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

Abstract

Background: To assess the predictive value of ¹⁸F-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.

Keywords: Breast cancer; False positivity; Lymph node metastasis; Mediastinal lymph node; Positron emission tomography.

Fig. 1

(A) ROC curve analysis in lymph node metastasis according to the SUV of mediastinal lymph nodes and (B) Graph demonstrating positive (PPV) and negative predictive values (NPV) of FDG-PET/CT for detecting mediastinal lymph node metastasis.

Fig. 2

The distribution of histopathological findings, based on a mediastinal lymph node SUV_max cut-off value of 6.4.

Fig. 3

Overall survival curves of patients with (A) a mediastinal lymph node SUV_max of greater than 6.4 and 6.4 or less, and (B) those with or without mediastinal lymph node metastasis detected histopathologically.

Fig. 4

(A) The FDG-PET/CT images of a representative patients delivered during initial staging. The FDG-PET/CT revealed increased FDG uptake in the upper quadrant of the right breast (SUV_max = 12.3) (thin arrow) and increased uptake in the subcarinal lymph node (thick arrow) with SUV_max 10.4 and 31 × 14 mm in size, which was biopsied and confirmed a diagnosis of tuberculosis. (B) The FDG-PET/CT images of a representative patients delivered at the time of disease progression revealed increased FDG uptake at subcarinal (SUV_max = 10.6) and prevascular lymph nodes (SUV_max = 9.8); the histopathological finding was malignant.