Veterinarians use medication to treat invasive transitional cell carcinoma (TCC), the most common form of canine cancer of the bladder, to avoid the adverse effects of radiation therapy. Medication therapy for TCC may be administered through either traditional chemotherapy drugs or the use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as piroxicam. NSAIDs cause few side effects--mainly stomach or intestinal irritation--and are much less toxic than chemotherapy drugs.
Bladder Cancer Primer
Bladder cancer, which CanineCancer.com reports is the most common type of canine urinary tract cancer, develops most often as a TCC. TCC, directly related to the highly invasive form of bladder cancer that develops in humans, establishes itself in the form of a malignant tumor deep in the bladder wall--usually in the neck region--and obstructs the flow of urine from the kidneys into the bladder. It is this location that makes surgical removal of the tumor inadvisable. Prognosis is poor, as TCC is aggressive and not usually diagnosed until it reaches an advanced stage.
NSAIDs like piroxicam, referred to as "cox inhibitors" because they block the actions of the cyclooxygenase enzymes COX-1 and COX-2, are used to reduce TCC-related bladder inflammation caused by the prostaglandins that COX-2 produces in the presence of inflammation. Although the connection is not entirely understood, veterinarians are finding that piroxicam may increase tumor cell death and negatively impact the development of the tumor's supportive blood vessels in certain cancers; in layman's terms, veterinarians think piroxicam increases cancer survival times. Piroxicam is not commonly prescribed by veterinarians for pain relief.
Piroxicam is generally manufactured in 10mg and 20mg capsules. Veterinarians dose piroxicam at 0.15mg per pound--or 0.3 mg/kg--of patient weight once a day. Treatment length depends upon patient reaction to the medication, the development of any adverse side effects and the nature of the medical condition. Dog owners must complete the entire treatment plan for it to produce the desired result.
Piroxicam and Chemotherapy
Medical protocols combine piroxicam with chemotherapeutic drugs, such as cisplatin or mitoxantrone, to treat TCC, skin and oral squamous-cell carcinoma, prostatic carcinoma and certain abnormal rectal growths. The average survival time of dogs treated with a combination of piroxicam and cisplatin for oral squamous-cell carcinoma has risen to close to eight months. The average survival time of canine TCC patients treated with piroxicam and mitoxantrone is just under one year, according to author and veterinarian Barbara Forney.
Contraindications and Side Effects
Gastrointestinal irritation and renal toxicity sometimes develop as a result of piroxicam therapy. Forney advises veterinarians to supplement piroxicam with fluids as a matter of course and to definitely not prescribe the drug for dehydrated patients. Patients taking certain medications, such as corticosteroids and diruetics, or those suffering from cardiac problems may also suffer adverse effects from the drug. Dog owners should confer with their veterinarians to determine whether any currently prescribed medications will negatively interact with piroxicam.