Diagnosis and treatment of transitional cell carcinoma of the lower urinary tract in the dog

Transitional cell carcinoma (TCC) refers to a malignant transformation of the epithelial lining of the urinary tract. Common breeds at risk are the Scottish Terrier, West Highland White Terrier, Sheltie and Beagle, typically diagnosed at the age of 8-10 years. Malignant transformation can be triggered by environmental carcinogenic substances that are excreted in the urine. Early clinical signs of TCC resemble urinary tract infections. In the advanced state of the disease, neoplastic cells may be detected in the urinary sediment in up to 30% of all cases. Ultrasonographically based transabdominal fine needle aspiration is a simple method for collecting neoplastic cell material from within the urinary bladder, but is generally not recommended due to the tumour's ability to transplant itself along biopsy tracts. Further information about urethral spread of TCC may be gained by urethrography. However, the full extent of urothelial neoplastic changes can only be appreciated during urethrocystoscopy. Information about regional lymph node involvement and metastatic spread are gained by abdominal ultrasonography, thoracic and bone radiography or by full-body CT scan. Dogs suffering from TCC are more likely to die from local disease than from systemic metastatic spread. Regional tumour resection rarely provides longer survival times compared to non-surgical treatments. Consequently, surgical treatment is only recommended in selected cases. Common non-surgical treatment options include application of non-steroidal anti-inflammatory drugs and systemic chemotherapy. Other treatment modalities, that have rarely been applied so far, include metronomic chlorambucil chemotherapy, radiotherapy, palliative transurethral diode laser resection, or intralesional Interleukin-2 injection. Median survival time over all treatment options is up to one year. Major prognostic factors are neoplastic urethral involvement and the presence of metastatic disease at the start of treatment. It should be noted that drug-resistant urinary tract infection can mimic TCC progression. In practice, canine TCC is commonly diagnosed at an advanced stage of the disease. Therapeutic decisions should be made in the view of the dog's quality of life, requiring a close follow-up and a change of treatment modalities with regard to ethical aspects and financial constraints.