Tumor response to 6.3 MeV fast neutrons generated by U-120 cyclotron was assessed. The study included: 26 patients with locally advanced breast cancer, who received neutron therapy in the regimen of high-dose daily fractions, followed by surgery; 41patients with head and neck cancer and 44 patients with musculoskeletal system cancer. The devised method of 6.3 MeV neutron therapy given in high-dose fractionation regimen resulted in complete tumor response compared to the standard photon therapy.