Survival of Rats with N29 Brain Tumours after Irradiation with 5 or 15 Gy and Immunization with IFN-gamma Secreting Tumour Cells

Intra cerebral tumours were inoculated into thebrain of Fischer-344 syngeneic rats. After one weekthey were treated with either 5 or 15 Gy of 60Cogammaradiation. The first immunization was given 1hour before the radiation treatment and then two moretimes with 14-day intervals. Immunization wasperformed with 3 x 106 radiation sterilized IFN-γsecreting tumour cells (N29) injected intraperitoneally.Neither radiation therapy with 5 or 15 Gy norimmunization with N29 cells alone had any significanteffect on the length of survival of N29 tumour bearingrats. But radiation therapy with 5 Gy combined withimmunization with IFN-γ secreting syngeneic N29 cellsresulted in 63 % complete remissions and significantly (p ≪ 0.05) increased survival for the tumour bearing rats. Corresponding combination with 15 Gy RT resulted in 50% complete remissions. There is a possibility of a synergistic effect by optimal combination of radiation therapy and immunization.