Evaluation of Tumor Control Based on Serial Multiparametric MRI and Post-Treatment Biopsies For Patients Treated With Dose Intensification to the Dominant Intra-Prostatic Lesion (DIL) Using Ultra-Hypofractionated, MR-Guided Radiotherapy

Eligibility Criteria

Inclusion Criteria:

1. Intermediate-risk prostate cancer patients will be eligible for this study. Risk groups will be assigned as per National Comprehensive Cancer Network (NCCN) guidelines. Intermediate-risk patients will be defined as:

* PSA 10-20 ng/ml or
* Gleason score = 7 or
* Clinical stage T2b/T2c (T2b: the tumor has spread to more than one-half of one side of the prostate, but not to both sides. T2c: the cancer has invaded both sides of the prostate)
2. Age > 18
3. Karnofsky Performance Status (KPS) > 80
4. Prostate size < 90 cc
5. Presence of a T2-visible prostatic lesion with maximum dimension of ≥ 0.5 cm and no more than two additional disease foci with a documented Prostate Imaging Reporting and Data System (PIRADS) 4-5 lesion
6. MRI findings: Lesion may contact the capsular edge, possible extracapsular extension (ECE) permitted
7. International Prostate Symptom Score < 18
8. Satisfy all MRI screening criteria and be willing to fill out the standard MRI screening form

Exclusion Criteria:

1. Gleason score >7
2. PSA >20 ng/mL
3. Prior or concurrent androgen deprivation therapy for prostate cancer
4. MRI findings: suspicious for/probable ECE
5. MRI findings: >2 disease foci identifiable
6. Evidence of metastatic disease on bone scan or MRI/CT
7. MRI ineligibility due to: the presence of a cardiac pacemaker, defibrillator, or other implanted metallic or electronic device which is considered MR unsafe; severe claustrophobia; inability to lie flat for the duration of the study; etc.
8. Metallic implant or device in the pelvis that might distort the local magnetic field and compromise quality of mp-MRI
9. Lateral pelvic separation greater than 50 cm and/or anterior-posterior separation greater than 35 cm which are incompatible with MR for Calculating ATtenuation (MRCAT) reconstruction
10. Contra-indications to receiving gadolinium contrast
11. KPS < 80
12. Pelvic or Prostate MRI or CT (MRI preferred) evidence of radiographic T3, T4, or N1 disease
13. Prior history of transurethral resection of the prostate
14. Prior history of urethral stricture
15. Prior history of pelvic irradiation
16. History of inflammatory bowel disease
17. Unable to give informed consent
18. Unable to complete quality of life questionnaires
19. Abnormal complete blood count, including any of the following:

* Platelet count less than 75,000/ml
* Hb level less than 10 gm/dl
* White blood cell (WBC) less than 3.5/ml
* Abnormal renal function tests (creatinine > 1.5)