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Serial [18F]-FDHT-PET to predict bicalutamide efficacy in patients with androgen receptor positive metastatic breast cancer.

Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands; Department of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Department of Internal Medicine, Medical Center Leeuwarden, Leeuwarden, the Netherlands. Medical Imaging Center, Department of Radiology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Electronic address: c.p.schroder@umcg.nl.

European journal of cancer (Oxford, England : 1990). 2021;:151-161
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Abstract

BACKGROUND The androgen receptor (AR) is a potential target in metastatic breast cancer (MBC), and 16β-[18F]-fluoro-5α-dihydrotestosterone positron emission tomography ([18F]-FDHT-PET) can be used for noninvasive visualisation of AR. [18F]-FDHT uptake reduction during AR-targeting therapy reflects AR occupancy and might be predictive for treatment response. We assessed the feasibility of [18F]-FDHT-PET to detect changes in AR availability during bicalutamide treatment and correlated these changes with treatment response. PATIENTS AND METHODS Patients with AR + MBC, regardless of oestrogen receptor status, received an [18F]-FDHT-PET at baseline and after 4-6 weeks bicalutamide treatment. Baseline [18F]-FDHT uptake was expressed as maximum standardised uptake value. Percentage change in tracer uptake, corrected for background activity (SUVcor), between baseline and follow-up PET scan (% reduction), was assessed per-patient and lesion. Clinical benefit was determined in accordance with Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 or clinical evaluation (absence of disease progression for ≥24 weeks). RESULTS Baseline [18F]-FDHT-PET in 21 patients detected 341 of 515 lesions found with standard imaging and 21 new lesions. Follow-up [18F]-FDHT-PET was evaluable in 17 patients with 349 lesions, showing a decrease in median SUVcor from 1.3 to 0.7 per-patient and lesion (P < 0.001). Median % reduction per-patient was -45% and per-lesion -39%. In patients with progressive disease (n = 11), median % reduction was -30% versus -53% for patients who showed clinical benefit (in accordance with RECIST (n = 3) or clinical evaluation (n = 3); P = 0.338). CONCLUSION In this feasibility study, a bicalutamide-induced reduction in [18F]-FDHT uptake could be detected by follow-up [18F]-FDHT-PET in patients with AR + MBC. However, this change could not predict bicalutamide response. CLINICAL TRIAL INFORMATION NCT02697032.

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Publication Type : Clinical Trial

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