Identification of Axillary Lymph Node Metastasis in Patients With Breast Cancer Using Dual-Phase FDG PET/CT

OBJECTIVE. The aim of this study was to assess the diagnostic performance of dual-phase ¹⁸F-FDG PET/CT in detecting axillary lymph node metastasis in patients with breast cancer. MATERIALS AND METHODS. A total of 826 patients with breast cancer were retrospectively evaluated. PET/CT scans were performed 1 hour and 2 hours after FDG administration before treatment. The maximum standardized uptake value (SUV_max) in the axillary lymph node at both time points (hereafter referred to as SUV_max1 and SUV_max2, respectively) and the retention index (RI) were calculated. RESULTS. Axillary lymph node metastasis was detected in 285 of 826 patients (34.5%). The median axillary SUV_max1, SUV_max2, and RI in patients with nodal metastasis were higher than those in patients without metastasis (1.5 vs 0.6, 1.6 vs 0.5, and 7.7 vs -3.7, respectively; all p < 0.001). The diagnostic accuracy of axillary SUV_max1 and SUV_max2 was equivalent, and the sensitivity and specificity of SUV_max1 were 74.7% and 83.4%, respectively. Although the performance of the axillary RI was inferior to that of SUV_max1 and SUV_max2, both the SUV_max and the RI were independent predictors of nodal metastasis, and a positive RI suggested axillary lymph node involvement when the SUV_max1 was significantly high. Of 533 patients with category T1-2 breast cancer without lymph node swelling, 101 (19.0%) had pathologic lymph node involvement; the negative predictive value of axillary SUV_max1 was 86.8%. CONCLUSION. Delayed phase imaging identified axillary lymph node metastasis as accurately as standard PET/CT. A high negative predictive value of PET/CT for the detection of nodal metastasis is helpful to avoid surgical axillary assessment in patients with category T1-2 breast cancer without lymph node swelling.