Predictive value of estimated tumor volume measured by ultrasonography for occult central lymph node metastasis in papillary thyroid carcinoma

The clinical and prognostic value of tumor volume in various solid tumors has been investigated. However, there have been few studies on the clinical impact of tumor volume in papillary thyroid carcinoma (PTC). This study was performed to investigate the predictive value of estimated tumor volume measured by ultrasonography for occult central neck metastasis (OCNM) of PTC. A total of 264 patients with clinically node-negative PTC on ultrasonography and computed tomography who underwent total thyroidectomy in conjunction with at least ipsilateral prophylactic central neck dissection were enrolled in this study. Tumor volume was derived with the formula used to calculate ellipsoids from two orthogonal scans during 2-D ultrasonography at initial aspiration biopsy. We retrospectively evaluated demographic characteristics, pre-operative ultrasonographic features (tumor size, volume and multifocality) and pathologic results. The OCNM rate was 35.6%; estimated tumor volume was used to predict OCNM (p = 0.035). At 0.385 mL, sensitivity and specificity were 51.1% and 66.5%, and the area under the curve for OCNM detection was 0.610. In multivariate analysis, tumor volume, but not size, was an independent predictive factor for OCNM (odds ratio = 1.83, p = 0.029). The other factors were extrathyroidal extension (odds ratio = 2.39, p = 0.004) and male gender (odds ratio = 3.90, p < 0.001). The estimated tumor volume of PTC measured by ultrasonography could be a pre-operative predictor of OCNM.