There is no established standard preoperative treatment in rectal cancer. Two large randomized studies in North America closed from lack of accrual; therefore the only method of assessing preoperative treatment in rectal cancer is from Phase II studies. This study builds on the experience at PMH gained in two previous studies which demonstrated a lower than expected toxicity with concurrent 5FU infusion and external radiotherapy. The current standard at PMH is preoperative radiation, 46Gy in 23 fractions with concurrent 5FU infusion 225mg/m2. An increase of radiation dose and consequent increase in chemotherapy may improve the response rate, but may also increase toxicity. It is proposed to increase the dose of radiotherapy to 50Gy in 25 fractions with concurrent chemotherapy and measure acute toxicity and complete remission rate.

Inclusion Criteria:

• Biopsy proven adenocarcinoma of the rectum
• Performance status <2 (ECOG, appendix II)
• Clinical Stage T2 N1-2, T3-4 NO-2, without evidence of distant metastasis

Exclusion Criteria:

• Prior pelvic irradiation
• Inflammatory bowel disease
• Evidence of distant metastasis
• Performance status >2