[¹⁸F]-FDHT PET/CT as a tool for imaging androgen receptor expression in high-grade glioma

G lioblastoma (GBM) is associated with poor overall survival. Recently, we showed that androgen receptor (AR) protein is overexpressed in 56% of GBM specimens and AR antagonists induced dose-dependent death in several GBM cell lines and significantly reduced tumor growth and prolonged the lifespan of mice implanted with human GBM. 16β-18F-fluoro-5α-dihydrotestosterone ([¹⁸F]-FDHT) is a positron emission tomography (PET) tracer used to detect AR expression in prostate and breast cancers. This study was aimed at exploring the ability of [¹⁸F]-FDHT-PET to detect AR expression in high-grade gliomas.

Twelve patients with suspected high-grade glioma underwent a regular workup and additional dynamic and static [¹⁸F]-FDHT-PET/CT. Visual and quantitative analyses of [¹⁸ F]-FDHT kinetics in the tumor and normal brain were performed. Mean and maximum (max) standardized uptake values (SUVs) were determined in selected volumes of interest. The patients had surgery or biopsy after PET/CT. AR protein was analyzed in the tumor samples by western blot. Fold change in AR expression was calculated by densitometry analysis. Correlation between imaging and AR protein samples was determined.

In six of the 12 patients, [¹⁸ F]-FDHT uptake was significantly higher in the tumor than in the normal brain. These patients also had increased AR protein expression within the tumor. Pearson correlation coefficient analysis for the tumor-to-control normal brain uptake ratio in terms of SUV_mean versus AR protein expression was positive and significant (R = 0.84; P = .002).

[¹⁸ F]-FDHT-PET/CT could identify increased AR expression in high-grade glioma.