[en] A randomized study was performed to evaluate 5 years results of combined treatment of patients with ray-resistant cancer of large intestine in correlation with post-radial changes in dissected tumours. Experiments were carried out in groups of patients exposed to different preoperative ray doses with or without antioxidant supply. Summer local dose on the tumour was 20 Gy (single dose was 5 Gy) or 30 Gy (single dose was 6 Gy). The data revealed some histological or histochemical post-radial differences in dissected tumors, but these changes were not connected with radiation dose or antioxidant supply. It was concluded that post-therapeutic changes in tumor after radial therapy could not be used for assessment of degree of risk of metastasis