Urinary bladder cancer accounts for approximately 2% of all reported malignant cancers in the dog. The most common type of bladder cancer is TCC (transitional cell carcinoma), however, we can also see squamous cell carcinoma, lymphoma, rhabdomyosarcoma, undifferentiated carcinoma, hemangiosarcoma, etc.
TCC is most commonly located in the trigone region of the bladder (see image courtesy of Vet Surgery Central). It can also involve the urethra or the prostate (if the patient is male). Due to the location of the tumor, it can cause partial or complete urinary obstruction, making it difficult or impossible to urinate.
Proper initial work up not only includes an accurate diagnosis and full blood work, but also 3-view chest x-rays and full abdominal ultrasound to determine if cancer has metastasized. Metastasis will affect which treatment options are reasonable for the patient.
Which Dogs Develop Bladder Cancer?
Risk factors include female sex, obesity, lawn chemicals, possibly cyclophosphamide exposure, breed, and older generation flea control products (topical flea and tick dips which aren't used anymore).
One study showed that Scottish terriers exposed to lawn herbicides or herbicides and insecticides had an increased risk of developing TCC (not insecticides alone).
Scottish terriers that ate vegetables at least 3 times per week (along with their normal diet) had a reduced risk of TCC (carrots were the most frequently fed vegetable in the study).
Scottish terriers - 18 times increased risk of TCC than other dogs
Sheltie - 4.46 times increased risk
Beagle - 4.16 times increased risk
Wire-haired fox terrier - 3.2 times increased risk
West Highland white terrier - 3 times increased risk
The remaining breeds have a less than 1 time increased risk - Miniature schnauzer, miniature poodle, Doberman pinscher, Labrador retriever, golden retriever, German shepherd.
Common Signs of Bladder Cancer
Signs of bladder cancer include increased urgency to urinate, painful urination, bloody urine, and urinating small amounts of urine at a time.
A dog may have all of these signs or just one or none of them. Urinary signs may be present for weeks to months (sometimes an accurate diagnosis takes quite some time because dogs are misdiagnosed with a urinary tract infection).
At the clinic, the only sign might be increased red blood cells or white blood cells on a urinalysis.
If a dog is suspected to have a urinary tract infection but the "infection" is not resolving with appropriate treatment, ultrasound of the bladder should be the next step to determine if a mass is present.
In many cases, ultrasound is used in order to obtain a urinalysis (which is part of routine labs for any patient) and a bladder mass is found incidentally. Since not every clinic has access to ultrasound, this is not always possible.
How Do We Make A Diagnosis?
There are many ways to make a diagnosis. In some cases, the first option that we try doesn't work out, so we have to try a second option. Every case is different; the vet/oncologist will make their decision based (in part) on the location and size of the bladder mass.
(1) Free catch urinalysis with cytospin
This technique is nice because it's non-invasive and can often achieve a diagnosis if the tumor is very large or if it involves the urethra. Your dog would urinate in a cup, the vet staff would spin down the urine in small tubes, and if successful, each tube would have a small pellet of cancer cells at the bottom. The urine would be pipetted away from the cells, the cells would be smeared on glass slides, and sent to the lab for evaluation (sometime a preliminary diagnosis can even be made in house if you're seeing an oncologist).
(2) CADET BRAF Assay
This newer test involves collecting a relatively large sample of urine and sending it to a lab for evaluation. Special collection tubes are needed; the urine can be stored in the fridge for a few days if your dog doesn't urinate enough at the vet clinic. About 85% of TCC (and urothelial carcinoma) will have mutated BRAF. If this test is "positive" you have your diagnosis. Benefit - not invasive. Drawback - results take longer than cytology (in example 1), your vet clinic may not have the special tubes in stock, if the test is negative your dog may still have TCC.
(3) For small tumors...
If your dog's tumor is small or located in a difficult area of the bladder to sample, options for diagnosis include (a) cystoscopy - using anesthesia and a scope to obtain a biopsy sample, (b) aspirate the mass - sedate the patient and aspirate the mass with a small needle, (c) catheterization - sedate the patient and use a catheter to poke at the mass and dislodge cells in to urine, which is collected and spun down (as in example 1).
Every situation is different, so your vet/oncologist would have to discuss each with you and decide on the best course of action.
Treatment Options For Transitional Cell Carcinoma (TCC)
(1) Surgery - In cases where there is no metastasis and the bladder tumor is small and located in the apex of the bladder (the opposite end from the trigone), surgery may be considered. Surgery is not considered curative and the tumor is expected to return, but in my experience, does allow for 6-8 months before tumor recurrence is typically noted.
A fairly recent study from Colorado State showed that 37 dogs undergoing surgery (partial cystectomy) and daily piroxicam therapy (NSAID) had a median survival time (half lived longer and half shorter) of 772 days, which is excellent for this disease.
(2) Medical Therapy - Treatment with chemotherapy plus piroxicam (or other mostly Cox2 selective NSAID) is considered the mainstay of treatment for TCC. The goal of treatment is to achieve remission (partial or complete) or stable disease. We typically feel that with treatment, the patient will achieve an average survival of 6-12 months. Chemotherapy options typically include vinblastine, mitoxantrone, carboplatin, and sometimes Palladia. For TCC, we typically treat with one protocol (chemotherapy agent) until the patient fails, then move to the next.
Note: some dogs can achieve a partial or complete remission with piroxicam alone if their tumor is small.
Cases with urethral involvement present more of a challenge. If the tumor becomes even the smallest degree larger, the patient may be completely obstructed and unable to urinate (necessitating a stent or temporary catheter or euthanasia); for patients with urethral involvement the prognosis is typically closer to 6 months if response to treatment is noted.
(3) Radiation Therapy - Numerous radiation therapy protocols have been studied and used for TCC in dogs. Many appear successful. The type of protocol chosen for an individual patient depends on that patient's specific situation, what type of radiation is available in the area, and potential financial limitations of the family.
Radiation can be used in cases of complete urinary obstruction; in this situation, the patient would need to remain catheterized (to allow for urination) while waiting to determine if treatment was successful in relieving the obstruction.
After radiation, it is ideal to continue treatment with medical therapy in an attempt to kill additional cancer cells and delay metastasis.
(4) Stenting - Placing a stent is typically done as an emergency procedure to resolve urinary obstruction. If a patient cannot urinate due to a tumor in the urethra, a stent can provide temporary relief. Unless tumor growth is slowed using medical therapy (chemo + NSAIDs) tumor will grow through the stent and the patient will re-obstruct. This can happen in a few months.
(5) Pain relief, etc. - Urinary tumors are uncomfortable. These patients always feel like they have to urinate. Piroxicam is an anti-inflammatory (NSAID), which can alleviate some of the discomfort. I would also consider adding an additional medication such as gabapentin to further increase comfort. If there is a large amount of hematuria (bloody urine) your vet may suggest Yunnan Baiyao, a Chinese herb which may help reduce bleeding.
(6) Metronomic chemotherapy - Low dose oral chemotherapy using chlorambucil is a less expensive alternative to traditional chemotherapy, which also appears to have benefit. One study showed that 70% of patients achieved a partial response or stable disease for a median (half did better and half didn't) length of control of 119 days.
If your dog has signs of a urinary tract infection that are not resolving with antibiotics, have a bladder ultrasound performed to make sure a bladder mass isn't present. An early diagnosis will give the best chance at the longest survival and the most treatment options.
Have questions about this article? Reach out!
Dr. Lori Cesario
Board Certified Veterinary Oncologist
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