Pilot Study for Detection of PSMA-Low CRPC-NE Tumors With Fluciclovine PET/CT

Inclusion Criteria: * Participants must have histologically confirmed prostate cancer that is metastatic and one of the following: CRPC with PSMA-low disease defined by whole-body SUVmean ≤ 10 determined by standard-of-care 68Ga-PSMA-11 PET/CT imaging with at least 5 metastatic lesions OR NEPC pathology based on tumor biopsy. This may include morphology consistent with small cell carcinoma or mixed adenocarcinoma/NE features and/or IHC staining for NE markers. Participants should have at least 5 metastatic lesions. * Must have either already had standard of care 68Ga-PSMA PET/CT scan or be planned for 68Ga-PSMA PET/CT scan before or after the planned 18F-fluciclovine-PET/CT. * Age ≥18 years. Since no dosing or adverse event data are currently available on the use of 18F-fluciclovine in participants \<18 years of age, and most prostate cancer occurs in the adult population, children are excluded from this study but will be eligible for future pediatric trials. * ECOG performance status ≤2 (Karnofsky ≥60%, see Appendix A) * Ability and willingness to comply with the study procedures. * The effects of 18F-fluciclovine on the developing human fetus are unknown. For this reason and because radiopharmaceuticals may be teratogenic, men must agree to use adequate contraception (barrier method of birth control; abstinence) prior to study entry and for 24 hours after the PET/CT scan is completed. * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * Participants with other known malignancy requiring treatment * History of allergic reactions attributed to compounds of similar chemical or biologic composition to 18F-fluciclovine. * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Contraindications for PET/CT including: * Severe claustrophobia * Any past or current condition that in the opinion of the study investigators would confound the results of the study or pose additional risk to the patient by their participation in the study.