ABSTRACT
PURPOSE: Accurate preoperative detection by radiologic assessment is necessary to specifically identify patients with at least three positive nodes, who can directly undergo axillary lymph node (ALN) dissection, and avoid unnecessary surgical procedures. We evaluated the usefulness of the standardized uptake value (SUV) ratio of ALN in primary breast tumor, using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography (CT) and magnetic resonance imaging (MRI) to predict the necessity of ALN dissection during breast cancer surgery. METHODS: In this retrospective study we enrolled 316 consecutive patients with invasive breast cancer. The SUV ratio of ALN to primary breast tumor uptake was calculated. Optimal cutoff values were determined by receiver operating characteristic curve analysis for predicting the presence of ≥3 ALN metastases. Diagnostic performance of FDG-PET and MRI features for the prediction of ≥3 ALN metastases were determined by sensitivity, specificity, and diagnostic odds ratio (DOR). A subgroup analysis for FDG-avid tumors was also performed. RESULTS: Of the 316 patients, 36 (11.4%) showed involvement of ≥3 ALNs, with 101 (32%) having at least one metastatic lymph node. Axillary 18F-FDG uptake was positive in 75 patients (23.7%), and the optimal ratio of maximum SUV of axillary lymph node and primary tumor for determining ALN dissection was 0.3. MRI scans revealed suspicious ALN involvement in 147 patients (46.6%). The sensitivity and specificity of MRI detection were 88.9% and 56.2%, respectively, while for SUVLN/T ratio, they were 69.4% and 86.8%, respectively. DOR values for MRI and SUVLN/T ratio were 10.37 and 9.7, respectively. The area under the curve (AUC) was improved to 0.896 (95% confidence interval [CI], 0.817–0.975) for the SUVLN/T ratio in patients with FDG-avid primary tumors (FDG ≥3.9, n=108), but the MRI AUC was worsened (0.681; 95% CI, 0.569–0.793). The DOR, sensitivity, and specificity for the SUVLN/T ratio of FDG-avid cancers were 25.68, 89.0% and 86.0%, respectively. CONCLUSION: SUVLN/T ratio outperformed MRI features in predicting the need for ALN dissection in FDG-avid primary breast cancer. PET/CT may be a potential noninvasive diagnostic technique for identifying the presence of ≥3 ALN metastases.