Emerging diagnostic tools and therapies for bladder cancer in canines

Bladder cancer represents 2% of all cancers in dogs. Transitional cell carcinoma (TCC) is the most common type of bladder cancer in canines and is especially malignant. Irrespective of treatment, the long-term prognosis is generally very poor. Its pathology is not well understood, and limited treatment options are available. Recent advances in identifying tumor markers have prompted the introduction of targeted therapies. In the Journal of Veterinary Sciences, the authors detail these advances while focusing on small animal oncology.¹

Risk factors such as obesity, female sex, exposure to herbicides and older topical insecticides, and certain breeds (e.g., Scottish terrier, Shetland sheepdog, beagle, and others) are thought to play a role in TTC. Clinical signs of TCC are nonspecific and can include pain or discomfort when urinating, blood in the urine, and frequent urination. These signs mimic urinary tract disorders and concurrent urinary tract infections are often seen. TCC is highly invasive and tumor growth can completely block the passage of urine. Urinary tract obstruction is often lethal and even a normal physical exam cannot rule out the presence of TCC.

Tumor cells and metabolites can be shed into the urine and these molecules may be used for tumor detection. Diagnosis of TCC involves performing a cytology of a representative sample from the tumor or from urine sediment. Researchers are investigating new tumor-specific biomarkers that can be used in the diagnostic/screening of TCC.

Treatment options for TCC are used to cause remission or provide stable disease. These options include surgery, radiation therapy, medication, or a combination of the three. Emerging localized therapies and medications are being investigated as possible treatment options.

One new possible therapy is bacillus Calmette-Guérin (BCG). BCG is commonly thought of as the tuberculosis vaccine, but it has also successfully treated nonmuscle invasive bladder cancer in humans. When tested in canines, it caused severe local inflammatory reactions.

Targeted medication therapies such as vemurafenib are also being researched. This medication showed antiproliferative effects when studied in canines with TCC. Less than half of the canines achieved partial remission and the most common adverse effect was anorexia. The study also showed the development of new tumors and resistance to therapy in some participants.

Investigators have made great progress in their understanding of bladder cancer in canines. This progress has allowed for the development of effective and noninvasive tools such as urine-based testing for the diagnosis and screening of TCC. More research is needed for the development of minimally invasive diagnostic tools which may then lead to more targeted therapies for TCC.

Isabella L. Bean is a 2022 PharmD Candidate at the University of Connecticut in Storrs.

Reference

Rasteiro AM, Sá E Lemos E, Oliveira PA, Gil da Costa RM. Molecular Markers in Urinary Bladder Cancer: Applications for Diagnosis, Prognosis and Therapy. Vet Sci. 2022;9(3):107. Published February 28, 2022. doi:10.3390/vetsci9030107