Hypothesis : Therapeutic intensification by increasing the dose delivered to the tumor by RCMI (conformational radiotherapy by intensity modulation) in order to reduce local relapse, often associated with poor prognosis

Primary objective: evaluate the rate of tumor sterilization and the toxicities of RTCT with concomitant boost in intensity modulation in patients with rectal cancer CT3-T4 and / or cN1-2.

Inclusion Criteria:

1. Adenocarcinoma of the rectum cT3 or cT4 or cN+, M0 and for which CPR recommends preoperative radiochemotherapy
2. Tumor <15 cm of the anal margin in rigid or subperitoneal rectoscopy at the MRI
3. Tumor potentially resectable from the outset, or considered to be resectable after radiochemotherapy
4. Operable Patient
5. Age between 18 and 75
6. OMS performance status 0-2
7. No co-morbidity likely to prevent the delivery of treatment
8. Adequate contraception for men, and for non-menopausal women
9. Neurotrophic neutrophils 1500 / mm3, platelets 100 000 / mm3, and hemoglobin 10 g / dL
10. Bilirubin ≤ 1.5 times the upper limit of normal (LNS), ASAT and ALAT ≤ 1.5LNS, Alkaline phosphatase ≤ 1.5 LNS
11. Creatinine clearance> 50 mL / min
12. Patient must have been informed and must have signed the specific informed consent form.
13. Patient must be affiliated to a Social Health Insurance.

Exclusion Criteria:

1. Remote metastasis
2. Cancer not resectable
3. Contraindication to capecitabine and its excipients
4. Previous history of pelvic radiotherapy or previous chemotherapy
5. History of inflammatory bowel or rectum disease
6. History of angina pectoris monitored or myocardial infarction or heart failure
7. Active active infection or other serious underlying condition that may prevent the patient from receiving treatment
8. Other concomitant cancer, or history of cancer other than in situ cancer of the treated cervix or basal cell carcinoma or squamous cell carcinoma
9. Patient already included in another therapeutic trial with an experimental molecule
10. Pregnant woman, likely to be pregnant or nursing
11. Persons deprived of their liberty or under guardianship
12. Patient unable to comply with the required medical follow-up for geographic, social or psychological reasons