Figure 4.

Hypofractionated radiotherapy (RT) results in local control of CT26 colon cancer tumors in BALB/c mice. The planning of the irradiation was conducted using a computer tomography image of the irradiation box and tumor-bearing mice with Philips pinnacle software to obtain an optimal target volume. Afterward, the dosimetry of the irradiation was performed manually with a calibrated ionization chamber. To further protect the normal tissue, the gantry of the 6-MV linear accelerator was rotated to 340°. Tumors of three anesthetized mice can be irradiated locally at once and the dose distribution (colored areas) shows that only the tumor and not the rest of the mouse is exposed to radiation (A). The tumor volumes were determined daily. Up to day 4 after the first irradiation with 5 Gy, the infiltration of immune cells in the tumors was monitored in tumors of three mice from each group (B). Hypofractionated irradiation with 2 × 5 Gy resulted in good tumor control (C); *p < 0.05, **p < 0.01; n: variable: at the starting point n = 40, with three mice less each following day per treatment group.