The addition of Oxaliplatin to conventionally fractionated chemoradiation (FULV or capecitabine) is considered as standard in unresectable rectal cancer by the panel of experts. The Investigators addressed the question whether short-course preoperative radiotherapy with consolidating chemotherapy of FOLFOX4 may increase the rate of R0 resection in patients with unresectable rectal cancer.

Patients with unresectable primary rectal cancer or with unresectable local recurrence without distant metastases are randomly allocated to control or experimental arm. The preoperative treatment in the control arm is conventionally fractionated chemoradiation with 50.4 Gy total dose in 28 fractions of 1.8 Gy over 5.5 weeks simultaneously with 5-Fu, leucovorin and oxaliplatin. Experimental group receive 25 Gy in 5 fractions of 5 Gy over 5 days and after one week interval - consolidating chemotherapy of 3 courses of FOLFOX4. Surgery should be curried out 10-11 weeks from beginning of radiation and at least 4 weeks from the last dose of fluorouracil or radiation. The study hypothesis is that the short-course preoperative radiotherapy with consolidating chemotherapy produce at least 10% increase of the rate of R0 resection compared to preoperative chemoradiation.

Inclusion Criteria:

• Patients with unresectable primary rectal cancer or with unresectable local recurrence without distant metastases.
• WHO performance status ≤ 2.
• Lower border of tumour ≤ 15 cm from anal verge.

Exclusion Criteria:

• cardiac coronary arterial disease,
• arrhythmias,
• stroke even if they have occurred in the past and are controlled with medication