Radiation therapy as a treatment for urinary obstruction secondary to urothelial carcinoma in dogs

BACKGROUND: Urothelial carcinoma (UC) is the most common urinary bladder tumor in dogs, often invading and involving the bladder wall, trigone, urethra, and prostate and can lead to obstruction of urine outflow at the level of the ureters or urethra. HYPOTHESIS/OBJECTIVES: To describe the outcome of dogs with UC presenting with urethral or ureteral obstruction treated with radiation therapy (RT). ANIMALS: Twenty-five client-owned dogs treated with RT. METHODS: A retrospective analysis was conducted. Overall survival, time to first event, and restoration of patency were evaluated by obstruction location and radiotherapy protocol. RESULTS: Overall obstruction relief was achieved in 15/25 (60%) dogs. Definitive intent protocols showed significantly longer time to obstruction relief (median 8 vs 4 days; range 2-10 vs 2-7 days; P = .02), however, had higher overall efficacy (83% vs 53%) and survival times compared to palliative intent protocols (P = .01). Dogs that had relief of obstruction regardless of RT intent received a significantly higher total dose compared to those that did not experience relief (median 36 Gy vs 8 Gy; range 12-57 vs 6-24 Gy; P < .001). Median overall survival time was 134 days (range 6-969 days) and time to first event was 107 days (range 4-695 days). Location of obstruction did not significantly improve survival or time to obstruction relief. Relief was temporary for 27% of unobstructed dogs, and re-obstruction was seen at a median of 14 days (range 5-33 days). CONCLUSIONS AND CLINICAL IMPORTANCE: Radiation therapy is a viable treatment option for relieving urinary obstruction secondary to UC. Radiation therapy protocol should be determined based on the dog's clinical signs, ability to medically manage obstruction, and therapeutic goals of the owner.