The combined effect of the irradiation with a proton pencil scanning beam (PBS) at a total dose of 80 Gy and neutron radiation at a dose of 5 Gy on the growth of solid Ehrlich ascites carcinoma (EAC) and the remote effects in tumor-bearing mice was studied. Combined irradiation of mice with neutrons before and after irradiation with PBS, as well as irradiation only with PBS, effectively suppressed the growth of solid EAC within 1 month. In terms of the frequency and severity of radiation-induced skin reactions of mice observed 15-40 days after therapy, neutron irradiation after the irradiation with PBS showed better values of these parameters as compared to only PBS; however, exposure to neutrons before PBS was more damaging as compared to the other two options. It was also shown that the tumor relapse rate in the groups of animals with combined irradiation was higher, and the total lifespan was lower than the group of mice irradiated with PBS alone.
Keywords: Ehrlich ascites carcinoma; hypofractionation; mice; neutron radiation; proton pencil beam scanning; tumor relapses.