Inclusion Criteria:
* Histologically confirmed adenocarcinoma of the prostate per original diagnosis, with undergoing androgen deprivation therapy such as prior bilateral orchiectomy or surgical castration or LHRH-agonists/LHRH-antagonists.
* Suspected recurrence of prostate cancer based on rising PSA under androgen deprivation therapy. Recurrent castration resistant prostate cancer patients are defined by a rising PSA \>1 ng/mL under ADT or surgical castration and with testosterone castration levels \< 1.7 nM (PCWG3 criteria).
* Negative, equivocal findings or oligometastatic disease (\< 5) for prostate cancer on conventional imaging bone scan AND 2) abdomen-pelvis CT/MRI and chest CT or FDG-PET/CT or 18F-NaF PET/CT performed as standard of care workup within 90 days of signing the ICF.
* The subject is candidate for second line androgen axis targeted inhibitors such as enzalutamide and planned to receive it.
* Life expectancy ≥6 months as determined by the investigator
* Able and willing to provide signed informed consent and comply with protocol requirement
* PSA doubling time less or equal to 10 months
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 at screening.
* Able to swallow the study drug and comply with study requirements.
Exclusion Criteria:
* Subjects administered any high energy (\>300 KeV) gamma-emitting radioisotope within 5 physical half-lives prior to study drug injection.
* Receipt of investigational drug therapy for prostate cancer within 60 days of Day 1.
* Known or suspected brain metastasis or active leptomeningeal disease.
* Prior cytotoxic chemotherapy, aminoglutethimide, ketoconazole, abiraterone acetate, or enzalutamide for prostate cancer.
* History of seizure or any condition that may predispose to seizure (e.g., prior cortical stroke or significant brain trauma). History of loss of consciousness (unless of cardiac origin) or transient ischemic attack within 12 months before enrollment.
* Major surgery within 4 weeks before randomization date.
* Absolute neutrophil count \< 1000/μL, platelet count \< 100,000/μL, or hemoglobin \< 10 g/dL (6.2 mmol/L) at screening.
* Total bilirubin ≥ 1.5-times the upper limit of normal or alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥ 2.5-times the upper limit of normal at screening.
* Creatinine \> 2 mg/dL (177 μmol/L) at screening.
* Albumin \< 3.0 g/dL (30 g/L) at screening.
* Clinically significant cardiovascular disease
* Gastrointestinal disorder affecting absorption.
* Ongoing drug or alcohol abuse as per investigator judgment.
* Subject has received any investigational radioactive agent within 28 days or 5 half-lives, whichever is longer, prior to screening.
* Subjects with any medical condition or other circumstances that, in the opinion of the investigator, compromise obtaining reliable data, achieving study objectives, or completing the study.
* Contraindication to enzalutamide
* Treatment with specific (5-α reductase inhibitors, estrogens, cyproterone actetate, biologic agents with antitumor activity, systemic glucocorticoids, androgens, ...) within 4 weeks of day 1 and during the study treatment period
