PURPOSE: This study aimed to examine the association between the maximum standardized uptake value (SUVmax) of different molecular subtypes of primary breast cancer with axillary lymph node (ALN) metastasis. METHODS: The medical records of 633 patients, who underwent 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET/CT) for preoperative staging, were retrospectively reviewed. The cohort was stratified by the following molecular subtypes with immunohistochemical examination: luminal A, luminal B, human epidermal growth factor receptor 2 positive (HER2+), and triple negative. We evaluated the optimal cutoff SUVmax to predict ALN metastasis in each subtype using the receiver operating characteristic (ROC) analysis. Moreover, the risk factors for ALN metastasis were evaluated. RESULTS: Overall, the SUVmax was positively correlated with the number of metastatic ALN (p=0.001). The mean SUVmax was higher in aggressive subtypes (4.5±0.2, 6.1±0.4, 6.5±0.5, and 7.5±0.5 in luminal A, luminal B, HER2+, and triple negative, respectively, p<0.001). Upon ROC analysis, the SUVmax of the HER2+ subtype predicted ALN metastasis most accurately, with a cutoff value of 5.5, area under the curve (AUC) of 0.708, sensitivity of 74.2%, and specificity of 64.6% (p=0.002). The triple negative subtype did not show a significant difference in SUVmax between patients with and without metastasis (p=0.13). Subtype-adjusted SUVmax, HER2 positivity, lymphovascular invasion, and T stage were significant predictors for ALN metastasis. CONCLUSION The SUVmax of primary breast cancer may be an independent predictor of ALN metastasis, being the most accurate in the HER2+ subtype. As PET/CT could facilitate tailored axillary management, this approach could be considered for the initial staging and treatment planning in patients with breast cancer.

PURPOSE: The 40S ribosomal protein S6 kinase-1 (S6K1) is a crucial downstream effector of the PI3K/AKT/mTOR pathway. S6K1 overexpression is found in 10% to 30% of breast cancers and is associated with aggressive disease and poor prognosis. Herein, we investigated the relationship between the expression of phosphorylated S6K1 (p-S6K1) and efficacy of lapatinib in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. METHODS: We retrospectively analyzed the data of 36 patients with HER2-positive metastatic breast cancer treated with lapatinib between January 2010 and September 2014. The p-S6K1 expression status of the primary tumor was assessed via immunohistochemistry using a mouse monoclonal antibody. RESULTS: Fourteen of the 36 patients (38.9%) had p-S6K1-positive tumors. The median progression-free survival (PFS) of patients with p-S6K1-positive tumors was significantly longer than that of patients with p-S6K1-negative tumors (13.4 months vs. 7.1 months, p=0.025). In multivariate analysis, p-S6K1 positivity remained an independent, favorable predictive factor for PFS (hazard ratio, 0.32; 95% confidence interval, 0.11–0.97; p=0.044). CONCLUSION: The high expression of p-S6K1 was significantly associated with prolonged PFS, suggesting that p-S6K1 can be a potential biomarker for predicting the efficacy of lapatinib in patients with HER2-positive metastatic breast cancer.
Animals ; Breast Neoplasms* ; Breast* ; Disease-Free Survival ; Epidermal Growth Factor* ; Humans* ; Immunohistochemistry ; Mice ; Multivariate Analysis ; Prognosis ; Receptor, Epidermal Growth Factor* ; Retrospective Studies ; Ribosomal Protein S6 ; Ribosomal Protein S6 Kinases