Inclusion Criteria:

- Men ≥ 21 years of age with a life expectancy estimated to be > 10-years.

- Diagnosis of adenocarcinoma of the prostate confirmed by MSKCC or participating site
pathology review.

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- Prostate cancer clinical stage T1c-T2a

- PSA < 10ng/mL (this will be the PSA level prompting the prostate biopsy)

- MRI evidence of one-sided disease performed within 3 months of registration

- Prostate size <60 cc at time of treatment- if the prostate is larger, hormonal
therapy is allowed to achieve the required size Screening biopsy parameters:

- Minimum of 10 biopsy cores

- Gleason grade 7 in two cores or less, with no primary Gleason grade 4 or 5 in any
cores

- Unilateral cancer (only right-sided or left-sided, not bilateral)

- No more than 50 % cancer in any one biopsy core

- No more than 25 % of cores containing cancer

- Repeat transrectal or transperineal prostate biopsy that must meet the following
parameters:

- Minimum of 12 biopsy cores

- Unilateral cancer (only right-sided or left-sided, not bilateral)

- Gleason grade 7 in two cores or less, with no primary Gleason grade 4 or 5 in any
cores

- No more than 50 % cancer in any one biopsy core

- No more than 25 % of cores containing cancer

Subject Exclusion Criteria:

- Medically unfit for anesthesia

- Evidence or suspicion of extracapsular extension on MRI

- IPSS score > 18

- Unable to receive MRI

- Prior radiotherapy for the current disease