When an X-ray reveals the worst possible news—that a pet dog’s limp turns out to be caused by a cancerous tumor—owners have limited options. Amputation and repeated rounds of chemotherapy can extend a pet’s life, but at substantial costs, financial and otherwise. Alternatively, dogs can be given painkilling drugs, but it may only be a few weeks that these medicines keep the canines comfortable.

A recent study by researchers at the School of Veterinary Medicine has shown that another option may be available to pet owners hoping to relieve their dogs’ suffering.

Penn Vet’s Dorothy Cimino Brown and Kimberly Agnello recruited owners of 70 dogs with bone cancer to participate in the study. All of the owners had opted not to pursue amputation and chemotherapy, and were instead interested in simply improving their dogs’ quality of life for the remainder of their lives. 

“There are a lot of owners who will say, ‘I know my dog is terminal, so I’m just going to try to keep him as comfortable as I can for as long as I can,’” Brown says.

Half the dogs received the standard course of painkillers, but the other half received a spinal injection of a compound known as substance-p saporin, or SAP. Though never before tested in pet dogs, earlier research indicated that an injection of this neurotoxin could relieve pain by selectively destroying pain-sensing nerves.

By the study’s design, owners did not know which treatment their dogs received, but were asked to record their pets’ apparent pain levels and activity. When the owners felt that the treatment was no longer effectively relieving their pets’ pain, they were told whether they had been given SAP or the control treatment. At that point, dogs in the “control” group were then offered the spinal injection of SAP.

Brown and Agnello found that SAP was significantly more effective at reducing pain than the traditional painkillers. Owners of nearly three-quarters of dogs receiving the standard drugs asked to be “unblinded” within six weeks, compared to just a quarter of dogs receiving the neurotoxin injection.

“This opens up a whole new realm of treatment possibility,” says Brown. “Usually we would run the medical gamut of pharmaceutical options and then euthanize, but now if we have a neurotoxin that we can offer, we’ve actually increased by another step our potential to improve these animals’ quality of life.”

The results have the potential not only to improve the lives of sick dogs, but humans as well, as dogs have served as a good model for how painkillers might work in people.

“The idea is that hopefully what happens in these dogs is more predictive of what happens in people than what happens in mice,” says Brown. “This is the direct predecessor to a human clinical trial.”