Urinary bladder cancers are more common in female dogs, with Scottish Terrriers, West Highland White Terriers, Shetland Sheepdogs, and Beagles being overrepresented. Transitional cell carcinoma (TCC) is by far the most common type of bladder neoplasia (cancer) encountered in dogs.

 

Causes of this type of cancer

  • In people smoking is the single greatest risk factor for the development of bladder cancer. Exposure to certain chemicals (aromatic amines, chemicals used in the dye industry, and chemicals used in textiles, hair coloring, paints and printing) has a greater risk of bladder cancer than the general population.

Common clinical signs of urinary bladder cancers

  • The most common presenting signs are hematuria (blood in the urine), dysuria (straining to urinate), pollakiuria (frequent urination), and weight loss. On physical examination, a mass may be felt in the abdomen or detected on rectal examination along the urethra. Prostatomegaly (enlarged prostate), abdominal pain, or a distended (large and firm) urinary bladder may be noticed. Rarely, lameness may be present as a result of spread of the cancer to the bones of the spine.

How is this cancer diagnosed?

  • The Bladder Tumor Antigen test may be useful as a screening test in middle aged dogs (especially in breeds that are predisposed to getting this type of cancer). This urine test is most helpful when there are no signs present; it is a very good screening test. This means that if the test is negative, it is very unlikely your dog has this cancer.
    However, a positive test requires additional diagnostics to confirm a diagnosis of bladder cancer.
    • Abdominal ultrasound is helpful in evaluating the bladder wall as well as the regional lymph nodes for the presence of a mass or thickened bladder wall
    • Contrast cystography is a test that can detect a filling defect (mass) in 96% of patients affected by bladder cancers. A contrast cystography is an x-ray study of the bladder in which a contrast agent or air is injected into the bladder.
    • Cystoscopy (camera inserted into the bladder) provides a minimally invasive method to directly visualize the tumor and obtain samples for biopsy and culture in female dogs.
    • Obtaining a diagnosis of this type of cancer typically involves getting a sample of the tumor. This can be achieved by either a surgical biopsy (not appropriate for all patients) or cytologic evaluation. Cytologic evaluation involves passing a urinary catheter into the bladder and gently rubbing the tip of the catheter along the tumor to extract some of the cells for analysis.  Cystocentesis (bladder puncture) should never be performed to obtain a cytologic sample or urine sample in patients suspected of having a bladder tumor due to the potential of tumor seeding (tumor growth on the skin or in the abdomen at the site of the cystocentesis)
  • The incidence of spread (metastasis) to the lymph nodes near the bladder in one study was reported to be 39% at initial diagnosis and 48% at autopsy. Chest x-rays have been noted to be positive for spread to the lungs in 17% of patients at the time of initial diagnosis.

How is this cancer treated?

  • There have been several chemotherapeutic agents utilized to effectively treat this cancer. Studies suggest that mitoxantrone or vinblastine (both injectable chemotherapy agents) combined with piroxicam (or Deramaxx or Metacam) (anti-inflammatory agents) may increase both quality and quantity of life.
  • Piroxicam (Feldene) is a non-steroidal anti-inflammatory agent (NSAID) that has been shown to help animals feel better –have less blood in the urine, strain less and urinate less frequently---and allow them to live longer. In some patients, long term use even may result in the tumor getting smaller.
  • Surgery may be an option for your dog, depending on the location of the tumor. Surgery is most appropriate for dogs with early stages of urinary bladder cancers (small tumors) in the apex or body of the bladder. If the tumor is in the trigone (area of the bladder that empties into the urethra), urethra, or both urinary bladder and urethra, surgery is more difficult. Both urethral and ureteral stents can be placed in animals with advanced stages of disease to help relieve discomfort associated with a urinary tract obstruction or to relieve an obstruction preventing urine from reaching the bladder from the kidney. These stents can prolong a good quality of life for quite a long time.
  • Laser therapy is also available as a means of locally controlling the cancer and is quite effective in many dogs in relieving the clinical signs (straining to urinate and increased frequency of urination) for quite a long time
  • Full course radiation therapy (15-18 treatments) is a very effective treatment for local control, however, 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, improve symptoms.
  • Intravesicular therapy (treatment directly into the urinary bladder) can be used but its effectiveness in veterinary medicine is currently unknown.


What is the prognosis for dogs / cats with this cancer?

  • Dogs that are untreated may only survive for a few months, the addition of piroxicam alone can help improve both quality and quantity of life for around 9 months while the addition of an injectable chemotherapy (mitoxantrone or vinblastine) can extend quality of life for an additional 3-6 months. The use of either surgical stents (urethral and/or ureteral) or laser therapy can extend quality of life an additional 5-7 months.


What new diagnostics, therapy, are on the horizon for this cancer?

  • The use of intra-arterial chemotherapy (chemotherapy delivered directly into the artery that supplies the tumor with blood) through a small surgically placed catheter is being evaluated as a way to deliver higher doses of chemotherapy to the bladder tumor without causing side effects to the rest of the dog.

Contributed by: Veterinary Cancer Center