18F-DCFPyL

Background: Identifying medium- and high-risk prostate cancer early may allow for treatments to work. But identification can be hard. Researchers want to see if a radiotracer used during PET scans can help. Objective: To test how an imaging agent called 18F-DCFPyL detects response to standard prostate cancer treatment. Eligibility: People ages 18 and older with newly diagnosed prostate cancer who have no evidence of distant metastatic disease and plan to get stereotactic body radiation therapy (SBRT) with or without androgen deprivation therapy (ADT). Design: Participants will be screened with: Medical history Physical exam Blood tests MRI Participants will have baseline MRI and PET/CT scans. For the MRI, they may get a contrast agent by IV injection. For the PET/CT scan, they will get an IV injection of 18FDCFPyL. About 1 to 2 hours later, they will get the PET/CT scan. During the scans, participants will lie on their back and remain still for 45 minutes to 1 hour. These scans will be repeated at different points during the study. Participants will get SBRT with or without ADT. Participants will complete questionnaires about their quality of life. Participants will be asked about any symptoms they are having. They will also be asked about medications they are using. They may have a physical exam. Participants will give blood and urine samples. They will give a tumor sample from a biopsy they have had in the past. After treatment, participants will have follow-up visits. These will occur 1 month after treatment, then every 3 months for a year, and then every 6 months for 1 more year.

Background: The current standard treatment of prostate cancer is either surgery or radiation. Typically, this includes either the removal or radiation of the whole prostate gland. Many people now seek out focal therapy options to decrease the side effects of treatment. Until now, several forms of physical destruction with heat (thermal ablation), cold (cryotherapy), sound waves (HIFU), laser (FLA), and electrical energy (IRE). A new type of radiation (SBRT) may be an effective way to cure men of early-stage prostate cancer with fewer side effects than standard treatments. Objective: To see how people with untreated localized prostate cancer will respond to focal therapy with SBRT. Eligibility: People aged 18 years and older with untreated localized prostate cancer (prostate cancer which has not spread outside of the prostate gland). Design: * Participants will undergo screening including blood tests, an MRI, a PSMA PET/CT (18F-DCFPyL), and a biopsy. * Small, non-radioactive, gold seeds about the size of a grain of rice will be placed in and/or around the tumor to help target the radiation treatment. * Radiation (SBRT) will occur in 2 separate sessions about 1 week apart. No sedation is used, these sessions are painless. Each session will take about 1-2 hours. Participants can go home afterwards. * Follow-up will continue for 2 years with repeat scans (MRI and PSMA PET/CT) and blood (PSA) tests. * After two years, a biopsy will be done to understand the impact of this new treatment on prostate cancer.

The purpose of this research is to determine the expression of prostate specific membrane antigen (PSMA) in human epidermal growth factor receptor 2 (HER2)-negative, androgen receptor (AR)-positive metastatic breast cancer, and to determine its role in resistance to the anti-androgen, bicalutamide. The investigators hypothesize that PSMA expression will correlate with resistance to anti-androgen therapies, as has been documented in prostate cancer, and this can be used to select patients most likely to benefit from these therapies in future clinical trials. 15 people with HER2-negative, AR-positive metastatic breast cancer will be enrolled and be on study for about 3 days.