18 F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Predicts the Function of Tumor Immune Microenvironment in Early Triple-Negative Breast Cancer

Abstract BackgroundThe maximum standardized uptake value (SUVmax) on 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is presumed to visualize not only tumor cells but also active immune cells in the tumor microenvironment based on their glycolysis activity. This study aimed to investigate the relationship between SUVmax on FDG PET/CT and tumor-infiltrating lymphocyte (TIL) subsets.MethodsFifty-four patients with invasive triple-negative breast cancer (TNBC) underwent FDG PET/CT before neoadjuvant chemotherapy, and pre-treatment biopsy specimens were pathologically evaluated. The expression status 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 relationship between TIL subsets and SUVmax or pathological complete response (pCR) was investigated.ResultsTILs, CD8, FOXP3, PD-1, and PD-L1 were high in 15 (27.8%), 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 (P = 0.003, P = 0.043, and P = 0.017, respectively). In multiple linear regression analysis, tumor size and CD8/FOXP3 ratio predicted SUVmax (P < 0.001 and P = 0.045, respectively). Seventeen patients (31.5%) achieved a pCR. TILs, CD8/FOXP3 ratio, PD-1, and PD-L1 were significantly correlated with the pCR rate. In multivariate analysis, the CD8/FOXP3 ratio was the only independent predictive factor for pCR (P = 0.010).ConclusionSUVmax on FDG PET/CT was related to tumor biological factors and the immune microenvironment after adjusting for confounding factors in TNBC. FDG uptake was influenced by the CD8/FOXP3 ratio, which predicts pCR after neoadjuvant chemotherapy.