• Patients with prostate cancer must have 1-3 asymptomatic metastatic lesions that are ≤ 5.0 cm or \< 250 cm3 documented at CT/MRI or WBD-MRI.

• PSMA-PET/CT positive scan matching with lesions documented on baseline CT/MRI or WBD-MRI.

• Patients must have had their primary tumor treated with surgery and/or radiation and previous salvage radiation to the prostate bed or pelvis is allowed.

• Patients will be admitted to the therapeutic phase only if diagnostic PET/CT PSMA SUV max is ≥ 3.

• Histologic confirmation of malignancy (primary or metastatic tumor).

• Prostate specific antigen (PSA) ≥ 0.2 ng/mL but ≤ 50 ng/mL and Testosterone ≥ 125 ng/dL.

• PSA doubling time (PSADT) \< 15 months. PSADT will be calculated using as many PSA values that are available from time of relapse (PSA \> 0.2 ng/dL).

• Patients unfit or refusing ADT.

• Patients may have had prior systemic therapy and/or ADT associated with treatment of their primary prostate cancer. Patients may have had ADT associated with salvage radiation therapy.

⁃ Patients must be ≥ 18 years of age.

⁃ Patient understands the purpose of the study and the procedures required for it; the patient is willing to participate in the study and to sign a written informed consent document.

⁃ Patients must have an Eastern Cooperative Oncology Group performance status ≤ 2.

⁃ Patients should have a life expectancy of at least 6 months.

⁃ Patients must have normal organ and marrow function as defined as:

∙ Leukocytes \>2,000/μL;

‣ Absolute neutrophil count \>1,000/μL;

‣ Platelets \>75,000/μL;

‣ total bilirubin within normal institutional limits (this will not apply to patients with confirmed Gilbert's syndrome);

‣ AST(SGOT)/ALT(SGPT) ≤ 2.5 X institutional upper limit of normal;

‣ Creatinine within normal institutional limits.

⁃ If the participant engages in sexual activity with a woman of childbearing potential, a condom must be used together with another highly effective method of contraception during the Treatment Period and for 6 months after the last dose of study intervention. The participant must agree not to donate sperm for the purpose of reproduction during the Treatment Phase and for a minimum of 6 months after receiving the last dose of study intervention.

⁃ Highly effective birth control methods are required beginning at the screening visit and continuing until 6 months following last treatment with study drug. Patients and female partner who is of childbearing potential must use 2 acceptable methods of birth control (1 of which must include a condom as a barrier method of contraception, see Appendix F) starting at screening and continuing throughout the study period and for 6 months after final study drug administration. Two acceptable methods of birth control thus include Condom (barrier method of contraception) and one of the following is required ( established use of oral, or injected or implanted hormonal method of contraception by the female partner; placement of an intrauterine device (IUD) or intrauterine system (IUS) by the female partner; additional barrier method like occlusive cap with spermicidal foam/gel/film/cream/suppository in the female partner; tubal ligation in the female partner; vasectomy or other procedure resulting in infertility (eg., bilateral orchiectomy), for more than 6 months.

• 16\. Highly effective birth control methods are required beginning at the screening visit and continuing until 6 months following last treatment with study drug. Patients and female partner who is of childbearing potential must use 2 acceptable methods of birth control (1 of which must include a condom as a barrier method of contraception, starting at screening and continuing throughout the study period and for 6 months after final study drug administration.