Value of CT added to ultrasonography for the diagnosis of lymph node metastasis in patients with thyroid cancer

Background: The benefit of CT for the diagnosis of lymph node metastasis in patients with thyroid cancer is still unclear. Methods: Three hundred fifty-one patients with thyroid cancers from 7 hospitals were prospectively enrolled in order to compare diagnostic performance between a combination of ultrasound and CT (ultrasound/CT) and ultrasound alone for prediction of lymph node metastasis and to calculate patient-based benefits of CT added to ultrasound. Results: Of 801 pathologically proven neck levels, ultrasound/CT showed higher sensitivities in both central and lateral compartments and improved accuracy in the lateral compartment compared to ultrasound alone. In the retropharyngeal/superior mediastinal compartment, although CT could detect lymph node metastasis an ultrasound could not. Patient-based benefit was demonstrated in 13.1% of patients (46/351), and was higher in patients with cancers >1 cm than cancers ≤1 cm. Conclusion: In patients with thyroid cancer, CT improved surgical planning by enhancing the sensitivity for lymph node metastasis and by detecting lymph node metastasis that was overlooked with ultrasound alone.