The purpose of this study is to determine whether whole-body MRI (WB-MRI) accuracy is superior to FDG-PET-CT considered as the gold-standard for the staging of distant lesions of rectal cancer.

Rectal cancer is the second cause of mortality after lung cancer in industrialized countries and represent 28% of colorectal carcinomas. Despite major improvements in diagnosis and treatment made those last years,mortality and morbidity remains high, because of high prevalence of metastasis and local recurrence. A accurate initial staging is of paramount importance for an appropriate treatment (neoadjuvant chemiotherapy and radiotherapy, surgery).

Actually, there is no international consensus concerning imaging for the staging of rectal cancer and modalities used are variable from one center to another.

WB-MRI represented a attractive and promising technique for the staging of rectal cancer, free of ionizing radiation .

Inclusion Criteria:

• rectal cancer T3 N+ or T3 or T4

Exclusion Criteria:

• renal failure
• allergy to iodinated contrast medium
• contraindication to MRI

patients with a rectal cancer