甲状腺癌 超声

No single ultrasound feature can predict malignancy in thyroid nodules with acceptable diagnostic accuracy, a new systematic review and meta-analysis suggest.

The findings have beenpublished online for open accessinThyroidby Luciana Reck Remonti, MD, an endocrinologist at Hospital de Clinicas de Porto Alegre, Brazil, and colleagues.

"Our meta-analysis evaluated the accuracy of ultrasound in predicting thyroid-nodule malignancy using the appropriate gold standard: histopathological diagnosis. Based on our results, no single ultrasound characteristic is accurate in diagnosing thyroid malignancy," Dr Remonti toldMedscape Medical News.

Nonetheless, she said that ultrasound is still important for the evaluation of thyroid nodules. Although fine-needle aspiration (FNA) biopsy is considered the most accurate procedure to identify malignant nodules, to implement biopsies in all patients harboring a thyroid nodule "is too burdensome," she and her colleagues note.

So "we need to be able to better select which patients need to be submitted to [FNA biopsy]," Dr Remonti said.

"Probably, the aggregation of ultrasound characteristics will be able to better define patients with nodules at risk," she noted, recommending that a "risk score" for thyroid malignancy, based on a number of features seen on ultrasound, be developed in the future.

Asked to comment, Stephanie L Lee, MD, PhD, associate professor of medicine and director of the Thyroid Health Clinic at Boston University Medical Center, Massachusetts, toldMedscape Medical Newsthat these findings essentially confirm what is known and are in line with both the current (2009) American Thyroid Association (ATA) guidelines on thyroid nodules, as well as new ATA guidelines due out this year. (Dr Lee was on the ATA writing committee for the 2009 guidelines and the prior ones, and although she is not an author on the 2015 guidelines, she has seen them.)

Essentially, Dr Lee said that the ATA approach is "if it looks worrisome — invasion outside the thyroid, unilateral adenopathy — you should biopsy all nodules." In contrast, if a nodule is simply hypoechoic, isoechoic, or spongiform, biopsy should be considered only if it reaches a certain size. "So, it's a risk stratification."

Which Ultrasound Features, if Any, Predict Cancer?

Dr Remonti and colleagues analyzed 52 observational studies of patients with a total 12,786 thyroid nodules that had been evaluated by ultrasound and submitted to thyroidectomy and for which histological diagnosis of surgical specimens was conducted.

They also performed a separate meta-analysis on nine studies that included 1851 nodules with indeterminate cytology aspirates.

All the features they evaluated — solid structure, hypoechogenicity, irregular margins, absence of halo, microcalcifications, central vascularization, solitary nodule, heterogeneity, taller-than-wide shape, and absence of elasticity — were significantly associated with malignancy.

However, the sensitivity of these features was somewhat low, ranging from 26.7% to 63%. Thus, using these features individually would result in 37% to 73.3% of cancers being missed, the authors explain.

The features with the best specificity were microcalcifications (87.8%), central vascularization (78%), irregular margins (83.1%), and a taller-than-wide shape (96.6%).

The positive likelihood ratio (ie, how many times more frequently patients with malignancy present with that particular result than does a patient without malignancy) ranged from 1.33 to 8.07, and the negative likelihood ratio went from 0.13 to 0.77.

Absence of elasticity showed the best diagnostic accuracy, with a sensitivity of 87.9%, a specificity of 86.2%, and positive and negative likelihood ratios of 6.39 and 0.13, respectively.

For the separate analysis of nodules with indeterminate cytology, only the presence of microcalcifications was significantly associated with malignancy, and no ultrasound variable determined the risk of malignancy with acceptable sensitivity. Among these nodules, presence of central vascularization had the best specificity (96%).

Which Nodules Should Be Biopsied? Develop a Risk Score

According to Dr Remonti, the findings suggest that "ultrasound characteristics should not be used to select thyroid nodules for cytological diagnosis, as none of them is capable of excluding malignancy with adequate certainty.

"We believe that a meta-analysis using individual patient's data is necessary, as it would be possible to aggregate several ultrasound features in order to build a risk score for thyroid malignancy. Based on this multiple-characteristics score, clinicians would be able to select nodules that do not need further evaluation."

Dr Lee noted that the new ATA guidelines — just like the current ones — will include all of the features discussed in this paper except for "absence of elasticity," since elastography isn't yet widely practiced in the United States, and will also provide size criteria for which nodules should be biopsied.

Regarding elastography, Dr Remonti and colleagues note that it is "a new technique and may be a good tool to select patients at increased risk for thyroid malignancy. Nevertheless, more studies are required to standardize the technique and confirm its usefulness."

Dr Remonti has no relevant financial relationships. Disclosures for the coauthors are listed in the article. Dr Lee has no relevant financial relationships.

Thyroid.2015;25:538-550.Article