The purpose of this study is to test the ability of a new PET scan radiotracer, called FDHT (stands for [18F] Dihydro-Testosterone), to better find and monitor prostate cancer. Radiotracers are a type of drug that carries small amounts of radioactivity that can be seen by the PET scanner. FDHT is a radiotracer that looks for a protein which is present in almost all prostate cancer cells. The investigators want to find out if we can find and monitor changes in cancer using a FDHT PET scan.

Inclusion Criteria:

• Male aged 21 years or older and below 80 years of age.

• Signed written informed consent and willingness to comply with protocol requirements.

• Histologically confirmed diagnosis of prostate cancer.

• Staging imaging workup including a baseline MRI of the prostate and pelvis performed at MSKCC.

• Baseline imaging to rule out distant metastatic disease (99mTc bone scan, NaF PET, total body MRI, or CT chest/abdomen/pelvis)

• Karnofsky performance status ≥ 70

• Clinical criteria required to be eligible:

  a. One of the following i.Pre-treatment PSA ≥10 ng/dL, OR ii. Clinical T-stage assessed by digital rectal exam of ≥T2a, OR ii . Radiographic ≥T3a on MRI, OR iv. Gleason score of ≥3+4=7 c. Visible intraprostatic tumor foci ≥1 cm in largest dimension on T2-weighted images based on initial pre-treatment MRI

• Physician recommendation of ADT.

Exclusion Criteria:

• Metastatic disease on standard staging imaging (beyond regional lymph node involvement).

  o Absence of metastatic disease (beyond regional lymph node involvement) as defined by a negative bone scan, NaF PET, CT chest/abdomen/pelvis, or total body MRI.

• Prior treatment of the prostate gland for malignant conditions (surgery, cryotherapy, radiotherapy, or photodynamic therapy).

• Physician prescription of androgen receptor antagonist therapy (examples: bicalutamide, flutamide, or enzalutamide) during time of protocol scans.

  o Note: ADT consists of chemical castration (i.e. degarelix) to remove endogenous DHT. Androgen receptor antagonists will bind to the androgen receptor and inhibit FDHT from binding.

• Patients receiving testosterone supplementation .

• Any contraindication to baseline MRI based on departmental MR questionnaire, or inability to cooperate for an MRI scan.

• History of allergic reactions attributed to compounds of similar chemical or biologic composition to FDHT.

• Hepatic laboratory values:

  1. Bilirubin >1.5 x ULN (institutional upper limits of normal)
  2. AST/ALT >2.5 x ULN
  3. Albumin <2 g/dL

• Creatinine >2.5 mg/dL

• Calcium >11 mg/dL

• Other serious illness(es) which might preclude completion of this study or interfere with determination of causality of any adverse effects experienced in this study.