Inclusion Criteria:

- Male, 45 years of age or older

- Diagnosis of prostate adenocarcinoma

- Clinical stage T1c or T2a

- Gleason score of 7 or less

- A minimum of 12 biopsy cores sampled during diagnostic biopsy

- Three or fewer biopsy cores with prostate cancer

- No single biopsy core with greater than 50% of tumor involvement

- A radiographically visible prostate lesion on MRI with concordance to biopsy sextant

- A documented Karnofsky performance status of at least 70

- Estimated survival of 20 years or greater, as determined by treating physician

- Ability to give informed consent

Exclusion Criteria:

- Previous surgery, radiation, or androgen deprivation therapy for prostate cancer

- Presence of any condition (e.g., metal implant, shrapnel) not compatible with MRI

- History of previous pelvic radiation

- Severe lower urinary tract symptoms as measured by an International Prostate Symptom
Score (IPSS) of 20 or greater. (See Appendix A)

- History of other primary non-skin malignancy within previous three years