Bladder cancer in dogs and cats is a tumor of the cells lining the organ that collects urine excreted by the kidneys. The most common type of bladder cancer is transitional cell carcinoma. Other less common cancers include adenocarcinomas, squamous cell carcinomas, and fibromas. Over time, the malignant tumor grows and causes urinary obstruction, and spreads to the lymph nodes, lung, bones, and other areas of the body.
While the exact cause of cancer development is not known, genetic and environmental factors are believed to be involved. While smoking is involved in bladder cancer development in people, it is thought that exposure to second-hand smoke may play a role in dogs as well. Certain flea dips, as well as inert ingredients in pesticides and insecticides could also be factors involved with an increased risk of bladder cancer. Certain dog breeds have with a higher incidence of bladder cancer, such as Scottish Terriers, West Highland White Terriers, Shetland Sheepdogs, and Beagles.
The most common symptoms of bladder cancer in pets are the presence of blood in the urine, frequent urination with straining, and painful urination. It is important to differentiate bladder cancer from a urinary tract infection and urinary tract stones, which may cause similar symptoms.
Veterinarians often need to run several tests to differentiate bladder cancer from other causes of urinary tract inflammation. CBC/chemistry blood tests, urine analysis, X-rays, and an ultrasound can help sort out the various possible causes of clinical signs and document the spread of cancer. A urine bladder tumor antigen test has been developed and is an excellent screening test to rule out bladder cancer. If a bladder tumor antigen test is positive, then further ultrasound and tissue biopsy will be necessary to make a definitive diagnosis and guide specific therapy. Based on results of the biopsy, and evaluating for the spread of cancer to lymph nodes and other organs, bladder cancer is then staged so that the best treatment is utilized. These diagnostic tests may be repeated during the course of therapy to document if treatment has been effective or needs to be changed.
Since bladder cancer in pets grows quite rapidly and is often advanced at the time of diagnosis, complete surgical removal of the mass is not often possible. Since this cancer frequently involves an area of the bladder known as the trigone (where the ureters and urethra empty urine into the bladder), surgical debulking may not be possible. In these cases, remaining options include radiation of the affected areas of the bladder or chemotherapy utilizing a single or sequential group of drugs. Since most bladder cancers involve the trigone area of the bladder, and potential irritation to surrounding organs, radiation is not often used in clinical practice. Using chemotherapeutic drugs such as Adriomycin, Vinblastine Cisplatin, and Carboplatin has also yielded disappointing results. In recent years, however, the use of the non-steroidal anti-inflammatory drug (NSAID) Piroxicam has produced surprising and significant positive results when used in dogs with transitional cell carcinoma of the bladder. When combined with the IV chemotherapy drug Mitoxantrone, treatment efficacy with Piroxicam resulted in even better results than using Piroxicam alone. Many veterinary institutions often run clinical drug trials for dogs with bladder cancer, so it is always best to check with these facilities to see if your pet may be eligible for these trials.
The prognosis for pets with bladder cancer is guarded, with a cure unlikely given the high stage of development at the time of presentation. Pets with localized disease in the wall of the bladder will have a better prognosis for palliative relief than pets with cancer that has spread to the lymph nodes, prostate, bone, or lung. Survival is also affected by tumor growth rate, as well as location within the bladder wall.
Studies at Purdue University Veterinary School of Medicine have shown that while most dogs treated with chemotherapy may live somewhat over four months, dogs treated with Piroxicam often live over six months. The response will vary greatly from dog to dog, with some dogs living more than two years. Remission may be achieved in one-third of dogs treated with both IV Mitoxantrone and Oral Piroxicam, with a median survival rate of 8-10 months.
Because of the location and rapid growth of many bladder cancers, urinary obstruction with potential toxic buildup of waste products and shock is always possible. If urinary obstruction occurs, various surgical procedures including stents and cystostomy tubes placed into the bladder may be required. Dogs with bladder cancer are also prone to bacterial infections. Frequent urine analysis, bacterial culture, and oral antibiotics may be needed in these pets, especially if clinical signs suddenly worsen. Non-steroidal anti-inflammatory drugs (NSAIDs) like Piroxicam may sometimes cause lethargy, loss of appetite, vomiting, and dark tarry feces. In these cases using gastrointestinal protectant drugs such as oral Pepcid or Prilosec may help, or it may be necessary to stop the drug. In some of these cases, alternative NSAIDs such as Metacam, Previcox, or Rimadyl may be acceptable alternatives for palliative symptom relief in dogs. Tramadol can be used for both cats and dogs.