Most dogs with urethral transitional cell carcinoma (TCC) die from progressive local disease. Treatment options for the urethra include palliative stenting, trans-urethral resection, vagino-urethroplasty , chemotherapy and radiation therapy (XRT). Various options for XRT to treat lower urinary tract carcinomas have been described. Reports dating back to 1987 show that XRT has been used successfully to control canine bladder TCC , however irradiation of lower urinary tract tumors poses several uniquechallenges. These include the difficulty in tumor localization and proximity of the tumor to dose limiting structures such as the ureters and colon. Complications of therapy include cystitis and fibrosis as well as irritation to surrounding organs. Thesesequelae can significantly detract from the patients' quality of life and successful use of XRT for the treatment of canine carcinoma requires careful delivery of the radiation dose. Factors to consider when designing radiation protocols include the volume of bladder/urethra to be irradiated, the total dose to be delivered, the dose per fraction to be used and the dose to surrounding tissues.
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