The aim of the present phase III study is two-folded: 1) to show a superiority of external beam radiotherapy combined with a brachytherapy boost versus exclusive external beam radiotherapy and 2) to evaluate the economic impact of each treatment.

The study includes 33 cancer centres, the inclusion time is of 2 years and the follow-up is of 5 years.

Inclusion Criteria:

• age between 18 and 80 years;
• life expectancy of greater than 10 years;
• prostate adenocarcinoma histologically proven;
• prostate cancer has to be of intermediate-risk based on at least one of the three following criteria: PSA between 10 ng/ml and 20 ng/ml, and/or a Gleason score of 7 and/or a T2B. Karnofsky performance status ≥ 60% and consequently performance status ECOG 0-2.
• the patient has to be the beneficiary of the social security system (order n° 2006-477 from April 26th 2006);
• the signed consent form.

Exclusion Criteria:

• PSA level > 20;
• Gleason > 7;
• clinical T3A or T3B or MRI (a simple suspicion/ doubt on the MRI regarding the T3A won't be an exclusion criterion);
• prostate volume > 60 cc;
• pelvic lymph nodes involvement at dissection or imaging (ADP > 1.5 cm);
• concurrent hormone therapy;
• the presence of distant metastasis (M1);
• history of abdominal or pelvic irradiation;
• history of prostate resection in the previous 6 months and/or not allowing the implantation of markers;
• history of uncontrolled cancer and/or treated since less than 5 years (excepting the basal-cell carcinoma);
• urinary discomfort with an IPSS (International Prostate Symptom Score) > 15 (without alpha-blocking);
• inflammatory bowel disorder such as ulcerative colitis or the Crohn's disease;
• other undergoing study that may interfere with the present study;
• patient under legal protection measure.