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 the brain of Fischer-344 syngeneic rats. After one week they were treated with either 5 or 15 Gy of ⁶⁰Co-gamma radiation. The first immunization was given 1 hour before the radiation treatment and then two more times with 14-day intervals. Immunization was performed with 3 times 10⁶ radiation sterilized IFN-gamma secreting tumour cells (N29) injected intraperitoneally. Neither radiation therapy with 5 or 15 Gy nor immunization with N29 cells alone had any significant effect on the length of survival of N29 tumour bearing rats. But radiation therapy with 5 Gy combined with immunization with IFN-gamma secreting syngeneic N29 cells resulted 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.