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Quick Facts at a Glance:
- More common in female dogs
- Terrier breeds more commonly affected
- Transitional cell carcinoma (TCC) is the most common type of neoplasia (cancer) encountered
- Urine cytology not very helpful as a diagnostic tool
- Ultrasonography, contrast studies and cystoscopy (scope into the bladder) are important diagnostic tools
- Tumor marker tests may be helpful screening tools for patients at risk of developing bladder cancer
- Treatment encompasses regional control of neoplastic (cancerous) growth and control of metastasis (spread)
- Palliative (painkilling) measures are often rewarding in affected patientsWhat are common clinical signs and exam findings associated with urinary bladder cancer?
The most common presenting signs are hematuria (blood in the urine), dysuria (straining to urinate), pollakiuria (frequent urination) and weight loss. On physical exam, a mass may be palpable (able to feel) in the caudal abdomen or detected on rectal examination along the urethra. Prostatomegaly (enlarged prostate), abdominal pain or a distended (large and firm) urinary bladder may be appreciated. Rarely, lameness may be present as a result of distant skeletal metastasis.
What diagnostic tests are most helpful?
Contrast cystography (x-ray study of the bladder), in which a positive contrast material is injected into the urethra (or negative contrast study in which air is injected immediately following an injection of a positive agent) can detect a filling defect in 96% of affected patients. Abdominal ultrasound is especially helpful in evaluating the integrity of the bladder wall as well as the regional lymph nodes. The presence of hydroureter (ureter over-filled with urine) or hydronephrosis (kidney over-filled with urine) due to obstruction of the outflow tract can also be assessed.
Cystoscopy (scope with a camera is inserted into the bladder) provides a non-invasive method to directly visualize the tumor and obtain samples for histopathology (biopsy) and culture (test for bacteria) in medium to large female dogs. Urethral lesions, previously very difficult to evaluate, can be directly visualized and sampled with this helpful tool.
Do these tumors metastasize frequently?
The incidence of metastasis (spread) to regional lymph nodes (nodes close to the bladder) in one study was reported to be 39% at initial diagnosis and 48% at necropsy (autopsy). Thoracic radiographs have been noted to be positive for pulmonary metastases (spread to the lungs) in 17% of patients at the time of initial diagnosis.
What about tumor marker tests?
The recent identification of proteins in the urine of dogs, which may be helpful markers for the presence of cancer, is an exciting discovery. Basic fibroblast growth factor (bFGF) is just one protein that has been reported to be found in significantly higher quantities in dogs with various forms of cancer. The bladder tumor antigen test (BTA) is a quick qualitative urine test that has been reported to demonstrate markedly high concentrations of such a protein in urinary bladder cancer. Unfortunately, this protein is also significantly elevated in other urinary tract diseases, such as urinary tract infection. Therefore, the test may be useful as an adjunct (in addition) to other diagnostics or possibly as an early screening test for geriatric animals. We highly recommend the use of this test as part of a wellness evaluation in breeds at high risk (Shetland Sheepdog, Scottish Terrier, West Highland White Terrier).
Is surgery helpful in the management of this disease?
Surgery is the mainstay of treatment for dogs with early stages (less than 2cm) of urinary bladder cancer in the apex or body of the bladder. If the trigone (area in the bladder that empties into the urethra), urethra or both urinary bladder and urethra are affected, the overall prognosis for these patients for resection and control of local disease is poor. Surgical placement of a cystotomy tube may be helpful for advanced stage patients in relieving urinary discomfort, thus avoiding complications associated with urinary tract obstruction. It is important to remember to avoid tumor seeding (spreading of neoplastic cells) when handling any tissue affected by neoplasia (cancer); these tumors shed cells easily when manipulated and tumor re-growth could be caused by “clean” tissue being touched by affected surgical instruments, needles used for obtaining urine directly from the bladder, gloves, etc.
What about other forms of local control?
Full course radiation therapy (15-18 treatments) is a very effective treatment for local tumor control; however, the scarring of the bladder that results can have significant negative impact on quality of life. Palliative (pain-relieving) radiation is well tolerated and may significantly, but temporarily, (2-4 months) improve symptoms.
Intravesical therapy (treatment directly in the urinary bladder) is rarely beneficial in veterinary medicine due to the advanced stage of the cancer at the time of diagnosis.
Is chemotherapy helpful?
There have been several chemotherapeutic agents utilized against this neoplasia. To date, none have proven to be reliably effective against advanced stages of urinary bladder cancer in the dog. However, there are ongoing studies recently, which suggest that mitoxantrone (chemotherapy agent) combined with piroxicam (or feldene-anti-inflammatory agent) may afford prolonged comfortable survival time.
What role does piroxicam play in the management of this disease?
Piroxicam (feldene) is a non-steroidal anti-inflammatory agent, has been shown to reduce the severity of clinical signs associated with urinary bladder and urethral cancer. In some patients, long-term use may result in tumor regression, most likely due to the angiogenesis inhibiting (prevention of blood vessel growth) effects of this drug. The alleviation of dysuria (painful urination) in affected patients makes this therapeutic option very attractive for clients seeking to obtain additional quality time with their pet. This palliative measure can therefore be a viable option for non-resectable urinary tract neoplasia.
© Reproduced with permission from www.vrcc.com courtesy of Dr Robyn Elmslie
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