Eligibility Criteria

1. Histologic confirmation of adenocarcinoma of the rectum.
2. The lesion must be located in the rectum. For purposes of this study, the lesion must be within 12 cm of the anus as measured by sigmoidoscopy.
3. Patients must have indication of a locally advanced lesion defined for this study as tumor through the bowel wall (> T3) or involving regional lymph nodes (>N1). Clinical stage determination may be made by physical examination (for T4 lesions only), endoscopic ultrasound or CT scan of pelvis.
4. Patients with metastatic disease are eligible provided operative intervention on primary site is anticipated.
5. Patients must have adequate organ function defined as pretreatment leukocyte count > 3,000/ul, platelet count > 100,000/ul, serum creatinine < 2.0 mg/dl, serum bilirubin < 2 mg/dl. Note: Capecitabine is contraindicated in patients with severe renal impairment (creatinine clearance < 30 ml/min). In patients with calculated creatinine clearance of 30-50 ml/min capecitabine will begin at (-)1 level dose reduction (see section 6.3)
6. Patients must be at least 18 years of age and have a Zubrod performance status of < 2 (see appendix 1.)
7. Patients must be informed of the investigational nature of this study and provide written informed consent in accordance with institutional and federal guidelines prior to the initiation of therapy.

Exclusion Criteria:

1. Patients may not have received previous pelvic irradiation for any indication, or previous chemotherapy for cancer therapy within the preceding 6 months.
2. Patients must have no other serious medical or psychiatric illness that would limit the ability of the patient to receive protocol therapy or provide informed consent.
3. Pregnant or lactating women may not participate. Women/men of reproductive potential must agree to use an effective contraceptive method.
4. Patients with lack of physical integrity of the upper gastrointestinal tract, inability to swallow tablets or those who have malabsorption syndrome are not eligible.