The primary objective of this study is to evaluate the impact of Patient's Therapeutic Education (PTE) in Adapted Physical Activity (APA) ans dietetic on the reduction of interventions number on rectal volume (laxative or probe).

The secondary objectives are to evaluate the contribution of Patient's Therapeutic Education (PTE) between the 2 arms on repositionnind during the radiotherapy session, the gastrointestinal toxicity, the need to use laxative or transit regulating treatment or techniques, the quality of life, the undernutrition and food intake, the evolution in eating/hydratation and physical habits.

For the experimetal arm, the satisfaction and the compliance with PTE program will be evaluated, as well as the need of additionnal use of dietary and APA consultations.

Prostate cancer is the 3rd cause of cancer mortality in patient aged over 50 years. Radiotherapy treatment plans require specific conditions:

• Reproductibility of patient's positioning (requiring management of bladder and rectal fillings at each session).
• An image-guided treatment consisting in acquiring an image before each session. This pre-treatment Imaging allows the optimal adjustment of the target volume and organs at risk (bladder and rectum).

To allow reproductibility of target volume positioning at each radiotherapy session, it's recommended to have an empty rectum at the time of the radiotherapy preparation scan, and to check repletion before each session.

It's recommended that the patient has a comfortably full bladder to limit the volume of irradiated bladder mucosa. The radiotherapy teams don't have any recommendations concerning the rectum and manage this problem session by session, according to the repositioning Imaging of the current day.

According to a pilot study carried out in 2017 in the radiotherapy department of the Léon Bérard center, an intervention for a dilated rectum (probe or laxative) was necessary for an average of 25% of session per patient.

These rectal problems can be partly explained by the age (60-80 years) and sedentary lifestyle of patients with prostate cancer. Physical activities, adapted hydratation and changes in eating habits are an integral part of the constipation and flatulence prevention.

Inclusion Criteria:

I1: Age >= 18 years old.

I2: Patient with prostatic adenocarcinoma with indication for first-line or post-operative radiotherapy (adjuvant or biologic recurrence).

I3: Patient able to practice a physical activity (certificate of aptitude for adapted physical activity).

I4: Life expectancy greater than 6 months.

I5: Absence of chronic inflammatory intestinal disease or intestinal surgery.

I6: Signed informed consent.

I7: Patient covered by a medical insurance.

I8. At least 20 sessions of radiotherapy planned

Exclusion Criteria:

E1: Patient does not understand and cannot read French.

E2: Patient followed for a psychiatric pathology or presenting cognitive disorders.

E3: Inability to comply with study follow-up goegraphical, social or psychological reasons.

E4: Patient requiring tutorship or curatorship or patient deprived of liberty.

E5: Participation to another clinical trial which may interfere with principal Endpoint assessment.