FOLH1 and prostate cancer: The PET response assessment approach for bone metastases in prostate cancer using PSMA PET may be extended to other targeted PET tracers, such as 18F-NaF and 18F-FDHT in prostate cancer, 18F-FES in breast cancer and 18F-FDG and 68Ga-fibroblast activation protein inhibitors (68Ga-FAPI) in a multitude of cancer types (94, 99–102).