title: 18F-fluoromisonidazole PET/CT: a potential tool for predicting primary endocrine therapy resistance in breast cancer.
abstract: Although endocrine therapy is an effective method to treat estrogen receptor (ER)-positive breast cancer, approximately 30%-40% of all hormone receptor-positive tumors display de novo resistance. The aim of our current study was to analyze whether (18)F-labeled fluoromisonidazole (1-(2-nitro-1-imidazolyl)-2-hydroxy-3-fluoropropane [(18)F-FMISO]) PET/CT could predict primary resistance to hormonal therapy in ER-positive breast cancer.
  
  
  METHODS
  Postmenopausal women who had ER-α-positive breast cancer, stages II-IV, and had never received prior endocrine therapy were prospectively enrolled in this study. Patients underwent both (18)F-FDG and (18)F-FMISO PET/CT scans before and after treatment. The hottest (18)F-FDG standardized uptake value (SUV) in the tumor foci, the SUVs at 2 and 4 h, and the TBR2 h and TBR4 h for the target lesions were calculated (TBR2 h = SUV2 hT/SUV2 hB and TBR4 h = SUV4 hT/SUV4 hB [TBR is the tumor-to-background ratio]). Clinical outcomes of primary endocrine therapy with letrozole were evaluated according to the criteria of the World Health Organization after at least 3 mo of treatment. Immunohistochemistry for markers of proliferation (Ki67) and hypoxia-induced factor 1α was performed on a subset of tumors that had undergone biopsy or surgery. Pearson and Spearman analysis was used to determine the correlation between the parameters of (18)F-FDG and (18)F-FMISO uptake and clinical or immunohistochemistry outcomes with a 0.01 threshold for statistical significance.
  
  
  RESULTS
  A total of 45 lesions (13 primary, 32 metastatic) from 20 patients met the inclusion criteria in this study. Baseline (18)F-FDG and (18)F-FMISO PET/CT scans were obtained for 33 lesions from 16 patients. The correlation between baseline (18)F-FDG uptake and clinical outcome was weak and did not reach statistical significance (r = 0.37, P = 0.031). However, there was a significantly positive correlation between baseline (18)F-FMISO uptake (SUV2 hT, TBR2 h, SUV4 hT, and TBR4 h) and clinical outcomes after ≥3 mo of primary endocrine therapy with letrozole (r = 0.77, 0.76, 0.71, and 0.78, respectively; P < 0.0001). The application of a TBR4 h cutoff of ≥1.2 allowed the prediction of 88% of the cases of progressive disease (15/17). Despite poor correlation between (18)F-FMISO uptake and hypoxia-induced factor 1α expression, a marginal positive correlation between TBR4 h and Ki67 expression was measured (r = 0.51, P = 0.011) in a subset of malignant lesions acquired by biopsy or surgery.
  
  
  CONCLUSIONS
  (18)F-FMISO PET/CT can be used to predict primary endocrine resistance in ER-positive breast cancer.
authors: Department of Nuclear Medicine, Fudan University Shanghai Cancer Center, Shanghai, China.
authors: Jingyi
authors: J
authors: Cheng
authors: Li
authors: L
authors: Lei
authors: Junyan
authors: J
authors: Xu
authors: Yifei
authors: Y
authors: Sun
authors: Yongping
authors: Y
authors: Zhang
authors: Xincun
authors: X
authors: Wang
authors: Lingling
authors: L
authors: Pan
authors: Zhimin
authors: Z
authors: Shao
authors: Yingjian
authors: Y
authors: Zhang
authors: Guangyu
authors: G
authors: Liu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D047072:Aromatase Inhibitors / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D000077289:Letrozole; D008875:Middle Aged; D008920:Misonidazole / Q000031:analogs & derivatives*; D064847:Multimodal Imaging; D009376:Neoplasms, Hormone-Dependent / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000378:metabolism; D009570:Nitriles / Q000627:therapeutic use; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed; D014230:Triazoles / Q000627:therapeutic use
chemical_list: D047072:Aromatase Inhibitors; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D005462:Fluorine Radioisotopes; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019394:Ki-67 Antigen; D009570:Nitriles; D019275:Radiopharmaceuticals; D014230:Triazoles; C031843:fluoromisonidazole; D019788:Fluorodeoxyglucose F18; D000077289:Letrozole; D008920:Misonidazole