Inclusion Criteria:

- Low-lying, low- to moderate-risk pathologically-confirmed rectal cancer (stage uT3n)
or uT1-3N+

- Negative workup for distant disease

- > 18 years of age

- Pre-treatment workup completed including:

- history and physical

- CT or MRI of the abdomen and pelvis

- endoscopic tumor evaluation (biopsy, blood work to assess CEA and hematopoietic,
renal and liver function)

- if female of child-bearing age, negative pregnancy test

- Recommendation to undergo preoperative concurrent chemoradiation, as determined by
the treating physician

- Informed consent reviewed and signed

Exclusion Criteria:

- Not deemed a candidate for preoperative chemoradiation for medical reasons, such as
uncontrolled infection (including HIV), uncontrolled diabetes mellitus or cardiac
disease

- Hemoglobin ≤ 10.0 g/dL (transfusion allowed to achieve or maintain levels)

- ANC ≤ 1,500/cubic mm³

- Platelet count ≤ 100,000/mm³

- ALT and AST ≥ 2.5 times upper level of normal (ULN)

- Alkaline phosphatase ≥ 2.5 times ULN

- Total bilirubin ≥ 1.5 times ULN

- Creatinine clearance < 50 mL/min

- Creatinine ≥ 1.5 times ULN

- Not deemed a candidate for concurrent preoperative chemoradiation for social reasons,
such as psychiatric illness

- Not deemed a surgical candidate

- Currently active second malignancy, except non-melanoma skin cancer, non-invasive
bladder cancer, low risk adenocarcinoma of the prostate and carcinoma in situ of the
cervix

- Previous pelvic radiation therapy

- History of severe reaction to gadolinium

- Inability to tolerate MRI (e.g., inability to lie flat for > 1 hour)

- Presence of a pacemaker, intracranial aneurysm clip, bladder stimulator, cochlear
implant or metal near eyes

- Body Mass Index (BMI) > 35

- Pregnant or lactating female