Of the 50,000 prostate cancers that occur each year in France, more than half will benefit from curative radiotherapy, alone or in combination with hormone therapy from 6 months to 3 years depending on the stage of the disease. At present, there are few ways to predict the response to this irradiation.

Evaluating the early response of tumor tissue to irradiation could predict the final response to treatment. It is difficult to offer biopsies during treatment for reasons of patient comfort. This is why this study consists in analysing transcriptomic and protein responses (immunohistochemistry) to irradiation on ex vivo prostate explants. These explants will be irradiated after culture and the transcriptional and immunohistochemical changes analysed before and after irradiation to determine an early tumor tissue response profile to irradiation.

Inclusion Criteria:

1. ≥ 18 years old

2. Patient with non-operated prostate adenocarcinoma for whom radiotherapy treatment is scheduled

3. Signed Informed Consent

4. No contraindications to biopsy performance:

   • No anticoagulant treatment in progress
   • Absence of infection during diagnostic biopsies
   • Absence of pain requiring level 2 analgesics during diagnostic biopsies
   • Absence of bleeding complications during diagnostic biopsies
   • Absence of anal stenosis

5. Normal coagulation examination :

   • Prothrombin Ratio between 80 and 100%.
   • Active Cephalin Time from 24 to 41 seconds, > 1.5 times that of the indicator
   • Platelets > 150,000 G/L
   • International Normalised Ratio(INR) = 1 after stopping the anticoagulant

6. No contraindication to MRI:

   • Ocular metallic foreign body
   • Pacemaker
   • Old mechanical heart valve
   • Ancient vascular clips on cranial aneurysms

Exclusion Criteria:

1. History of radical prostatectomy. A history of transurethral prostate resection is not a contraindication
2. History of prostate infection
3. Hemorrhagic complications in diagnostic biopsies
4. Pain requiring level 2 analgesics in diagnostic biopsies
5. Anticoagulant treatment in progress (aspirin will be stopped 1 week before biopsies are performed)
6. Abnormal coagulation assessment
7. Anal stenosis
8. Contraindications to radiotherapy: chronic inflammatory bowel disease, scleroderma
9. Protected or tutored patient
10. Patient whose follow-up at two years is not possible