Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed locally advanced adenocarcinoma of the rectum (with or
without nodal involvement) requiring surgery

- Stage mrT3-4, and/or mrN1-2, M0 disease

- Tumor with K-ras gene mutation as assessed locally

- No distant metastases

PATIENT CHARACTERISTICS:

- WHO performance status 0-1

- Neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- Hemoglobin ≥ 10.0 g/dL

- Creatinine clearance ≥ 50mL/min

- AST ≤ 2.5 times upper limit of normal (ULN)

- Total bilirubin ≤ 1.5 times ULN

- PT/INR or PTT ≤ 1.5 times ULN

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective barrier contraception during and for 12 months
after completion of study therapy

- Is compliant and geographic proximity allows for proper staging and follow-up

- No other malignancy within the past 5 years except adequately treated cervical
carcinoma in situ or localized nonmelanoma skin cancer

- No psychiatric disorder that would preclude understanding study-related information,
giving informed consent, or complying with oral drug intake

- No clinically significant (i.e., active) cardiac disease (e.g., congestive heart
failure, symptomatic coronary artery disease, or cardiac arrhythmia [even if
controlled with medication]) or myocardial infarction within the past 12 months

- No uncontrolled hypertension

- No evidence or history of bleeding diathesis

- No lack of physical integrity of the upper gastrointestinal tract or malabsorption
syndrome

- No serious or underlying condition (e.g., active autoimmune disease, uncontrolled
diabetes, or uncontrolled infection) that, in the judgement of the investigator,
could preclude the ability of the patient to participate in the study

- No known hypersensitivity to study drugs or to any other component of the study drugs

PRIOR CONCURRENT THERAPY:

- No prior treatment for rectal cancer

- No prior organ allografts

- More than 4 weeks since prior major surgery other than colostomy

- More than 30 days since prior treatment in a clinical trial

- No other concurrent experimental drugs or anticancer therapy

- No concurrent brivudine, lamivudine, ribavirin, or any other nucleoside analogue

- No concurrent drugs contraindicated for use with the study drugs

- No other concurrent radiotherapy

- No concurrent anticoagulation therapy other than low molecular weight heparin