The purpose of this research study is to collect information on a new treatment of prostate tissue participants with intermediate risk prostate cancer using a medical device called the Poseidon System. The Poseidon System is intended to ablate prostate tissue in areas of the prostate where cancer has been identified. The medical device delivers thermal energy in the form of water vapor to the prostate tissue through the urethra. Previous research has shown successful prostate tissue ablation. Additional research may help show successful ablation of the prostate tissue where cancer is located.

Inclusion Criteria:

• 45-80 years old
• Biopsy confirmed unilateral, adenocarcinoma of the prostate
• Minimum of 12 biopsy cores obtained ≥4 weeks and ≤12 months before treatment. Targeted fusion biopsy is preferred if there is a MRI PI-RADs ≥3 lesion. It is preferred a standard 12 sector biopsy is mapped. MRI required if biopsy was completed >6 months prior to treatment date to confirm no MRI progression of disease that would be considered exclusionary.
• ≤4 of 6 standard sector biopsy cores positive for prostate cancer (unilateral); positive core(s) from a targeted lesion count as one positive core.
• Gleason score of 7 (3+4) / International Society of Urological Pathologists (ISUP) Gleason Grade Group (GGG) 2
• Clinical Stage less than or equal to T2b N0 M0
• PSA (Prostate Specific Antigen) less than or equal to 15ng/mL
• Prostate size 20-80cc

Exclusion Criteria:

• Malignant tumors identified by extraprostatic extension, sphincter involvement/lesion abutment seminal vesicle invasion or lymph node invasion or metastasis
• Narrow Peripheral Zone
• MRI identified PI-RADs ≥4 lesion contralateral to the side that has biopsy confirmed adenocarcinoma
• Prior definitive treatment of prostate cancer