64Cu-ATSM PET/CT in Rectum Cancer (TEP 64Cu-ATSM-Rectum)

Inclusion Criteria: * Histologically confirmed rectum adenocarcinoma * Locally advanced, non metastatic disease, with or without locoregional lymph node involvement (greater than or equal to T3 +/- N), first-line therapy * 18 Years and older * Performance Status equal to 0 or 1 * Fertile patients must use effective contraception * Hemoglobin greater than 9g/dl, neutrophils greater than 1 500/mm3, platelets greater than 100 000/mm3 * Creatinine clearance greater than or equal to 50ml/min * Plan to receive treatment with concurrent chemotherapy and radiation therapy followed by surgery * Totality of the tumor included in the radiotherapy field * Written informed consent * Patient must be affiliated to a Social Health Insurance Exclusion Criteria: * metastatic disease * Patient contraindicated for capecitabine or 5FU (5-Fluoro-Uracile) derivatives (history of severe and unexpected reactions to fluoropyrimidine-containing therapy, known hypersensitivity to 5FU, to any of the excipients, or known total DPD (dihydropyrimidine déshydrogénase) deficiency) * Known Contraindication to perform MRI * Previous treatment with pelvic radiotherapy * Chronic inflammatory bowel disease, malabsorption, lack of colonic integrity * Diarrhea grade greater than 2 * Contraindication to surgery * Bilateral total hip prosthesis * Other malignancy treated within the last 5 years (except non-melanoma skin cancer or in situ carcinoma of the cervix) * Pregnant or nursing patient * Individual deprived of liberty or placed under the authority of a tutor * Impossibility to submit to the medical follow-up of this clinical trial for geographical, social or psychological reasons * Agitation; impossibility of lying motionless for at least 1 hour, or known claustrophobia