Pelvic R0 Resection Rate

Group 1

Patients will receive FOLFOX chemotherapy once every two weeks for 6 cycles total over a period of 12 weeks. After completing FOLFOX chemotherapy, the patient will have an MRI scan or endorectal ultrasound (ERUS) to examine the tumor. If the tumor has not decreased in size by at least 20%, the patient will receive 5FUCMT (radiation with chemotherapy). If the tumor has decreased in size by 20%, then the patient will proceed directly to surgery. \> \> If all borders of the tumor are normal post surgery, then the patient receives six additional cycles of FOLFOX chemotherapy. If all borders of the tumor are not normal then the patient receives chemoradiation therapy for 5.5 weeks after surgery. After chemoradiation, additional cycles of FOLFOX or similar chemotherapy will be recommended for 4 cycles or 8 weeks. \> \> FOLFOX (chemotherapy): Oxaliplatin 85 mg/m\^2 IV over 2 hours on day 1, leucovorin 400 mg/m\^2 bolus IV over 2 hours on day 1 and 5-fluorouracil 400 mg/m\^2 bolus over 5-15 minutes then 2400 mg/m\^2 continual over 46-48 hours total dose IV on days 1-2. The treatment schedule repeats based on the group. * FUCMT (chemoradiation): 5-fluorouracil 225 mg/m\^2 per day continuous IV infusion administered concurrently with radiation therapy for 5 or 7 days per week OR capecitabine 825 mg/m\^2 twice daily administered orally and concurrently with radiation therapy for 5 days per week.

Group 2

Patients receive 5FUCMT including chemotherapy and radiation therapy for 5.5 weeks. Patients will be given either 5-fluorouracil or capecitabine and radiation therapy. After the chemoradiation therapy is completed, patients will proceed directly to surgery. Post-surgery, patients will receive FOLFOX chemotherapy once every two weeks for 8 cycles total over a period of 16 weeks. Patient observation with follow up evaluations and event monitoring will occur up to 8 years post randomization. \> \> FOLFOX (chemotherapy): Oxaliplatin 85 mg/m\^2 IV over 2 hours on day 1, leucovorin 400 mg/m\^2 bolus IV over 2 hours on day 1 and 5-fluorouracil 400 mg/m\^2 bolus over 5-15 minutes then 2400 mg/m\^2 continual over 46-48 hours total dose IV on days 1-2. The treatment schedule repeats based on the group. Dose modifications are allowed based on adverse events. \> \> 5 FUCMT (chemoradiation): 5-fluorouracil 225 mg/m\^2 per day continuous IV infusion administered concurrently with radiation therapy for 5 or 7 days per week OR capecitabine 825 mg/m\^2 twice daily administered orally and concurrently with radiation therapy for 5 days per week. Dose modifications are allowed based on adverse events. \> \> surgery: low anterior resection with total mesorectal excision

Analysis denominator · Participants