Evaluation of Rectal Cancer Treatment Response Using PET/MRI

Inclusion Criteria:

- A diagnosis of histopathologically confirmed rectal adenocarcinoma.

- Locally advanced disease as determined by ERUS or pelvic MRI. Endoscopy reports should
clearly state both the T and N stage.

- Patients with cT2N1-3M0 or cT2-4NxM0 will be considered eligible for participation.

- Age ≥18.

- Ability to understand a written informed consent document and the willingness to sign
it.

- Tumor must be determined to be surgically resectable. Surgical resection is planned to
take place at UCSF.

- Neoadjuvant chemoradiation prior to resection is planned..

- ECOG performance status of 0, 1 or 2.

Exclusion Criteria:

- ERUS tumor state of T1.

- Radiographic evidence of metastatic disease

- Weight in excess of limitations of the scanner or girth that prohibits entry into the
bore of the PET/CT scanner due to size.

- Any medical condition which impairs the ability to lie flat and without movement for
15 minutes (e.g. cough, severe arthritis, etc.)

- Prior receipt of any therapy, including local excision, radiation or chemotherapy, for
the diagnosed rectal adenocarcinoma.

- Prior history of pelvic radiation.

- Uncontrolled hyperglycemia (defined as inability to achieve a glucose of <250 mg/dL at
time of FDG injection).

- Impaired renal function (CKD 4 or 5: eGFR < 30 mLs/min), which is a contraindication
to gadolinium containing contrast.

- Known allergy to gadolinium containing contrast agents.

- Contraindication to use of fluoropyrimidines as a radiosensitizing agent.

- Pregnancy or nursing. Women of child bearing potential must have a negative serum or
urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of HCG) within
72 hours prior to randomization. This is because of the potential teratogenic effects
of the involved imaging modalities, radiation, and chemotherapy.