Lewis, an eight-year-old Golden Retriever, qualified for the prestigious 2013 Master National hunt test in Kansas. As part of his final preparation, Lewis ran the first series of a master hunt test before the competition as a confidence builder. He nailed it.
But later that day, when jumping to catch a tennis ball, Lewis let out a yelp. His owner, Paige Jones, noticed that he was limping and holding his right front leg out to the side.
Lewis had injured his wrist twice before, so Jones assumed he had aggravated the old soft-tissue injury. She scratched him from the Master test and brought him to the vet a few days later. By then, Lewis was no longer limping, so Jones was not overly concerned. Unfortunately, the news she was about to receive from the veterinarian was cause for concern.
Lewis was diagnosed with osteosarcoma, an aggressive form of bone cancer, in his right ulna near the wrist.
“It was the last thing I expected,” Jones said.
Jones’ surgical options were to either amputate Lewis’ entire right leg and then follow up with chemotherapy, or undergo limb-sparing surgical excision of the diseased portion of the ulna bone and follow up with chemotherapy.
This was not the first time Jones was faced with a tough decision. Her Golden Retriever, Dewey, had been diagnosed with axial osteosarcoma in 2005.
“When making decisions about Dewey, my husband and I resolved to do all we could to prolong a quality life without sustaining or inflicting more suffering on the dog,” she said. “Having this framework in place made the decision easier in Lewis’ case.”
Even though the recovery time would be shorter with amputation, Jones opted for the limb-sparing surgery. “We believed that saving Lewis’ limb was the right choice,” she said. “We had faith that he could beat the odds since the tumor was in the ulna and seemed to have well-defined margins.”
She was right. Lewis recovered well from surgery and the tumor was removed with good margins.
Since the surgery was only palliative, Jones needed to work out the details of the chemotherapy. While researching options for specialists and treatments, she learned about a clinical trial at Penn Vet led by Dr. Nicola Mason, Assistant Professor of Medicine & Pathobiology. This boundary-pushing trial aims to prevent metastasis of cancer and prolong overall survival in dogs with osteosarcoma.
Knowing that Lewis’ treatment only offered a median survival of 200-300 days, Jones decided to apply for the trial.
The Power of Immunotherapy
Mason has studied cancer and immunotherapy for more than 15 years. Her groundbreaking work harnesses the power of the immune system to specifically target and kill malignant cells and provide long-term immunological memory against cancer antigens to prevent tumor recurrence.
In this trial, Mason administers a vaccine created by Advaxis, Inc. that uses a non-disease-causing form of the listeria bacteria, modified to express a protein found in cancer cells.
“The goal of the vaccine is to trigger an immune response to that protein,” Mason said. “The vaccine educates the immune system to recognize tumor cells and to kill them.”
To Jones’ relief, Lewis was accepted in the study. Always one to stand out in a crowd, Lewis is unique among the other dogs in this particular trial. “He’s the only dog in the study with four legs,” Mason said. “The other dogs have all undergone limb amputation.”
Since Lewis’ tumor was surgically removed like the other dogs, he still qualified for the trial. (Mason also has enrolled dogs with osteosarcoma that cannot undergo amputation for a separate study evaluating whether the vaccine can be used to treat the primary tumor as well as prevent spread of the disease, in combination with radiation therapy.)
Lewis received his first vaccination in January 2014. The series of four vaccines – three in an initial series, plus a booster – was completed in November 2014. “He sailed through his vaccines without any problems,” Mason said.
Lewis now makes the trip from Alexandria, VA, to see Dr. Mason every two months for check ups. During a recent March visit, Mason took radiographs of Lewis’ chest, performed a full clinical and cardiac assessment, and analyzed his blood work.
“Everything was normal,” Mason said. “There was no evidence of metastatic disease in his chest.”
Lewis has now surpassed the 500-day milestone, having survived free of metastatic disease since his September 2013 diagnosis of osteosarcoma.
According to Mason, two other dogs in the trial are about to hit the three-year mark. “These are times that are unheard of,” she said. “To have two out of 18 dogs reach their three-year milestone, and to have a bunch of others, like Lewis, coming up behind them is exciting.”
One in a Million
Lewis has taken everything in stride. “That’s the thing about dogs,” Jones said. “He doesn’t know anything is different. It’s like he never had cancer at all.”
“Lewis is a fabulous dog,” Mason added. “He has a perfect personality.”
The energetic Golden Retriever qualified for the 2014 Master Nationals in California in October. Due to the long distance he would have to travel, Lewis did not participate. He has since retired, although he still trains from time to time. He’ll be 10 years old in June.
Jones’ gratitude toward Mason is apparent. “You can tell she really cares for the animals,” Jones said. “She’s one in a million.”
In addition to caring deeply for her animal patients, Mason is excited about the potential benefits her trial offers human patients, as well.
“If you look at a bone tumor from a dog and a bone tumor from a child, you cannot tell which is which,” Mason said.
Data from Mason’s canine trials could pave the way for similar treatments for human cancer patients.
Aratana Therapeutics has submitted information to the USDA, which is evaluating the vaccine for use in dogs. The next step will be to get a conditional license so that the vaccine will be more widely available.
In addition, Phase I trials using the vaccine will soon begin in people with breast, esophageal, and gastric cancer, as well as osteosarcoma. A pediatric osteosarcoma trial also will be underway in the near future.
“It’s really a gift to be able to help dogs and, in turn, help people,” Mason said.
One of the greatest gifts is also being able to provide hope to owners like Jones who are so devoted to their dogs.
“We weren’t ready to let Lewis go,” Jones said, fighting back tears. “We wanted to give him any sort of chance possible. Now we get him for a long time.”
Learn more about Dr. Mason’s canine cancer studies.