With functional imaging development, it becomes possible to increase radiation dose to radioresistant areas (located inside tumor volume) using radiotherapy dose-painting. This strategy is particularly suitable for prostate cancer where tumor hypoxia plays a major role in the resistance of these tumors to radiation.

In order to develop intratumoral hypoxia targeting by radiotherapy dose-painting areas, we should characterize changes in hypoxia before treatment and during radiotherapy.

• If hypoxia does not change during radiotherapy, radiotherapy dose-painting strategy by an "integrated" boost is performed.
• If hypoxia varied (increasing or incomplete regression), a "final" boost strategy of radiotherapy dose-painting(IMRT, stereotactic brachytherapy or high dose rate) after a first fractionated IMRT could be considered.

This study should show that PET imaging with fluoromisonidazole (18F-MISO) is an available tool to physicians in assessing tumor hypoxia.

Inclusion Criteria:

• histologically proven prostate adenocarcinoma
• Absence of metastases (lymph node or bone)
• One or more tumor nodules seen on MRI and PET Choline.
• Intermediate Risk : Gleason 7 and PSA (prostate specific antigen)<20 ng / ml, T <T2c or Gleason 6 and PSA 10-20 ng / ml, T <T2c
• No concomitant hormonal treatment. (NB: the introduction of hormone therapy during radiotherapy before the second 18F-MISO is a criterion to study exit)
• Indication of radiotherapy up to a total dose> 70 Gy and 2 Gy/day fractions
• Signed Informed consent
• Social Insurance

Exclusion Criteria:

• Age < 18 years old
• Patient protected by law