Vaccine Associated Sarcomas in Cats (VAS)

Dr. Gail Mason, DVM, MA, DACVIM
Kathi Smith, RVT, Internal Medicine & Oncology Technician

Vaccinating domestic cats against serious infectious disease is an important step in good quality health care. The diseases that are vaccinated for can cause serious illness and/or death. Vaccination against rabies is an important pet health, public health, and legal issue as well. However, due to statistical association between some vaccines and subsequent sarcoma development which was noted over the last decade, vaccine types and protocols are under heavy scrutiny.

Injection site sarcomas, as the name implies, can develop in areas of the body where vaccination has taken place. This typically is between the animal's shoulder blades (interscapular) or on a hind limb. These tumors are aggressive in nature and are associated with significant tissue inflammation and decay. They tend to infiltrate the normal tissues with malignant tendrils making surgical excision difficult. Although they are considered to be in the class of "soft tissue sarcomas," they have a higher metastatic rate than other tumors of this class.

Current recommendations suggest that masses noted at vaccine sites which are present 3 or more months post-vaccinations, are greater than 2cm or are rapidly growing should be dealt with in a timely fashion. An incisional biopsy can confirm a VAS. Matastasis can occur to local lymph nodes and to the lungs.

Staging of the patient to evaluate the extent of the disease may include: 
• Chest radiographs (x-rays) 
• Abdominal radiographs
• Routine blood screening
• Ultrasonography or a CT scan

Patients have longer survival times when an aggressive, initial resection is performed and is followed by radiation therapy. If the tumor is located on a limb, it may be necessary to perform a limb amputation. As unpleasant as this idea is, it is well-documented that patient recovery is rapid and quality of life can be excellent. Chemotherapy has also been used in the treatment of VAS but its exact efficiency remains to be determined. Most published veterinary medical reports have described use of either doxorubicin and/or carboplatin.

Unfortunately, cats with VAS may have a guarded to poor long term prognosis. Remission times are variable, but most often reported as being between 8 months to 1.6 years. Initial aggressive and complete resection appear to positively influence outcomes and longer, excellent quality remissions have been documented.

Transitional Cell Sarcomas in Dogs

Dr. Gail Mason, DVM, MA, DACVIM
Kathi Smith, RVT, Internal Medicine & Oncology Technician

Primary cancer of the bladder in dogs is relatively uncommon. Of those occurring in that location, transitional cell carcinoma (TCC) accounts for 50-80% of all reported cases.

Diagnosis of Transitional Cell Carcinomas
The clinical signs of bladder cancer in dogs are generally similar to those of urinary tract infections (cystitis) and urinary stones (cystic calculi). For this reason diagnosis by cytology of biopsy is required. Tests used in diagnosing TCC include:

• Urinalysis
• Cytology (urine or tissue aspirate)
• ultrasonography (+/- guided needle biopsy)
• abdominal radiographs (x-rays)
• routine bloodwork
• cystoscopy (fiberoptic exam of bladder/urethra)

Treatment for TCC
The overall metastatic rate for TCC is approximately 50%, and unfortunately, at this time there is no know cure of this disease. Control of local disease and its clinical signs are the main goal of therapy.

Surgery for TCC
Surgery can be a viable option for TCC patients but often the extent and tumor location provide multiple challenges. Surgery is generally considered palliative (vs. curative) for this tumor and may include:
• partial bladder removal (cystectomy)
• urinary tract diversion (catheter placement)
• bladder reconstruction

The risks and benefits expected with surgical treatment of TCC are worthy of a detailed discussion with a veterinary surgical specialist to determine if it is a reasonable option for a particular patient.

Chemotherapy for TCC
Systemic chemotherapy for bladder or urethral TCC has produced varying results. Drugs that have been employed include:
• Doxorubicin
• Mitoxantrone
• Cisplatin
• Cyclophosphamide

Though these drugs are relatively well tolerated in animals, most all reported survival times of less than one year. A recent retrospect study of 25 dogs with inoperable urinary bladder carcinoma suggested a survival advantage might exist when dogs receive doxorubicin (or mitoxantrone) in addition to a platinum-based compound (cisplatin or carboplatin). Similar combinations warrant further investigation. The drugs do, however, frequently abate the patientÕs symptoms.

Interestingly, though not anticancer drugs per se, piroxicam and other non-steroidal anti-inflammatory drugs (deracoxib, metacam) have shown activity against TCC in dogs. They can be used alone or in combination with chemotherapeutic agents.

Anti-inflammatory drugs can exert antitumor activity by several mechanisms. They appear to include reduction of swelling, pain, formation of new blood vessels in tumor tissue, and perhaps direct antitumor effects on malignant cells.

Piroxicam can be extremely useful in the management of TCC in dogs. It works rapidly to reduce tumor swelling and obstruction to urine outflow. As a single agent, it is known to control TCC for at least as long as multiple-drug protocols.

These drugs can be used safely in many dogs and cats. However, adverse reactions in the gastrointestinal tract (gastritis, vomiting, bleeding ulcers) and in renal (kidney) function have been reported. If your pet is taking such a drug, monitor him/her for signs of decreased appetite, vomiting, or dark black stools, which may necessitate drug withdrawal.

Early diagnosis and intervention in patients with TCC are likely to produce the most favorable prognosis. Currently, recommended combination therapy with surgery, anti-inflammatory agents, and chemotherapeutics offer the best chance of tumor control. The long-term prognosis still remains guarded to poor as remission times uncommonly exceed 1 year. However, remission time can be good quality time for both pet and owner.