Prediction of Extracapsular Invasion at Metastatic Sentinel Nodes and Non-sentinel Lymph Nodal Metastases by FDG-PET in Cases with Breast Cancer.

We have previously reported that the presence of an extracapsular invasion (ECI) at sentinel lymph nodes (SLNs) is a strong predictor of non-SLN metastasis in breast cancer. We hypothesized that(18)F-fluorodeoxyglucose (FDG) uptake by metastatic SLNs reflects invasive disease, or ECI. In this study, we evaluated the association of FDG uptake with ECI on SLNs and the possibility of FDG-positron-emission tomography (PET) assessment of axillary non-SLN metastases. We retrospectively investigated the cases of 156 consecutive patients with primary breast cancer who underwent SLN biopsy and FDG-PET preoperatively. Among 35 patients (22.4%) in whom the presence of SLN metastases was diagnosed, 10 cases (28.6%) had FDG uptake in the axillary lesion. The sensitivity, specificity, overall accuracy, and false-negative rates in the diagnosis of SLN status by FDG-PET were 28.6%, 99.2%, 83.3%, and 71.4%, respectively. The false-positive rate of FDG-PET evaluation was 0.8%. The 35 cases with lymph node metastases were divided into two groups based on the presence of FDG uptake in the axillary lesions. None of the clinicopathological features of the primary tumor were significantly associated with FDG uptake in the axillary lesion. The present analysis revealed that only tumor size of the metastatic lymph node was significantly associated with FDG uptake in the axillary lesion. The two groups were not significantly different in terms of presence of ECI and non-SLN metastasis. Among the 35 cases with SLN metastases, 13 cases (37.1%) had non-SLN metastasis. Only ECI was a predictor of non-SLN involvement. FDG uptake in the axilla was not associated with non-SLN metastasis in this study. In conclusion, FDG-PET evaluation of lymph nodes is not a sufficient indicator of ECI at SLN metastasis or non-SLN metastasis, suggesting that axillary lymph node dissection cannot be avoided. However, since the positive predictive value for SLN metastasis is high, positive FDG uptake in the axillary lesions may be useful for avoiding SLN biopsy. Copyright