Nodule Size Should Not Determine Biopsy Decision in Thyroid Cancer

Muhammad Anwar, MBBS

The recent American Thyroid Association (ATA) guidelines to abstain from cytological evaluation by biopsy for patients with thyroid cancer on the basis of having thyroid nodules ≤1 cm is not advisable, according to Muhammad Anwar, MBBS.

Anwar presented a retrospective analysis at the 2015 International Thyroid Congress indicating that thyroid nodule size alone is insufficient information for making a biopsy decision, as he and his colleagues found that prognosis and risk of cancer recurrence are independent of thyroid nodule size at presentation.

“Based on our data we conclude that the risk for occurrence in the sub-centimeter nodules is the same as for larger nodules,” said Anwar, who is in the Department of Surgery at Tulane University School of Medicine. “The current question is to identify another tool that can be used to better determine the future prognosis for any size nodule. Until we can identify a tool that can be used to better determine the true malignancy risk, we believe we should continue to biopsy subcentimeter nodules under the 2009 guidelines.”

The ATA guideline recommends that cytological biopsy should not be performed for patients with thyroid nodules that are ≤1 cm. However, analysis of evidence-based data examining whether or not >1-cm thyroid nodules indicate a higher risk of recurrence and malignancy is lacking.

To address this question, Anwar and co-investigators at Tulane, performed a retrospective analysis, spanning 6 years, of patients with thyroid nodules of various sizes. They identified 912 nodules for analysis. Roughly 17% (n = 154) were malignant and 83% (n = 758) were benign. Based on the ATA risk score criteria, there were 5% (n = 8) in the high-risk, 20% (n = 31) in the ATA intermediate-risk, and 74% (n = 114) in the ATA low-risk categories.

For prognostic outcomes, each patient was also stratified to three categories based on MACIS scores (distant Metastasis, patient Age, Completeness of resection, local Invasion, and tumor Size), which are used to predict mortality for papillary thyroid carcinoma in adults. The rate of cancer recurrence and outcome for patients was analyzed with respect to whether the thyroid nodule is ≤1 cm compared with >1 cm and evaluated with respect to malignant potential and outcome.

The data presented at the meeting showed that there was no significant difference in the ATA risk of recurrence for patients initially presenting with ≤1-cm lesions compared with >1 cm (P = .72). Similarly, the size of the initial presenting thyroid nodule was not predictive of MACIS probability outcome (P = .76). There was no significant difference between initial presentations of ≤1-cm compared to >1-cm nodules. This suggests that larger thyroid nodule size is not suggestive of a poor prognosis.

Analysis of the prognostic indicators other than nodule size confirmed that calcifications detected by ultrasound, extrathyroid extensions, capsular invasion, lymphovascular invasion, aggressive histology, BRAF mutation, and positive surgical margins were all directly associated with higher risk of disease recurrence and of poorer prognosis. Of the 13 malignant cases with nodule size ≤1 cm, there were 2 that had extrathyroid extension. Two more had capsular invasion. Five had lymphovascular invasion and 6 had positive BRAF mutation (P >.05).

The investigators noted that prospective studies are needed to confirm their findings.

Anwar M, Alshehri M, Murad F, et al. Do the recent American Thyroid Association guidelines accurately guide the biopsy according to nodule size? A retrospective review. Presented at: 2015 International Thyroid Congress; October 18-23, 2015; Orlando, FL. Abstract 470.

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