Gene Expression and FDG PET/MRI in Evaluating Treatment Response in Patients With Locally Advanced Rectal Cancer Undergoing Chemotherapy and Radiation Therapy Before Surgery

Inclusion Criteria:

• Biopsy-proven adenocarcinoma of the rectum.
• Surgical candidate.
• Candidate for neoadjuvant chemotherapy.
• Clinical evidence of T1-3N1 or T3N0 disease. This can be either by imaging studies or by physical exam findings.
• At least 18 years of age.
• Zubrod performance status of 0-2.
• Able to understand and willing to sign a written informed consent document.
• Patients with distant metastatic disease will be eligible if they satisfy all other conditions.

Exclusion Criteria:

• Pregnant.
• Past history of pelvic radiotherapy.
• Received prior chemotherapy for colorectal cancer.
• Uncontrolled diabetes with a fasting glucose ≥ 200 mg/dl at the time of PET/MRI imaging.
• Claustrophobia or any other contraindication to MRI imaging evaluated by a standardized safety questionnaire.
• Renal insufficiency (defined as glomerular filtration rate (GFR < 30 mL/min/1.73 m2) measured no more than 60 days before the first research scan) which precludes safe administration of the contrast agent.
• Currently on dialysis.
• Known prior allergic reaction to gadolinium-based MR contrast agents.