Dear OncoLink "Ask the Experts,"
Our 5 and a half-year-old male Cocker Spaniel was recently diagnosed with transitional cell carcinoma of the bladder. The tumor is located in an area where surgical removal is a possibility, but not recommended. My wife and I have opted to begin treatment for him by administering Cytosec daily, along with another medication to help deter any GI distress. What are the usual side effects with the use of this medication? We feel so helpless now and we want to everything within our means to help our boy.
Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:
Transitional cell carcinoma is the most common type of bladder cancer in dogs. While these tumors can appear as solitary discrete masses on diagnostic tests such as X-rays and sonograms, there is often undetectable microscopic extension well beyond the apparent tumor mass. This is why surgery is not strongly encouraged for these tumors. Conventional chemotherapy regimens have a very modest palliative effect on these tumors. Recently, a nonsteroidal anti-inflammatory drug (NSAID) called piroxicam (trade name Feldene) has been shown to have some anti-tumor activity against several canine cancers, including transitional cell carcinoma. Therefore, piroxicam has two potentially beneficial effects. First, it is very effective when combined with the appropriate antibiotics in decreasing inflammation associated with infections. This alone can greatly improve symptoms, and is often effective within 1-2 days. In addition, it is helpful in relieving pain associated with tumor-induced inflammation.
As a separate mechanism, piroxicam can also have anti-tumor activity. This anti-tumor effect may take weeks to months to become manifest. So, as long as the dog is tolerating the piroxicam well, and the symptoms associated with the tumor seem to be improved, then it is worth maintaining the dog on piroxicam even if the tumor does not decrease in size right away.
Piroxicam, similar to other NSAIDs such as aspirin and ibuprofen, can cause gastrointestinal irritation and ulceration. Therefore, anti-ulcer medications such as misoprostol (trade name Cytotec) are often prescribed prophylactically to try and avoid NSAID side effects. NSAIDs should be given with a meal, and dogs receiving these drugs should be monitored closely for signs of GI upset, such as loss of appetite, depression, vomiting (especially if of a coffee grounds appearance), and black tar-like stools. If any of these symptoms occur, stop the NSAID, continue with any prescribed anti-ulcer medications, and call your veterinarian immediately.