Two Fraction Prostate SBRT With DIL SIB

Inclusion Criteria:

* Patient age greater than or equal 18
* Localized adenocarcinoma of the prostate
* Biopsy-proven diagnosis of prostate adenocarcinoma
* Low to intermediate risk National Comprehensive Cancer Network (NCCN) disease

  * TX-T2c-8th addition staging
  * PSA\<20 ng/ml
  * Grade group 3 or less
* Proper rectal space replacement required as determined by the treating radiation oncologist
* Prostate size less than 60cc defined at time of simulation based on MRI
* Patient ability to undergo MRI and documented dominant Prostate Imaging Reporting and Data System (PI-RADS) 3 or higher lesion

  \-- Exception is very low risk, low risk, or favorable intermediate risk with a low to intermediate decipher score in which case an SIB is not utilized
* Androgen-deprivation therapy (ADT) is left to the discretion of the treating radiation oncologist
* Agreement to use effective contraceptive methods such as condoms and spermicidal foam, intrauterine device, or for their partner to use prescription birth control pills
* Ability to give informed consent

Exclusion Criteria:

* High risk disease
* Pelvic lymph node involvement
* Prophylactic lymph node irradiation requirement as determined by the treating radiation oncologist
* Evidence of clinical or radiological extracapsular extension or seminal vesicle invasion
* Prior radiation to the pelvis
* Prior malignancies within the last 5 years
* Inability to meet pre-specified 2 fraction DVH constraints
* Prostate size \> 60cc as measures at treatment planning MRI
* Active significant inflammatory bowel disease (IBD) or rheumatological disease
* Prior prostate surgeries

  * Previous uro lift
  * Transurethral resection of the prostate (TURP) within 6 months of SBRT
* "Reasonable" urinary, bowel, and erectile function as defined by the pre-treatment EPIC questionnaire (\>50 overall summary score for each domain)
* Men of reproductive potential may not participate unless they agree to use an effective contraceptive method