The WATER IV study is a multicenter, prospective, randomized clinical trial that aims to evaluate the safety and efficacy of Aquablation therapy in men with localized prostate cancer.

The WATER IV AS sub-study is a multicenter, prospective, randomized clinical trial that aims to evaluate the safety and efficacy of Aquablation therapy in men with low to intermediate risk localized prostate cancer who are candidates for active surveillance. Participants will be randomized to either Aquablation Therapy or active surveillance and followed up to 10 years.

Inclusion Criteria:

1. Biological male with age ≥ 45 years at the time of consent
2. Biopsy positive Grade Group 2 prostate cancer or biopsy positive Grade Group 1 MRI visible lesion (PI-RADS/Likert ≥ 3)
3. First prostate cancer diagnoses within 18 months (545 days) of consent
4. Are candidates for active surveillance
5. Clinical Stage ≤ T2c
6. PSA < 15 ng/ml
7. Prostate volume ≥25 ml

Exclusion Criteria:

1. Any prior or current local or systemic treatment for prostate cancer, including but not limited to surgery, radiation therapy (external or brachytherapy), tissue ablation, hormone therapy or chemotherapy.
2. Patients with previous surgical or minimally invasive treatment of benign prostatic hyperplasia within the prior 3 months of study treatment.
3. Evidence of lymph node, bone metastasis, extracapsular extension or seminal vesicle invasion.
4. Patient is unwilling to accept a blood transfusion if required.
5. Any condition or history of illness or surgery that may pose an additional risk to patients undergoing the Aquablation or radical prostatectomy procedure such as:

5a. Medical conditions that preclude the use of anesthesia; 5b. Any condition or history of active rectal inflammatory bowel disease or other factors which might increase the risk of rectal injury (i.e. fistula formation); 5c. Patient is unable to stop anticoagulants or antiplatelet agents prior to study treatment per standard of care; 5d. Any other condition or history of infection, illness or surgery that in the opinion of the investigator might affect the outcome of the study procedure, study conduct, and study results; or pose additional risks to the patient (e.g., other cancer, active urethral stricture disease).

6. Patients who are unable to provide informed consent due to cognitive impairment, legal status (such as incarceration), or other factors limiting autonomy or unwilling or unable to follow study instructions including randomization and complete all required study visits through 10 years. This includes individuals with severe cognitive disabilities, those under legal guardianship, or those currently incarcerated.

7. Patient currently participating in other studies unless approved by Sponsor in writing.

8. More than one complete biopsy beyond the diagnostic biopsy comprising both a systematic biopsy and biopsy of any MRI visible lesion (PI-RADS/Likert ≥ 3).

9. GG2 disease with PSA ≥ 10 OR stage ≥ T2b OR ≥ 50% of biopsy cores positive (multiple cores taken from any MRI visible lesion are counted as one continuous core).