Inclusion Criteria:

- Histologically confirmed Stage I or II rectal cancer

- Patients must be candidates for preoperative or adjuvant chemoradiation.

- Patients enrolling in the adjuvant chemoradiation cohort must have undergone surgical
resection of the primary rectal tumor between 28 and 56 days (i.e., 4-8 weeks) prior
to study treatment.

- ECOG performance status 0-1

- Adequate bone marrow, liver, and kidney function

- At least 18 years of age

- Able to give written informed consent

Exclusion Criteria:

- Treatment with prior chemotherapy or radiation for rectal cancer

- History of myocardial infarction

- Uncontrolled hypertension, unstable angina, congestive heart failure, serious cardiac
arrhythmia requiring medication or peripheral vascular disease

- History of stroke within 6 months

- History of abdominal fistula, gastrointestinal perforation, or intrabdominal abscess
within 6 months

- Symptomatic sensory or peripheral neuropathy

- Prior treatment with anti-angiogenic agents

- Prior malignancy in the past 5 years

- Active infections or serious underlying medical condition

- Major surgery less than 28 days prior

- Women who are pregnant or lactating

- Thrombolytic therapy within 10 days of starting bevacizumab

- PEG tube, G-tube, or external biliary stents

- Proteinuria

- Non healing wound, ulcer or fracture

- History of bleeding diathesis or coagulopathy

- Hemoptysis

- Participation in another experimental trial within 28 days

- Uncontrolled anticoagulant therapy