Inclusion Criteria:

- no prior therapy for rectal cancer

- pathological/ cytological diagnosis of adenocarcinoma of the rectum. Patients must
have operable rectal cancer that is amenable to surgery.

- adequate organ function

- Eastern Cooperative Oncology Group (ECOG) Performance status 0 or 1

- signed informed consent

- at least 18 years of age

- surgically sterile, postmenopausal (women) or compliant with a medically approved
contraceptive regimen during and for 6 months after the treatment.

Exclusion Criteria:

- concurrent administration of any other anti-tumor therapy

- treatment within the last 30 days with a drug that has not received regulatory
approval for any indication at the time of study entry

- serious concomitant systemic disorders

- previously completed or withdrawn from this study

- pregnant or breast-feeding

- second primary malignancy

- history of significant neurological or mental disorder, including seizures or
dementia

- inability to interrupt aspirin or other nonsteroidal anto-inflammatory drugs (NSAIDs)

- presence of clinically relevant third space fluid collections that cannot be
controlled by drainage or other procedure prior to the study entry

- inability or unwillingness to take folic acid, vitamin B12 or dexamethasone