What is bladder cancer?
Bladder cancers usually arise from the surface of the bladder (carcinomas). They can be very superficial and localised when they start developing, but they are often diagnosed late when they have already infiltered the deeper tissues of the bladder wall, and have become broad and ill-defined tissue proliferation on the surface. Over time, they can spread to the regional lymph nodes and more distant organs such as the lungs, but metastases rarely become a clinical problem unlike the bladder infiltration. Bladder cancer may also infiltrate into the urethra (tube connecting the bladder to the outside), which may result in complete obstruction and preventing any urination (emergency). It may also obstruct the ureters (tubes connecting the kidneys to the bladder), and preventing the urine produces by the kidneys to go to the bladder.
Occasionally, we may see other types of bladder cancers such as tumours of the muscles (sarcoma) or the lymphocytes (lymphoma). Some inflammatory lesions may also take the appearance of a bladder cancer, but this remains infrequent.
How can I tell if my pet has bladder cancer?
Most dogs with a bladder cancer will be presented because of changes in their urination habit. This could be because of blood-tinged urine, increased frequency of the urination, straining whilst urinating, and sometimes even having some accidents in the house.
What is the cause of bladder cancer?
The origin of bladder cancer is multifactorial. There is a strong breed predisposition to bladder cancer in dogs. Predisposed breeds include Scottish terrier, Shetland sheepdog, beagle and West Highland white terrier. About 70-80% of canine bladder cancers also carry a specific mutation (BRAF V595E).
Some risk factors also include exposure to chemicals (herbicides/insecticides), obesity and there may be a hormonal influence as females are overrepresented.
How is bladder cancer diagnosed?
An abdominal ultrasound is usually performed initially, and allows the detection of a possible bladder mass. A few cells can be collected for further analysis (cytology), or directly in the urine or by placing a catheter within the bladder. This may not be sufficient to confirm the diagnosis, which may require taking biopsies by cystoscopy (camera and forceps into the bladder). Over the last few years, the use of a genetic test to detect the BRAF V595E mutation has become widely available. This test can be performed on urine or on small samples from the tumour, and can confirm the diagnosis of a cancer if it is positive, but about 20-30% cases of cancer may still be negative.
How is bladder cancer treated?
When a bladder cancer is still very localised, it may be possible to surgically excise it and to follow the excision with maintenance of oral drugs. The benefit of surgical excision remains controversial as the cancer will recur in many cases, but some dogs will enjoy long term remissions.
In most cases, the cancer is too extensive to be excised. In those cases, the gold standard treatment is a course of non-steroidal anti-inflammatories and chemotherapy. Different types of anti-inflammatories and chemotherapy drugs can be prescribed sequentially over time when the cancer progresses.
Our Interventional team may also be able to propose more localised treatments. Chemotherapy can also be administered directly into the blood supply of the tumour (intra-arterial chemotherapy) to increase the concentration of the drug. Laser ablation of the bladder mass can also be performed to debulk it. The potential impact of these therapies on the long-term outcome remains unclear.
In case of obstruction of the urethra or ureters, our Interventional can also offer urethral stenting, ureteral stenting or subcutaneous ureteral bypass.
Our medical oncology team may also be able to offer other medical options, as we are always looking into innovative therapies. Multiple treatment options are possible and can be discussed for each individual case with our oncology team.
What is the prognosis of bladder cancer?
Published median survival times of dogs with bladder cancer managed with anti-inflammatories and chemotherapy vary between 5-11 months. The prognosis can be very variable, however, and depends on the localisation and stage of the cancer. The treatment(s) prescribed will also influence the outcome and it is not uncommon in our experience for dogs to leave > 1 year with good quality of life, when different treatments are prescribed.