Combined Evaluation of FDG-PET/CT and CT Imaging Characteristics of Cervical Lymph Nodes to Increase the Interpretation Accuracy for Nodal Metastatic Involvement in Head and Neck Cancer

Abstract

Rationale and objectives: Accurate staging of regional lymph nodes in patient with head and neck squamous cell carcinoma (HNSCC) has important therapeutic and prognostic implications. The objective of this study was to assess qualitative and quantitative imaging characteristics of cervical lymph nodes on FDG PET/CT and contrast enhanced CT (CECT), either alone or in cross-modality combinations, for more accurate diagnosis of nodal metastatic involvement in HNSCC patients who had hypermetabolic cervical lymph nodes on PET/CT imaging. Materials and methods:Lymph nodes were evaluated using quantitative PET/CT parameters (SUVmax, SUVmean, metabolic tumor volume, total lesion glycolysis) and qualitative and quantitative CT parameters (shape, margin, focal hypoattenuation, fatty hilum, short axis, long axis, volume, eccentricity factor). A subset analysis was performed on FDG-avid lymph nodes that lacked imaging findings suggestive of extracapsular spread or necrosis. Statistical outcomes included sensitivity, specificity, accuracy, positive likelihood ratio, and odds ratio. Results:In the full cohort (174 nodes), the most malignancy specific parameters were ill-defined margin and focal hypoattenuation, and the most accurate variables included SUVmax, SUVmean, ill-defined margin, short axis, and focal hypoattenuation. On multivariate analysis, ill-defined margin, short axis measurement, and SUVmax independently predicted nodal metastasis.In the subgroup of smaller lymph nodes without ill-defined margin or focal hypoattenuation (100 nodes), round shape was among the most accurate and specific criteria for malignancy. Cross-modality combination criteria with SUVmax and shape, eccentricity factor, or long to short axis ratio resulted in statistically significant improvements in specificity and accuracy for lymph node metastasis. Conclusion:A combined evaluation strategy using individual PET/CT and CECT characteristics in cross modality combinations, particularly SUVmax with round shape on axial imaging or with loss of eccentricity, can improve diagnostic accuracy of malignant nodal involvement in the evaluation of indeterminate cervical lymph nodes for malignancy.