Vaccine -Associated Sarcomas

In our attempt to keep our cats healthy, are we actually hurting them?

Article by Cheryl S. Smith (Contributor for Catnip)

Excerpts include comments by:

Dr. Jean Dodds, DVM, President of HemoPet

Tony More, BVSc, MVSc, Associate Professor at Tufts University School of Veterinary Medicine

Treatment Options:

As with most tumors, surgery is the first response. Dodds points out that one of the reasons for giving vaccinations in the limbs and off the middle of the cat is so that potential tumors can be removed more effectively. "You take as much tissue as you can around it, but many still come back anyway", she says. Moore explains that veterinary surgeons would like to take the margins of normal tissue around the tumor that are at least two to three inches from the tumor edge in all directions, and that's a lot of tissue on a cat.

Because this ideal excision usually is not possible, radiation therapy and / or chemotherapy are often used to try to kill any cancer cells left at the edges of the surgery.

"The problem has been that radiation continues to travel through tissue", Moore notes. "Where vaccines have traditionally been given, there are sensitive organs underneath, such as the lungs or the stomach and kidneys".

The new vaccination protocols will allow more effective use of radiation, and the technology itself has improved.

"With electron-beam radiation, we can regulate how deep the beam penetrates, so we can give a higher dose and better kill the dividing cells. We also have computer-assisted planning, so we can work out where the beams can go," Moore adds.

Radiation therapy for veterinary patients is relatively new, and Moore estimates that is is available in maybe 20 private practices and veterinary teaching hospitals across the country. There is currently a four-week wait for radiation therapy at Tufts University. But just 10 years ago there were probably only three machines in the entire country to which veterinarians had access, so the situation is improving.

The "Quality of Life"

Treatment is intense. Surgery is followed by a month of radiation, given five days each week. This is followed by three months of chemotherapy, most often with doxorubicin or carboplatin. Moore points out that "it's really hard to cure animals of cancer because of the quality-of-life issues". Humans are treated very aggressively and get very ill, but if they're cured they'll have many more years of good living ahead.

"To get animals that sick," Moore notes, "you can't explain to them, you can't support them really well through the therapy, and if you do get a cure, how much have you given them?"

Still, Moore is seeing cats that previously would have died four to six months post-surgery but now live up to 18 months before the tumor recurs, or they have no recurrence at all. That's the good news.

The bad news is that oncologists are now seeing tumors metastasize (spread into other body systems). Some theorize that vaccine-associated sarcomas are different and more aggressive, but others think that because cats are surviving longer they're able to see things previously undetectable.

Ongoing Research

Further research is underway for even better solutions. The University of Wisconsin is examining new formulations of doxorubicin for more effective chemotherapy.

The Animal Medical Center in New York City is looking at increasing the oxygenation of cancer cells (which makes them easier to kill) by transfusing a hemoglobin substance. And the University of Colorado is investigating the actual genome of cat sarcomas compared with normal cat chromosomes.

No one knows what the next big advance will be, but the outlook has already improved and will undoubtedly brighten further as the cause and effective treatment of feline vaccine-associated sarcomas is more completely investigated and understood.

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