Objective—To determine the antitumor effects and toxicoses of metronomic oral administration of a low dose of chlorambucil in dogs with transitional cell carcinoma (TCC). Design—Prospective clinical trial. Animals—31 client-owned dogs with TCC for which prior treatments had failed or owners had declined other treatments. Procedures—Chlorambucil (4 mg/m², PO, q 24 h) was administered to dogs. Before and at scheduled times during treatment, evaluations of dogs included physical examination, CBC, serum biochemical analyses, urinalysis, thoracic and abdominal imaging including cystosonography for measurement of TCCs, and grading of toxicoses. Results—29 of 31 dogs had failed prior TCC treatment. Of the 30 dogs with available data, 1 (3%) had partial remission (≥ 50% reduction in tumor volume), 20 (67%) had stable disease (< 50% change in tumor volume), and 9 (30%) had progressive disease (≥ 50% increase in tumor volume or development of additional tumors); 1 dog was lost to follow-up. The median progression-free interval (time from the start of chlorambucil treatment to the day progressive disease was detected) for the dogs was 119 days (range, 7 to 728 days). The median survival time of dogs from the time of the start of chlorambucil treatment was 221 days (range, 7 to 747 days). Few toxicoses were detected; chlorambucil administration was discontinued because of toxicoses in only 1 dog. Conclusions and Clinical Relevance—Metronomic administration of chlorambucil was well tolerated, and 70% of dogs had partial remission or stable disease. Metronomic administration of chlorambucil may be a treatment option for dogs with TCC.

Objective—To determine uroplakin III expression, potential etiologic factors, biological behavior, and treatment response of transitional cell carcinoma (TCC) in the abdominal wall (ABWTCC) in dogs. Design—Retrospective case series. Animals—24 dogs with TCC of the urinary tract that also had histopathologic confirmation of ABWTCC. Procedures—Medical records, histologic slides, radiographs, and ultrasonographic images of dogs with ABWTCC between July 1, 1985, and December 31, 2010, were reviewed. In available tissue specimens, immunohistochemistry was used to detect uroplakin III expression in the ABWTCC and in the primary tumor. Results—The ABWTCC lesions ranged from < 2 to > 20 cm in diameter. Uroplakin III was expressed in 19 of 20 primary tumors and 17 of 17 ABWTCCs. Transitional cell carcinoma in the abdominal wall developed significantly more often in dogs that had undergone cystotomy (18/177 [10.2%]) than in those that had not (6/367 [1.6%]). In 1 dog that had not undergone cystotomy, TCC had invaded through the urinary bladder wall and spread down the median ligament to the abdominal wall. None of 18 dogs that received anticancer drugs had remission of the ABWTCC once clinically detected; median survival time after ABWTCC detection was 57 days (range, 0 to 324 days). Conclusions and Clinical Relevance—Results suggested that ABWTCC is uncommon, but once TCC becomes established and clinically detectable in the abdominal wall, it carries a poor prognosis. It is crucial to minimize risk of TCC seeding at surgery. Percutaneous sampling of TCC should be avoided. Uroplakin III is commonly expressed in ABWTCC.