EFFECTS OF VOLUME IRRADIATED ON THE FUNCTION OF THE CANINE URETER

This study was designed to investigate the influence of the volume irr adiated on the probability of ureteral complications and to provide da ta for volume modeling, One hundred thirty-four purpose-bred beagle do gs received single intraoperative doses of 6 MeV electrons ranging fro m 12 to 54 Gy to three lengths of ureter: 2, 4 or 8 cm, The response w as evaluated by excretory urography. The ED50 was 21.9 Gy (95% CI 13.3 -30 Gy) for 8 cm 3 years after treatment, The estimated ED50's were gr eater than 43 Gy for 4 cm and 85 Gy for 2 cm, Reducing the length of u reter irradiated from 8 cm to 4 cm increased the ED50, for ureteral di lation by at least a factor of 2, while reduction from 8 cm to 2 cm in creased the ED50 by at least a factor of 4. The ED50 for renal injury secondary to stenosis was 30.5 Gy (95% CI 17.2-232 Gy)when an 8-cm fie ld was irradiated. There was a significant effect of volume irradiated on the frequency of ureteral stenosis, Reducing the length of ureter included in the treatment field should allow delivery of higher doses to tumors without increased complications, (C) 1998 by. Radiation Rese arch Society.