Semiquantitative Analysis of Maximum Standardized Uptake Values of Regional Lymph Nodes in Inflammatory Breast Cancer. Is There a Reliable Threshold for Differentiating Benign from Malignant?

Rationale and Objectives: The aim of this study was to determine an optimum standardized uptake value (SUV) threshold for identifying regional nodal metastasis on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomographic (PET)/computed tomographic (CT) studies of patients with inflammatory breast cancer. Materials and Methods: A database search was performed of patients newly diagnosed with inflammatory breast cancer who underwent ¹⁸F-FDG PET/CT imaging at the time of diagnosis at a single institution between January 1, 2001, and September 30, 2009. Three radiologists blinded to the histopathology of the regional lymph nodes retrospectively analyzed all ¹⁸F-FDG PET/CT images by measuring the maximum SUV (SUVmax) in visually abnormal nodes. The accuracy of ¹⁸F-FDG PET/CT image interpretation was correlated with histopathology when available. Receiver-operating characteristic curve analysis was performed to assess the diagnostic performance of PET/CT imaging. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated using three different SUV cutoff values (2.0, 2.5, and 3.0). Results: A total of 888 regional nodal basins, including bilateral axillary, infraclavicular, internal mammary, and supraclavicular lymph nodes, were evaluated in 111 patients (mean age, 56 years). Of the 888 nodal basins, 625 (70%) were negative and 263 (30%) were positive for metastasis. Malignant lymph nodes had significantly higher SUVmax than benign lymph nodes (P < .0001). An SUVmax of 2.0 showed the highest overall sensitivity (89%) and specificity (99%) for the diagnosis of malignant disease. Conclusions: SUVmax of regional lymph nodes on ¹⁸F-FDG PET/CT imaging may help differentiate benign and malignant lymph nodes in patients with inflammatory breast cancer. An SUV cutoff of 2 provided the best accuracy in identifying regional nodal metastasis in this patient population.