Bladder Cancer in Dogs: A Guide to Transitional Cell Carcinoma (TCC)

Hearing a diagnosis of bladder cancer in dogs can be distressing as a dog parent, but integrative veterinarian Dr. Julie Buzby is here to help. Learn the signs, diagnosis, treatment, and prognosis for the most common type of bladder cancer, transitional cell carcinoma in dogs. Armed with that information, you will be ready to help and support your canine companion in his or her battle with bladder cancer.

Sally was a twelve-year-old female spayed Scottish Terrier who had been the picture of health. But now she was asking to go outside more often, straining to urinate, and had left a large puddle of bloody urine on the kitchen floor. Her family was worried, so they brought her to see me.

I diagnosed my Scottie patient with what I thought was going to be a run-of-the-mill urinary tract infection. However, unlike most UTIs that significantly improve within a few days of starting antibiotics, Sally’s problems persisted. After a urine culture, which ruled out ongoing bacterial infection, I moved on to a bladder ultrasound to try to get to the root of my canine patient’s problem.

Unfortunately, the ultrasound revealed a large mass in the dog’s bladder that extended down into the urethra. So I had to break the devastating news to her family—their dog had bladder cancer.

What are the types of bladder cancer in dogs?

The term “bladder cancer” refers to any sort of cancer that grows in the urinary bladder.

Of the different types of lower urinary system cancers in dogs, transitional cell carcinoma (TCC) is by far the most common. It accounts for up to 90% of all bladder tumors.

The other 10% consist of many other types of tumors, including:

• Leiomyosarcoma
• Adenocarcinoma
• Lymphoma in dogs
• Fibrosarcoma
• Squamous cell carcinoma
• Hemangiosarcoma in dogs
• Infiltrative prostatic carcinoma

What is a transitional cell carcinoma in dogs?

Since the vast majority of bladder tumors are transitional cell carcinomas, let’s take a closer look at this tumor type.

In this case, the tumor arises from transitional cells, which are the specialized cells that normally line the inside of the bladder. When some of these cells become neoplastic (i.e. cancerous), the result is a transitional cell carcinoma. Sometimes a TCC is also called a urothelial carcinoma (UC).

The most common place for a transitional cell carcinoma to occur is in the trigone region of the bladder. This is the area at the neck of the bladder where the ureters—which connect the kidneys to the bladder—enter the bladder and the bladder narrows into the urethra. Unfortunately, a tumor in this area cannot be removed surgically.

Which dogs tend to get bladder cancer?

There are several factors that may make a dog more likely to develop bladder cancer. In general, TCC is most common among middle-aged or older female dogs. However, it can occur in dogs of any age and gender.

While transitional cell carcinoma can occur in any breed, certain dog breeds are at a higher risk. There is likely a genetic predisposition for developing TCC, as evidenced by Scottish Terrier dogs. Scotties are twenty times more likely to develop TCC than other breeds with the same environmental risk factors.

Breeds of dogs at risk for TCC include:

• Scottish Terriers (the most common breed to be diagnosed with TCC)
• Shetland Sheepdogs
• West Highland White Terriers
• Fox Terriers
• Airedales
• Beagles
• Collies

Dogs that have been exposed to herbicides and insecticides also have a higher risk of developing TCC. Obesity is also a risk factor. It is thought that components of these herbicides and insecticides accumulate in fat tissue.

Chronic and recurrent urinary tract infections (UTIs in dogs) also increase the risk of developing transitional cell carcinoma. Urinary tract infections are much more common in female dogs than male dogs. This may explain why females also seem to develop TCCs more frequently than males.

Administration of the chemotherapy agent Cyclophosphamide also has been associated with a higher risk of developing TCC.

What are the symptoms of bladder cancer in dogs?

As demonstrated by Sally’s story, the signs of bladder cancer and a UTI are often very similar. The symptoms might include:

• Straining to urinate
• Urinating more frequently
• Urinary accidents
• Blood in the urine

In more advanced cases, a bladder tumor may cause a complete obstruction of the urethra so the dog is unable to urinate. The bladder may even rupture.

If the tumor has metastasized (i.e. spread) to the local lymph nodes, the vet might notice enlargement of the inguinal or sublumbar lymph nodes.

Although it is a rare occurrence, TCC can trigger hypertrophic osteopathy. This is a reaction of the periosteum (outer portion of the bone) leading to bone thickening and pain. It most commonly occurs in the lower portion of the legs.

How is bladder cancer diagnosed?

As we established, urinary tract infections are much more common than bladder tumors, and the signs are almost identical. So unsurprisingly, a dog who actually has a bladder tumor often initially gets a presumptive diagnosis of a UTI.

To further complicate matters, many dogs with a bladder tumor will have a concurrent urinary tract infection. So when the vet sees blood, bacteria, and white blood cells in the urine, he or she would understandably initially diagnose this as a UTI rather than having a high suspicion of bladder cancer.

Many dogs with bladder tumors will initially improve on antibiotics, especially if the tumor is small and in the early stages. The clinical improvement may be due to the anti-inflammatory effect of some antibiotics on the bladder. It can also be due to the fact that some dogs do have a concurrent UTI that is contributing to the signs.

As in my Scottie patient’s case, the vet may first suspect bladder cancer when an older female dog has recurrent urinary issues that are not improving or quickly return despite appropriate antibiotic therapy. In many cases, the vet will be able to visualize a mass on ultrasound. However, the vet will need to be careful when interpreting the ultrasound. It is easy to mistake inflammation of the bladder wall for a tumor, especially if the bladder is small and fairly empty.

Avoid aspirates

Most of the time when the vet finds a tumor somewhere in the body, he or she will recommend an aspirate. This involves having the vet place a needle into the tumor, apply suction to remove some of the cells, and examine the cells under the microscope.

However, vets don’t recommend that sort of aspirate for suspected bladder cancer. There have been reports of “tumor seeding” with TCC after an aspirate. In other words, tumor cells followed the tract of the needle and started to grow throughout the abdomen. Therefore, other methods are recommended for collecting samples for diagnostics.

Cystoscopic biopsy

Instead of doing an aspirate, the vet can obtain a biopsy from the tumor through a cystoscope. This is a special scope with a camera that the vet slides up the urethra and into the bladder. As with aspiration, a surgical biopsy runs the risk of seeding tumor cells through the abdomen, so it is typically not a good idea.

Traumatic catheterization

Identifying neoplastic transitional cells in a urine sample is another useful diagnostic option, especially if the vet collects the sample through “traumatic catheterization.” Traumatic catheterization involves passing a urinary catheter and intentionally irritating the bladder tissue and tumor. This causes the tumor to release cells into the urine.

It is important to note that interpreting the traumatic catheterization sample is best left to a veterinary pathologist. This is because chronic inflammation of the bladder wall can damage the cells and make them appear neoplastic. A board-certified veterinary clinical pathologist should be able to distinguish between cancer and inflammation. But most general practice vets don’t have that level of expertise with cytology.

CADET® BRAF test

Recently, a new test has become available that makes the diagnosis of TCC much easier for the veterinarian and the patient. The test is called a CADET® BRAF test. Eighty-five percent of TCC tumors have a genetic mutation called the BRAF mutation. Finding cells with the BRAF mutation on a free catch urine sample can confirm a diagnosis of TCC. However, since only 85% of TCC tumors carry the BRAF mutation, it won’t find every case of TCC.

The good news is that now there is a CADET BRAF-PLUS test. It is able to detect approximately two-thirds of the TCCs the regular CADET BRAF test misses. Together, the BRAF and BRAF-PLUS can find 95% of TCCs. The BRAF test is easy to perform, non-invasive, and has a high chance of correctly identifying TCC so it is quickly becoming popular with veterinarians and dog parents.

What is the treatment for bladder cancer?

Once the vet has diagnosed your dog with bladder cancer, he or she will discuss the treatment options.

Surgery

If the tumor is located in the apex (i.e. top) of the bladder, a skilled surgeon may be able to remove a portion of the bladder wall along with the tumor. However, since most TCCs occur in the neck of the bladder where the ureters and urethra are located, surgical removal is usually not an option.

If surgery is not an option, or the vet performs surgery and there is evidence of spread to other parts of the body, medical therapy can extend a dog’s life significantly.

Piroxicam

Nonsteroidal anti-inflammatory medications, especially Piroxicam, are the mainstay of treatment for TCC. Piroxicam reduces the tumor volume overall and reduces the clinical signs associated with bladder tumors.

Chemotherapy

Dogs may sometimes need chemotherapy in combination with Piroxicam or instead of Piroxicam. It is best to consult with a board-certified veterinary oncologist to determine which chemotherapy agents would be best based on your dog’s history, overall health, the location of the tumor, and other factors. In general, the more common chemotherapeutic agents for TCC are Mitoxantrone or doxorubicin. Palladia is also another option.

Researchers at Iowa State University College of Veterinary Medicine also are studying a novel delivery system for chemotherapy that uses nanoparticles. It would allow veterinarians to effectively deliver chemotherapy directly into the bladder to target the transitional cell carcinoma. This approach also has applications for treating human bladder cancer.

Comfort measures

Making a dog with bladder cancer comfortable is important too. Since these dogs are prone to UTIs, the dog parent should monitor for worsening of urinary signs or other indications of infection. Treating infection with antibiotics can help the dog feel better.

If the bladder cancer has progressed to the point it is obstructing the urethra, some dogs may be a candidate for laser ablation of the mass or balloon dilation to temporarily improve the obstruction. Placing a urethral stent can also help if the tumor is obstructing a ureter and keeping urine from reaching the bladder.

What is the prognosis for bladder cancer?

As you can imagine, the outlook for dogs with bladder cancer varies depending on the type of tumor present, the location, and if the tumor has spread. Unfortunately, without treatment, most dogs with bladder cancer are euthanized within two to four months of diagnosis due to the progression of lower urinary tract signs.

In cases of transitional cell carcinoma, the median survival time (i.e. the length of time after which 50% of affected dogs are still alive) with Piroxicam, or other NSAIDs, is four to six months. With the combination of NSAIDs and chemotherapy, the median survival time is nine to twelve months.

How does bladder cancer progress?

Because transitional cell carcinomas are usually located at the neck of the bladder, urinary obstructions are common as the tumor progresses to the final stages. The tumor may block a ureter so urine from the kidney cannot enter the bladder. Or the tumor may block the urethra so that the patient cannot urinate.

A urinary obstruction can quickly become a life-threatening emergency. If at any point, you think your dog cannot urinate, please make an emergency vet visit immediately.

In other cases, the tumor causes so much inflammation and irritation that it affects the patient’s quality of life. Sadly, I euthanized one of my canine patients a few months after diagnosis because she felt like she had to urinate every twenty minutes. She was so uncomfortable that she wasn’t able to sleep.

Some patients may also become sick because of metastatic spread of disease to other parts of the body. TCC can metastasize to lymph nodes, the lungs, bone, and prostate. In the final stages of metastatic bladder cancer, you may see pain, breathing problems, or swelling of limbs due to blockage of the lymphatic vessels.

Back to my Scottish Terrier patient

Due to the tumor’s location near the ureters and urethra, surgery was not an option for Sally. Her family did not want to pursue chemotherapy but were hoping to keep her comfortable as long as possible. We started her on a daily dose of Piroxicam. While on Piroxicam, we checked her blood work every two months to make sure the medication was not damaging her kidneys. We also checked her urine for secondary infections and treated with antibiotics when needed.

Sally lived another nineteen months after I diagnosed her with a bladder tumor. Unfortunately, her tumor eventually grew into a blood vessel, causing blood loss. Her family knew it was time to consider preparing for dog euthanasia when the bleeding became severe enough that she was anemic and weak. While they were sad to lose their beloved dog, they were also so thankful for the time they had with her after her diagnosis.

Pearls of wisdom about bladder tumors in dogs

I know it can get overwhelming when you and your sweet dog are facing a scary diagnosis like bladder cancer. So let me leave you with a few parting pieces of advice from my years as a veterinarian:

• You know your dog. If your vet is treating your dog for a UTI and it doesn’t seem like your dog is getting better as fast as expected, reach out to your veterinarian. Let him or her know what you are seeing. Be willing to do more diagnostics to get to the bottom of the issue.
• If your veterinarian suspects a bladder tumor, ask about a CADET BRAF test. It is probably the least stressful way to diagnose a TCC and will find 85% of tumors (or 95% if you do the CADET BRAF-PLUS too).
• Although treatment for transitional cell carcinoma is rarely curative, medications such as Piroxicam and/or chemotherapy can help your dog have a good quality of life for many more months.
• Stay in close contact with your vet during the treatment period. Ensure you keep him or her informed of any changes with your dog.
• If you have a high-risk breed of dog such as a Scottie, ask your vet if it would be wise to run the CADET BRAF test as a screening tool every four to six months. Early detection of a TCC allows you to start treatment sooner.

Finally, don’t lose hope. I know that no one wants to hear the word “cancer” in reference to their sweet dog. You can’t change the fact that your dog has bladder cancer. But you can try to enjoy every remaining day together to the fullest.

Has your dog been diagnosed with bladder cancer?

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