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 bladder we Methods and Materials: After 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 junctions. Each animal received doses of 0, 20, 25, 30, 35, or 40 Gy. All the dogs were followed 5 years postoperatively. An unoperated dog receiving no surgery or radiation treatment was followed as a control. Close clinical monitoring was performed with regular cystometrics and intravenous pyelography. Animals were killed as scheduled with complete necropsies, including histopathology, with special attention to genitourinary structures. Results: There were no acute or late bladder complications detected clinically in any animal. The dog receiving 30 Gy IORT developed rhabdomyosarcoma in the treatment field at 58 months. On follow-up testing over 5 years, there was no loss of bladder contractility on cystometry, and mild changes in the ureters on intravenous pyleography when animals receiving IORT were compared with baseline pretreatment 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 therapy may by safely delivered to the canine bladder with few acute or chronic complications. It is an approach which has potential for clinical use and should continue to be explored in human clinical trials.