- Arm II: Patients receive chemoradiotherapy 4-12 weeks after surgery (if circumferential resection margins are histologically involved by tumor). Radiotherapy is administered in 25 fractions over 5 weeks (5 days per week). During radiotherapy, patients either receive fluorouracil (5-FU) continuous infusion, 5-FU bolus IV and leucovorin calcium IV weekly, or a 5-day bolus schedule of 5-FU and leucovorin calcium.