It’s a diagnosis no cat lover wants to consider when they walk into the veterinarian’s office, but sadly, breast cancer does strike our feline friends. In cats the disease is very aggressive, and it typically doesn’t respond well to treatments. Told that the cancer will probably return even after surgery, owners are left deciding whether to put their cat through the trauma of an operation or simply wait to put her down.

The tragic and aggressive nature of breast cancer in cats is why Canadian researchers at the Ontario Veterinary College in Guelph and McMaster University are busy with a new clinical trial they hope will help heal cats while also providing insight into human cancer that cannot be found in studies of lab mice. If the vaccines developed in this trial are successful, they could prove useful in humans, which is why this is the first veterinary clinical trial to receiving funding from the Canadian Breast Cancer Foundation.

While the evolution of this trial could help human patients in the future, right now, the focus is on six house cats who were recruited from veterinarians offices in Ontario. The response from owners was more enthusiastic than anticipated. Many families stepped forward to volunteer their cats, hoping to spare the animals from having to undergo chemotherapy.

“The goal here is to benefit the cats,” says Dr. Brian Lichty of McMaster University’s Immunology Research Centre. “The form of breast cancer that cats get is less variable than what humans get. It really represents the worst case scenario for women.”

Lichty and his colleague, Dr. Paul Woods, professor of internal medicine and oncology at the Ontario Veterinary College, are leading a team in treating cats with two doses of vaccine that kill tumors while boosting the cats’ immune systems. The cats receive the usual standard of care, surgery, between the two doses of vaccine.

The first vaccine is delivered as a routine shot that can be given by the cat’s regular vet, before the surgery. The second dose is administered at Ontario Veterinary College four weeks after the surgery as an intravenous infusion.

The vaccines aren’t meant to replace surgery, but rather make this common treatment for breast cancer more effective.

“Typically what we would suggest would be surgical removal,” says Woods, co-director of the University of Guelph’s Institute for Comparative Cancer Investigation. “But it might come back.”

Even after surgery, the odds for cats with breast cancer aren’t good.

“Historically, 90 percent of them will relapse in a year,” says Litchy.

The high likelihood of seeing the cancer return after surgery is a factor in why many cat lovers choose to forgo treatments. Litchy and Wood hope this new vaccine treatment will eventually be used to complement existing cancer treatments and reduce the relapse rate.

“Just like in people, we’re often looking for better ways to treat pets,” says Woods.

Maci, a 12-year-old house cat, was the first cat to receive both courses of the new treatment.

“She’s doing great,” says Lichty, who adds that Maci is now back at home with her family in Toronto.

According to Woods, Maci’s future is still uncertain, as it’s not yet possible to know whether she’s cured.

“It’s too early to tell. The good news is she handled the treatment quite well,” Woods says.

The clinical trial is expected to continue over the next two years, with the scientists keeping tabs on Maci and the cats that come after her, monitoring the pets for signs of relapse.

“Ideally, we would like to prevent [relapse]. That would be my gold standard,” says Woods.

Even if relapse can’t be prevented, researchers hope to postpone the recurrence for as long as possible so that the cats and their families can enjoy an increased quality of life.

The researchers say the trial is a win-win for cats like Maci, and for scientists. The vaccines have been tested to meet health regulations, and the treatment has been proven safe. The cats get cutting-edge treatment, while the researchers get to observe the vaccine effectiveness in an animal genetically similar to humans.

“It’s a big leap to go from mouse research to human research, and we’ve been missing out,” says Litchy.

Five other cats have started treatment in the trial. The team will have treated nine cats by the end of 2014, and it plans to have 24 cats enrolled before the trial is complete.

While the researchers continue to work on treating this difficult and often fatal disease, many pet cats will avoid breast cancer, thanks to thanks to interventions early in life.

“Having a cat spayed before her first heat almost completely prevents it,” says Lichty.

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About the author: Heather Marcoux is a freelance writer in Alberta, Canada. Her beloved Ghost Cat was once her only animal, but Specter the kitten and GhostBuster the dog make her fur family complete. Heather is also a wife, a bad cook and a former TV journalist. Some of her friends have hidden her feed because of an excess of cat pictures. If you don’t mind cat pictures, you can follow her on Twitter; she also posts pet GIFs on Google +