Is Vascular Flow a Predictor of Malignant Thyroid Nodules? A Meta-analysis

Background: Several reports have proposed that increased vascular flow on color Doppler sonography may be associated with malignancy in thyroid nodules. Others have described no correlation between the presence of flow and risk of malignancy. The purpose of this study was to determine whether the vascularity of a thyroid nodule can aid in the prediction of malignancy by performing a meta-analysis of the current literature.

Methods: Independent reviewers conducted a systematic review of publications from PubMed, EMBASE, and the Cochrane Database of Systematic Review using the following keyword searches: "vascular thyroid nodule", and "vascular malignant thyroid nodule". Outcomes included vascular flow pattern, nodule size, calcifications, echogenicity, margins, and shape. Data were extracted following review of appropriate studies, and outcome differences were calculated using analysis of variance and the Bonferroni method.

Results: Eighty-nine publications were identified and 14 prospective studies met inclusion criteria totaling 4,154 thyroid nodules, 1,419 (34%) of which were malignant. Thirty-three percent of malignant thyroid nodules had no vascular flow, while 17% had peripheral and 50% had internal vascular flow. There was no significant difference in vascular flow (95% CI: -14.329, 4.257), or peripheral vascular flow rate between malignant and benign thyroid nodules (95% CI: -29.254, 4.313). Also, there was no significant difference in internal vascularity between malignant and benign thyroid nodules (95% CI: -72.067, 2.824).

Conclusions: It appears that utilization of vascular flow on color Doppler sonography may not accurately predict malignancy in thyroid nodules. Further studies are warranted to investigate the predictive role of increased vascularity in diagnosing suspicious thyroid nodules.