Clinical impact of 18F-FMISO PET in the distinction of intrinsic subtypes of breast cancer

570 Objectives Intrinsic molecular subtypes of breast cancer have been used in terms of treatment decision making and prognosis prediction, but the relation between these subtypes and tumor microenvironment are not fully investigated. The aim of this study is to assess the relation between the intrinsic subtypes of breast cancer and the tumor microenvironment measured by 18F-FDG PET and 18F-fluoromisonidazole (FMISO). Methods The protocol of this study was approved by the institutional ethics committee, and all patients gave written informed consent before entering the study. A total of 60 patients with newly diagnosed breast cancer (aged 32-80 y, median 55 y) were enrolled in this study, and 63 lesions were analyzed. Based on the immunohistochemical staining of the tissues obtained by operation or needle biopsy, expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2) were quantitatively measured and dichotomized into positive or negative. The results of MIB-1 staining were also dichotomized into high or low at the cut off level of 20%. Maximum standardized uptake value (SUVmax) of 18F-FDG and 18F-FMISO PET were compared with the presence of each subtype. Among the intrinsic subtypes of Luminal A (LuA), Luminal B HER2 negative (LuB-HN), Luminal B HER2 positive (LuB-HP), HER2 enriched (H2E), and triple negative (TN), variance of SUVmax of each tracer were evaluated by one-way ANOVA test. Data were expressed with mean and standard deviation, and a P value Results No significant difference of 18F-FDG uptake was observed between positive and negative in ER (8.9 ± 5.8 vs 9.3 ± 5.3, P = 0.56), PR (8.2 ± 4.9 vs 9.4 ± 5.2, P = 0.28) and HER2 (8.1 ± 3.7 vs 9.3 ± 5.7, P = 0.86) by paired t-test. Meanwhile, significant difference of 18F-FMISO uptake was observed between positive and negative in ER (2.0 ± 0.7 vs 2.8 ± 1.3, P Conclusions Tumor uptake of 18F-FMISO showed significant difference in the expression of hormone receptors as well as cell proliferation, and it indicates that intrinsic subtypes of breast cancer are related to the tumor hypoxia to some extent. 18F-FMISO can be a valuable modality to evaluate tumor microenvironment, and it has the possibility to be a powerful non-invasive tool for the treatment decision making and prognosis prediction.