “high” in 134 (36.5%), according to the ATA classification. The ROM for the “very low” category was 3.7% and the ROM for the “low” category was 25.3%. The risk for malignancy for the “intermediate” category was 22.2% and 45.5% for the “high” category.

The study demonstrated no significant differences in the risk for malignancy of nodules with cytological diagnosis of AUS or FN in each category. The researchers also reported that there were no significant differences in the risk for malignancy between the “low” and “intermediate” suspicion patterns. 

However, there were statistically significant differences in the risk for malignancy when the “low-intermediate” suspicion pattern was compared with the “very low” suspicion pattern and with the “high” suspicion pattern. 

The researchers concluded that ultrasound images effectively stratify the risk for malignancy of nodules with indeterminate cytology and surgery could be avoided in nodules with a “very low” suspicion sonographic pattern. The negative predictive value was 96%. 

 “The intermediate groups are the ones who might benefit from the molecular marker studies. They have 20% to 25% of chance and then you apply the molecular marker panels and you can get a better picture of overall disease risk,” McIver said in an interview with Endocrinology Advisor. “We can avoid the need for the molecular marker in 40% of cases. So, that will save money for the healthcare system, and it gives us a more accurate use from these molecular markers.”

Reference

1. Valderrabano P et al. Abstract #1003. Presented at: American Association of Clinical Endocrinologists (AACE) 24th Annual Scientific & Clinical Congress; May 13-17, 2015; Nashville, Tenn.