Successful Management of Incompletely Resected Transitional Cell Carcinoma with Sorafenib Tosylate in a Dog.

Most urinary bladder (UB) tumors are malignant, and transitional cell carcinoma (TCC) is the most common neoplasm affecting the UB in dogs. Sorafenib may be a potential therapeutic agent for canine TCC. A 12 yr old spayed female Maltese dog weighing 3.6 kg and with a history of hematuria was referred for a suspected UB tumor. Abdominal ultrasonography revealed a UB mass attached to the cranioventral wall. The remaining abdominal examinations, including that of the lymph nodes, were unremarkable. Ultrasound-guided traumatic catheterization of the UB mass was performed, and the cytological evaluation of the UB mass indicated TCC. Excision was performed by partial cystectomy, and histopathology confirmed TCC, although the tumor had infiltrated the surgical margins. A chemosensitivity assay was conducted using tissue from the excised tumor. Sorafenib tosylate, a tyrosine kinase inhibitor, showed the greatest effect in the chemosensitivity assay. Therefore, adjuvant chemotherapy with sorafenib tosylate and piroxicam was administered postoperatively. The dog lived without any clinical signs, including hematuria or tumor relapse, for more than 2 yr after the surgery. This is the first report of successful long-term management of TCC with sorafenib tosylate in a dog.