The Veterinary Cancer Society held a special meeting last February in Bodega Bay, Calif., to review the mechanisms and discuss treatment of feline sarcomas. I was asked to present our data for the group. My ongoing research into soft tissue sarcoma management was put to the test with the emergence of vaccine-associated sarcomas (VAS) in cats in the early 1990s. We decided to combine our evolving intraoperative radiation therapy program with our intralesional chemotherapy program.

Work done by Dr. Barbara Kitchell and Dr. Alain Theon at UC Davis found that intralesional chemotherapy implants were helpful in controlling tumors. Intraoperative radiation has been shown effective in selected settings to prevent local tumor recurrence.

Using these two powerful tools in the operative site made sense to me since the recurrence rate after surgery alone for VAS was much more than 90 percent. We followed 13 consecutive cases and the data showed only a 33 percent recurrence rate at 100 weeks, whereas others are reporting a 50 percent recurrence by one year.

When we applied a statistical survival test to these cases, we found that cats treated with intraoperative techniques were 8.25 times more likely to survive. This data is exciting when one reviews the difficulty veterinarians have had in controlling the fate of affected cats that develop this often recurrent and fatal cancer.

If my own cat developed VAS and gene therapy was not yet available, I would want a deep, wide radical excision of the mass with skillfully placed chemotherapy implants covering the entire tumor bed. We use a carboplatin and safflower oil colloidal suspension. Then I would set up the open surgical wound for intraoperative radiation therapy using a dose of 1,200 centiGrey (cGy) or Rads. I would want the gentle, expert handling of my cat by good technicians while it undergoes megadose radiation into the tumor bed while under anesthesia. I would trust the careful return trip to the OR to be made quickly for careful wound resterilization and the tedious, meticulous wound closure that leaves no dead space between tissues and therefore no drains.

I would commit to 10 follow-up radiation treatments for my cat to bring the total dose to the tumor bed to over 5,400 cGy. I would also sign up for at least three to six treatments of chemotherapy using adriamycin or preferably carboplatin IV every three to four weeks or more. This multi-modality treatment is the most aggressive protocol on the planet at this time. I would want my own cat and any of my affected patients to get the best option at the onset, because this nasty disease kills cats with unruly, stubborn, relentless, fungating, infiltrating recurrences.

My goal is to encourage colleagues to reach out and challenge cancer. Veterinarians all over the world can guide the outcome of cases with good decision making early in the disease. We are duty- bound to help achieve a cure, especially when it comes to these vaccine-associated, iatrogenic tumors that have emerged as a result of our global preventative vaccination programs for our feline patients.

Dr. Villalobos is medical director of VCA Coast Animal Hospital and Cancer Center in Hermosa Beach and Woodland Hills, Calif., and the 1999 Bustad Companion Animal Veterinarian of the Year.