Adult male patients with high-risk, localized prostate cancer and planning to undergo radiation therapy (RT) with androgen deprivation therapy (ADT) will undergo an advanced Magnetic Resonance Imaging (MRI) examination called Restriction Spectrum Imaging (RSI-MRI) to evaluate whether RSI-MRI can predict treatment response.

Participants will undergo RSI at three time points: before therapy (MRI #1), after neoadjuvant ADT (MRI #2), and after radiotherapy (MRI #3). Treatment response will be assessed primarily by absence of biochemical recurrence (PSA ≥2 ng/mL greater than nadir) within 3 years of completing radiotherapy. Change in RSI cellularity index from MRI #1 to MRI #2 will be evaluated for prediction of participants who will experience biochemical recurrence within 3 years, using area under the receiver operating characteristic curve. We hypothesize that RSI cellularity index will be an early biomarker for treatment effectiveness in prostate cancer treated with ADT and radiotherapy.

Inclusion Criteria:

• Male, aged ≥18 years, with histologically confirmed adenocarcinoma of the prostate
• High-risk prostate cancer (any of: PSA ≥20 ng/mL or cT3-T4 stage or Gleason score ≥8)
• Intended treatment and follow-up according to standard of care for prostate cancer
• Planning to undergo definitive radiotherapy with neoadjuvant and concurrent androgen deprivation therapy
• In good general health as evidenced by medical history and Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• Provision of signed and dated informed consent form
• Stated willingness to comply with all study procedures and availability for the duration of the study

Exclusion Criteria:

• Prior radiotherapy to the pelvis
• Prior treatment for prostate cancer (cryotherapy, high frequency focused ultrasound, prostatectomy)
• Hip prosthesis
• Contraindication to MRI, per institutional requirements
• Technetium-99 bone scan showing no clear evidence of distant metastasis
• MRI or CT scan of the pelvis showing no clear evidence of bone or distant metastasis
• Another malignancy, unless in remission or unlikely to impact the patient's survival or ability to receive standard care for prostate cancer (e.g., cutaneous basal cell carcinoma)
• Patient has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the subject to participate, in the opinion of the treating investigator.

Male subjects undergoing treatment for Prostate Cancer