Prostate Specific Membrane Antigen (PSMA) Imaging for Detection of Residual and Metastatic Prostate Cancer

• Bicalutamide (Drug), also known as Casodex: Bicalutamide is a non-steroidal androgen receptor inhibitor administered as a once a day pill taken orally. This is given as standard of care.
• Prostate-specific membrane antigen Positron Emission Tomography-Computed Tomography (Device), also known as PSMA PET-CT: Patients will undergo prostate-specific membrane antigen Positron Emission Tomography-Computed Tomography (PSMA PET-CT) imaging. Each PSMA PET-CT session will consist of 5 minutes of dynamic imaging conducted via the Biograph Vision Quadra PET-CT, a whole-body PET-CT scanner.
• 18F-rhPSMA-7.3 (Drug), also known as Polsuma, Flotufolastat F-18: Radioactive diagnostic agent for intravenous use.
• PROSTest (Diagnostic test): PROSTest is a novel, blood-based qPCR assay that assesses gene expression to diagnose PCa and predict patient outcomes to different treatments.

Primary outcomes

• Group B only: Lesion detection rates between PET1 and PET2. [Baseline and 14 days after start of bicalutamide treatment (total estimated time 14 days)]: Differences in lesion detection rates between Group B PET1 and PET2 will be analyzed by McNemar's test. Lesion detection rates will be reported by Group B patients at PET1 and PET2 scans and by the two scan sets (first 5 minutes and at 60 minutes post 18F-rhPSMA-7.3 injection).

Secondary outcomes

• Group A and B: Number of lesions detected on early scan versus delayed scan [At baseline and 14 days after start of bicalutamid treatment (total estimated time is 14 days)]: The total number of lesions detected per patient will be summarized as counts. The number of lesions will be summarized by descriptive statistics for all patients at PET1, Group A patients at PET1, Group B patients at PET1, and Group B patients at PET2 and for each, by the two scan sets (early scan = first 5 minutes and at delayed scan = 60 minutes post 18F-rhPSMA-7.3 injection).
• Group A and B: Correlation between PSA response and PROSTest after radiation therapy [Through day 90]: The correlation between PSA response and PROSTest after radiation therapy will be analyzed in Group A versus Group B. The results will be reported as a two-sample t-test or Wilcoxon sum rank test.
• Group A and B: Comparison of PSA response in patients who are treated with radiation vs. those treated with radiation [Through day 90]: The comparison of PSA response will be analyzed in patients who are treated with radiation based on results of the PET2 versus those treated with radiation based on the results of PET1. The comparison will be reported as the results of a two-sample t-test or Wilcoxon sum rank test.
• Group B only: Correlation between PSA kinetics and detection rates between PET1 and PET2 [Through day 90]: The correlation between PSA kinetics and detection rates will be reported as the results of a two sample t-test or Wilcoxon sum rank test for each timepoint, PET1 and PET2.
• Group B only: Correlation between PROSTest results and detection rates of PET1 and PET2 [14 days after start of bicalutamide treatment (total estimated time 14 days)]: Correlation between PROSTest results and detection rates of PET1 and PET2 will be reported as two sample t-test or Wilcoxon sum rank test. Results will be reported for PET1 and PET2.

Sex: Male, ages: 18 Years to any

Inclusion Criteria:

* Histologically or cytologically confirmed biochemically recurrent prostate cancer, with original diagnosis no more than 2 years from date of consent.
* Intermediate unfavorable or high-risk prostate cancer.
* All patients under consideration for radiation therapy, either at the time of first recurrence or in salvage radiation therapy will be included.
* Patients who have started bicalutamide up to a maximum of 3 days prior to randomization will be allowed to be on protocol. Otherwise, a washout period of at least 42 days will be required.
* Biological males, at least 18 years of age.
* Prostate specific antigen (PSA) < 1.0 ng/mL.
* Agreement to adhere to Lifestyle Considerations throughout study duration
* Ability to understand and willingness to sign an IRB approved written informed consent document.

Exclusion Criteria:

* Patients currently on androgen deprivation therapy (ADTs).
* Currently receiving any other investigational agents.
* A history of allergic reactions attributed to compounds of similar chemical or biologic composition to POSLUMA, furosemide, bicalutamide, or other agents used in the study.

• Vikas Prasad, MD, PhD, Principal investigator, Washington University School of Medicine