Phase 3, Multicenter, Randomized Study, Evaluating the Efficacy and Tolerability of Focused HIFU (High Intensity Focused Ultrasound) Therapy Compared to Active Surveillance in Patients With Significant Low Risk Prostate Cancer

Inclusion Criteria:

• Patient having been clearly informed of the study and having accepted, withsufficient reflection time, to participate by signing the informed consent form ofthe study.

• Age between 50 and 80 years with a life expectancy of more than 5 years. Patientsbetween the ages of 75 and 80 will need to have G8 score > 14.

• Initial diagnosis of localized prostate cancer (T1c or T2a) with the followingcharacteristics:

• Only one Target tumor on MRI on a maximum of 2 contigous sextants. Caseallowed:

• If more than one target tumor on MRI, only one of them must be confirmedby targeted prostate biopsies.

• If no target tumor on MRI, only 2 contigous sextants must be positive onprostate biopsies

• A maximum tumor length> 3 mm or at least 3 positive biopsies on all biopsiesperformed (randomized biopsies and/or MRI/Ultrasound Fusion-Guided ProstateBiopsy).

• Gleason 6 score (risk group 1 of the D'Amico classification).

• Tumor positioned so that a safety distance of at least 9 mm from externalsphincter can be defined during HIFU-FOCAL treatment in prostate tissue aroundthe target.

• PSA ≤ 15ng / ml.

• Patient affiliated with health insurance or beneficiary of an equivalent plan.

Exclusion Criteria:

• Contraindications to treatment with HIFU-F:

• Tumor not accessible.

• Multiple intra prostatic calcifications inducing, on ultrasound, a shadow conein the prostate preventing the penetration of ultrasound and thus therealization of the treatment.

• History of pelvic irradiation

• Presence of an implant (stent, catheter) located less than 1 cm from thetreatment area.

• Fistula of the urinary tract or rectum.

• Anal or rectal fibrosis, anal or rectal stenosis or other abnormalities makingit difficult to insert the Focal One® probe.

• Anatomical abnormality of the rectum or rectal mucosa.

• Patient with artificial sphincter, penile prosthesis or intra prostaticimplant, eg stent.

• History of intestinal inflammatory pathology.

• Uro-genital infection in progress (the infection to be treated before HIFUtreatment).

• Anterior surgery at the level of the anus or rectum making the introduction ofthe probe impossible.

• Allergy to latex.

• Thickness of the rectal wall> 10mm.

• TURP indication. Bladder neck incision is allowed .

• Patient with a medical contraindication to Sonovue® injection.

• Patient with a medical contraindication on MRI.

• Patient already treated for prostate cancer (hormone therapy, radiotherapy,surgery).

• History of uncontrolled cancer and / or treated for less than 5 years (with theexception of basal cell skin cancer).

• History of sclerosis of the bladder neck or urethral stenosis.

• Patient with a several bleeding risk according to medical advice (patient with oralanticoagulant therapy must receive an alternative therapy if randomized in HIFU-Farm).

• Patients with unstable neurological pathology.

• Patient who has been treated for a therapeutic trial within 30 days of enrollment orwho wishes to participate in an ongoing study that may interfere with this study.

• Legal person protected by law.

• Patient not able to understand the objectives of the study or refusing to complywith postoperative instructions.