MAN'S BEST FRIENDS
Treating cancer in cats and dogs advances human
The other day Katie, a golden retriever who lives on five acres in El Dorado County, took a leisurely
walk out to the barn, sniffed around and had a nap. Not remarkable for a dog, except that nobody expected
this one to be alive today.
Katie's story may involve 21st century advances in molecular biology and genomics, but the basic plot
is an ancient one: Man takes care of dog; dog repays man many times over.
Katie was among 57 dogs, all with end-stage cancers, to receive an experimental drug through a clinical
trial at the UC Davis Small Animal Hospital. The dogs, who had exhausted all conventional therapies, each
gained extra time more than two years so far in Katie's case. In return, the dogs gave medical science
some of the first evidence that molecules known as multi-targeted kinase inhibitors, taken in tablet form,
are safe and effective against a variety of naturally occurring cancers.
More than half of all dogs and cats that live past age 10 will develop cancer. Thousands come to the
UC Davis Small Animal Hospital every year for treatment, passing this mural in the lobby.
UC Davis Cancer Center is at the forefront
of efforts to coordinate animal and human cancer research to improve cancer treatment for people as well
as pets. The Cancer Center's Integrated
Cancer Research Program, a collaboration of more than 200 investigators from more than a dozen scientific
disciplines, includes 19 veterinary oncologists and basic scientists at the UC
Davis School of Veterinary Medicine.
"Everyone wins in this collaboration," says Cheryl London, an assistant professor of surgical
and radiological sciences in the School of Veterinary Medicine. A Harvard-trained veterinary oncologist,
London heads the UC Davis Cancer Center's
Cancer Biology in Animals Program together with Ron Wisdom, assistant professor of hematology/oncology.
"Our dog and cat patients win, because they get access to novel therapeutics that can potentially
help slow down their cancer progression or even cure their cancers," London says. "And we win,
because we learn more about the potential efficacy of these drugs for treating human cancers."
Cheryl London, foreground, views Basil's chest films. Once filled with cancer, the dog's lungs have
been clear for two years, thanks to an experimental drug.
Clinical trials of new anti-cancer drugs can be conducted more quickly in dogs and cats, because the
regulatory oversight that applies to human test subjects doesn't exist for animals. Trials in pets are
also less expensive, because charges for everything from blood tests to CT scans are lower in veterinary
medicine. A cancer clinical trial that might take five years and many millions of dollars in human volunteers
can be completed in five months for $100,000 in animals.
Katie's remission after taking SU11654, an experimental oral anti-cancer agent, gave oncologists important
information about a promising new agent long before it could have been obtained through human clinical
One of London's newest clinical trials will test another investigational anti-cancer drug, 2-methoxyestradiol.
The drug 2-ME2 for short is being studied in human clinical trials involving patients with
prostate cancer, metastatic breast cancer and multiple myeloma, a malignancy of certain white blood cells.
London hopes the drug may also work against sarcoma, a soft-tissue cancer that is very common in cats
and dogs. She has already shown that the drug kills sarcoma cells in the laboratory dish. Now she hopes
to find that the drug does the same for sarcoma tumors in pets. She received funding for her study, however,
from a foundation dedicated to finding cures for human cancers.
The V Foundation, a North Carolina-based organization established in memory of ESPN broadcaster Jim Valvano,
recognized that an animal study might generate important answers for human sarcoma patients and do so
While sarcomas are common in dogs and cats, they are relatively uncommon in humans, affecting about 8,100
children and adults in the United States each year. The larger pool of potential animal sarcoma patients
makes a clinical trial easier to organize in cats and dogs than in people.
London expects to know sometime this year whether 2-ME2 is effective against canine and feline sarcomas.
If it is, veterinary oncologists will have a new tool for fighting a common cancer in pets and a path
will be cleared for tests in humans with sarcomas.
Dogs like this yellow lab develop many of the same cancers as humans and respond to the same treatments.
Cancer wasn't Katie's first crisis. The golden retriever was picked up as a stray, with a litter of puppies,
about six years ago. Mother and pups were taken to an animal shelter, the pups were adopted and Katie
was sent to Homeward Bound, a golden retriever rescue organization based in Elverta. Two families, in
quick succession, adopted Katie. But the dog tried to run away from both adoptive homes, winding up back
at the rescue organization each time.
The third adoption took. Carla and Michael McCreary tracked Katie down and brought her back home whenever
she ran away. At some point, the dog stopped trying to escape. At obedience school with Carla, Katie got
off to a rough start but went on to earn effusive praise from the instructor at graduation. As a volunteer
with the Sacramento SPCA's Love on Loan pet visitation program, Katie revealed a special empathy for the
most withdrawn kids at the Children's Receiving Home, a Sacramento shelter for abused and abandoned children
and adolescents. "Katie," Carla says, "gives back everything she is given."
Cancer claimed Basil's hind leg and spread throughout his body, but a clinical trial at UC Davis put
the disease into remission.
Two years ago, Carla found a lump on the dog's chest. She and her husband went to extraordinary lengths
for their adopted pooch: two surgeries, chemotherapy and, when those measures failed, participation in
London's clinical trial. The trial required daily medication at home and monthly trips to UC
Davis for blood work and X-rays. And London couldn't promise the effort would make any difference
in Katie's illness.
Of the 57 dogs with advanced malignancy enrolled in the trial of SU11654, 16 experienced no progression
of disease during the study and 11 had measurable reductions in tumor burden. Six dogs, including Katie
and Basil (shown on this issue's cover), had a complete response. Their tumors
Katie, now 8 or 9 years old, returns to see London every three months. The dog's chest X-rays remain
clear and her blood work is perfect.