The maximum standardized uptake value (SUVmax) obtained using ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is presumed to indicate tumor and active immune cells in the tumor immune microenvironment (TIME) based on their glycolysis activity. Therefore, this study investigated whether the metabolic parameter SUVmax could provide information regarding TIME in triple-negative breast cancer (TNBC) patients.

Fifty-four patients with TNBC underwent FDG PET/CT before neoadjuvant chemotherapy. Pretreatment biopsy specimens were pathologically evaluated. Expression statuses of CD8, forkhead box P3 (FOXP3), programmed cell death-1 (PD-1), and programmed cell death-ligand 1 (PD-L1) were assessed by immunohistochemistry. The relationships between immunological factors, including the tumor-infiltrating lymphocyte (TIL) grade and SUVmax or pathological complete response (pCR), were investigated.

CD8, FOXP3, PD-1, and PD-L1 were high in 15 (27.8%), 39 (72.2%), 18 (33.3%), and 26 (48.2%) patients, respectively. SUVmax was significantly correlated with tumor size, Ki-67 labeling index, and CD8/FOXP3 ratio. Multiple linear regression analysis indicated that tumor size and the CD8/FOXP3 ratio predicted SUVmax. Seventeen patients (31.5%) achieved a pCR; TILs, the CD8/FOXP3 ratio, PD-1, and PD-L1 were significantly correlated with pCR rate. Multivariate analysis indicated that the CD8/FOXP3 ratio was the only independent predictive factor for pCR.

SUVmax could provide metabolic information regarding TIME for TNBC patients and might be beneficial for formulating a treatment strategy and predicting pCR after neoadjuvant chemotherapy.