The purpose of the study is to evaluate the predictive value of 18F-fluoromisonidazol-PET (FMISO-PET), 2-18F-fluoro-2-deoxy-d-glukose-PET-CT (FDG-PET-CT), Diffusion-Weighted Magnetic Resonance Imaging (DWI-MRI) and Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) for patients with anal cancer receiving radiation therapy +/- chemotherapy (Cisplatin and 5-FU).

The study involves tree MRI sessions, two FDG-PET-CT sessions and one FMISO-PET session. The FMISO-PET session is presently not carried out because of delivery problems. The production of 18F-fluoromisonidazol at The Department of Clinical Physiology and Nuclear Medicine, Copenhagen University Hospital Herlev, Denmark has not jet been approved by the Danish Medicines Agency.

Inclusion Criteria:

• Histological confirmation of invasive primary squamous cell carcinoma of the anal canal or perianal region.
• TNM stage T1-4, N0-3, M0-1
• Treatment with curative intent
• Age > 18 years
• Able to provide informed consent

Exclusion Criteria:

• Contraindication to MRI imaging
• Cardiac pacemaker
• Major obesity
• Serious claustrophobia
• Other malignant disease (except non-melanoma skin cancer) in a period of 5 years prior to imaging study
• Poorly regulated diabetes mellitus despite insulin
• Pregnancy
• Breast feeding
• Known allergy to iv contrast agent
• Major psychiatric illness which would prevent participation in the imaging study
• Infectious wounds on the legs
• Unacceptable kidney function
• Major language difficulties which would prevent participation in the imaging study

Patients with anal canal or perianal cancer