Evaluation of Late Toxicity Following Intensity-Modulated Radiotherapy and Two Image-Guided Strategies With Corresponding Treatment Margins.

The Calypso® System (Varian Medical Systems, Inc., Palo Alto, CA) is a recent technology using electromagnetic transponders implanted within the prostate. It is a real-time target tracking system that takes into account both inter- and intrafractional target motion. So the exact position and movement of the prostate can be determined during radiation therapy treatment. The aim of this study is to assess pelvic late toxicity rate after intensity-modulated radiotherapy (IMRT) when using the Calypso® System with a reduction of treatment margins. In this randomized study, patients will receive IGRT treatment using the Calypso system or a conventional IGRT treatment.

Inclusion Criteria: * Localized prostate cancer, histologically proven. * No evidence of metastases (M0). No evidence of lymph nodes involvement (N0) (bilateral lymph node dissection is not mandatory if lymph node involvement risk is low according to the Partin tables). * Low-risk or intermediate clinical stage according to the D'Amico classification (T1-T2 and Gleason \< 8 and PSA \< 20 ng/ml) (appendix 3). * No grade \> 2 urinary or rectal clinical sign or symptom according to the CTCAE V4.03 scale. * Performance status ECOG ≤ 1. * No hip prosthesis or metallic vascular graft near the prostate. * No endopenian stent. * No pace maker, implanted defibrillator or neurostimulator. * No allergy to local anesthetics. * No irreversible anticoagulation or antiplatelet treatment for the implantation period. * Pelvic and abdominal anatomy compatible with the use of the Calypso® system (predictive detector to fiducials distance less than 19 cm, evaluated on planning CT-scan) (distance from skin surface to prostate center less than 17 cm). * Patient aged ≥ 18 and less than 80 years old. * Dated and signed written informed consent available. * Patients must be affiliated to a French Social Security System. Exclusion Criteria: * Indication of pelvic nodes irradiation. * Prior pelvic irradiation. * Biopsy-proven seminal vesicle invasion. * Prior bilateral orchiectomy. * Prior radical prostatectomy. * Other malignancy except adequately-treated basal cell carcinoma of the skin or other malignancy from which the patient has been disease-free for at least 5 years. * Psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial. * Other uncontrolled systemic disease (cardiovascular, renal, liver, pulmonary embolism, etc.). * Known VIH positive patients (no specific test needed). * Known homozygote ATM Mutation (Ataxia telengiectasia).