Phase II Non-Randomized Study Evaluating POSLUMA-PSMA PET Response After Oligo- Metastatic/Progressive-directed Treatment With Radiotherapy (PROMPT-R)

Inclusion Criteria: * Documented informed consent of the participant or legally authorized representative. * Age: ≥ 18 years * KPS ≥ 70 or ECOG 0-1 (Appendix A) * Biopsy-confirmed diagnosis of castration-sensitive prostate adenocarcinoma, as defined by rising PSA in setting of T\>100 * Clinical diagnosis of de novo oligometastatic or oligoprogressive disease, as defined by one the following: De novo oligometastatic: newly diagnosed prostate cancer AND ≤ five metastatic sites outside of the pelvis (Metastatic sites may not be brain or liver.) OR Hormone Sensitive Oligoprogressive: history of prior local therapy for prostate cancer AND ≤ five progressing metastatic sites outside of the pelvis (Metastatic sites may not be brain or liver.) AND Hormone sensitive defined as clinical progression in absence of castration (T\>100) * Measurable disease by PERCIST v1.0 * Eligible to receive ablative-intent radiation therapy (biologically effective dose \[BED\] \>100, α/β ratio:2) directed to all sites of metastatic disease. * Primary site of disease (Prostate +/- Seminal Vesicles) is controlled or will receive ablative intent treatment as a part of this treatment course. * Baseline flotufolastat F18 PET imaging, if obtained as part of standard of care, is acceptable provided it was performed prior to the initiation of radiation therapy. * Agreement by females and males of childbearing potential\* to use an effective method of birth control or abstain from heterosexual activity for th…