Patient eligibility has limited accrual and patient sample has changed with the change in referral patients.

The purpose of this study is to establish a prospective database of anal canal and perianal cancer patients treated with IMRT and chemotherapy with curative intent at PMH for the purposes of investigating MRI-derived primary tumor parameters. Patients who decide to participate in this study will be treated according to standard treatment policies and radiation therapy planning protocols at Princess Margaret Hospital (PMH) with radiation therapy +/- chemotherapy. IMRT for all treatment phases of radiotherapy has been implemented as standard treatment. Surgery is reserved for salvage treatment.

Anal cancer is an uncommon cancer, accounting for 2% of gastrointestinal cancers. Prognostic factors include tumor differentiation and staging, along with patient gender, race, and socioeconomic status. The standard of care is radical chemoradiation with 5-fluorouracil and mitomycin C, with surgery reserved for salvage. Intensity modulated radiation therapy (IMRT) is a specialized radiotherapy technique that may be used for anal cancer. IMRT allows the radiation dose to conform to the three-dimensional shape of the target volume more than conventional two-dimensional techniques, and it may reduce treatment toxicities without compromising tumor control. At the Princess Margaret Hospital (PMH) since July 2007, IMRT for all treatment phases of radiotherapy has been implemented as standard treatment for patients with anal canal and perianal cancer.

Inclusion Criteria:

• histological confirmation of invasive primary squamous cell carcinoma or adenocarcinoma of the anal canal or perianal region
• treatment with curative intent
• patients who are not eligible for chemotherapy and receive IMRT alone are eligible for evaluation
• primary anal or perianal cancer evaluable on cross-sectional imaging (CT or MRI) scan
• ECOG performance status of 0, 1, or 2
• age > 18 years
• able to provide informed consent

Exclusion Criteria:

• evidence of distant metastasis (M1)
• prior radiation therapy to the pelvis or contraindication to radiotherapy
• contraindication to MRI imaging
• known allergy to intravenous Gadolinium
• renal insufficiency (serum creatinine greater than 150)
• serious claustrophobia
• cardiac pacemaker
• hip prosthesis
• major medical or psychiatric illness which, in the investigator's opinion, would prevent completion of imaging study

Patients with anal canal or perianal cancer