TOLERANCE OF THE BLADDER TO INTRAOPERATIVE RADIATION IN A CANINE MODEL - A 5-YEAR FOLLOW-UP

Purpose: Late effects of intraoperative radiation therapy (IORT) on bl adder were investigated in a canine model. Methods and Materials: Afte r laporatomy and cystotomy in adult female foxhounds weighing 25-35 kg , 12 MeV electrons were delivered intraoperatively to a 5 cm circular bladder held which included the trigone and both uretero-vesicle junct ions. Each animal received doses of 0, 20, 25, 30, 35, or 40 Gy. All t he dogs were followed 5 years postoperatively. An unoperated dog recei ving no surgery or radiation treatment was followed as a control. Clos e clinical monitoring was performed with regular cystometrics and intr avenous pyelography. Animals were killed as scheduled with complete ne cropsies, including histopathology, with special attention to genitour inary structures. Results: There were no acute or late bladder complic ations detected clinically in any animal. The dog receiving 30 Gy IORT developed rhabdomyosarcoma in the treatment field at 58 months. On fo llow-up testing over 5 years, there was no loss of bladder contractili ty on cystometry, and mild changes in the ureters on intravenous pyleo graphy when animals receiving IORT were compared with baseline pretrea tment values or with control animals. Histologically, a difference was evident between irradiated and unirradiated animals, but the changes were not clearly dose-related. Conclusion: Intraoperative radiation th erapy may by safely delivered to the canine bladder with few acute or chronic complications. It is an approach which has potential for clini cal use and should continue to be explored in human clinical trials.