Vargas HA, et al. - Researchers prospectively assessed the reproducibility and repeatability of ¹⁸F-fluorodihydrotestosterone (18F-FDHT) (a radiolabeled analog of the androgen receptor’s primary ligand) in men with metastatic castration-resistant prostate cancer as part of the biomarker qualification process. High repeatability and interobserver reproducibility were demonstrated by the uptake metrics derived from ¹⁸F-FDHT PET/CT. Repeatability was not significantly affected by the five most avid lesions per patient, only lesions 4.2 mL or more, only lesions with an SUV of 4 g/mL or more, or normalizing of SUV to area under the parent plasma activity concentration–time curve, including the most avid lesion per patient.