The use of 18F-FDG positron emission tomography to detect mediastinal lymph nodes in metastatic breast cancer

BACKGROUND: To assess the predictive value of (18)F-fluorodeoxyglucose positron-emission tomography (FDG–PET/CT) in detecting mediastinal lymph node metastasis with histopathologic verification in breast cancer (BC) patients. MATERIALS AND METHODS: Between February 2012 and October 2019, 37 BC patients who underwent histopathological verification for FDG-PET positive mediastinal lymph nodes were retrospectively analyzed. Nine patients (24%) were screened before beginning treatment, while 27 (76%) were screened at the time of disease progression, an average of 39 months after completion of initial treatment. RESULTS: The histopathologic diagnosis revealed lymph node metastasis from BC in 15 patients (40%) and benign disease in 22 patients (60%). The standardized uptake value (SUV(max)) of mediastinal lymph nodes was significantly higher in patients with lymph node metastasis compared to those with benign histology (9.0 ± 3.5 vs. 5.9 ± 2.4; P = 0.007). The cut-off value of SUV(max) after the ROC curve analysis for pathological lymph node metastasis was 6.4. Two of the 15 patients with mediastinal SUV(max) ≤ 6.4 and 13 of the 22 patients with SUV(max) > 6.4 had lymph node metastasis. Age and pathological findings were prognostic factors for overall survival in univariate analysis. The treatment decision was changed in 19 patients (51%) after mediastinoscopic evaluation of the entire cohort. CONCLUSIONS: This is the first study to support the need for pathologic confirmation of a positive PET/CT result following evaluation of mediastinal lymph nodes for staging BC, either at initial diagnosis or at the time of progression. Treatment decisions were consequently altered for nearly half of the patients.