During our video chats about canine bone cancer with Dr. Johnny Chretin, head of oncology at VCA Animal Hospital West Los Angeles Oncology Center, we asked him some questions that Tripawds members often ask, such as:

“Can Removal of the Primary Tumor Expedite Metastasis in Dogs with Osteosarcoma?”

Dr. Chretin states that in a small pilot study at a veterinary teaching hospital (likely Colorado State University), researchers studied a small group of 15 or 20 dogs who didn’t undergo amputation after being diagnosed with bone cancer because their owners didn’t want the surgery or couldn’t afford it.

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The pilot study followed these dogs throughout the remainder of their lives and concluded that there was no difference in the rate of metastasis among dogs who had amputation surgery versus those dogs who did not. This has also been the case in Dr. Chretin’s practice at VCA Animal Hospital.

Will Radiation Help if Postponing Amputation?

Another study at Colorado State University showed that a large percentage of osteosarcoma dogs who were treated with stereotactic radiation therapy instead of amputation had good long-term survival rates. Instead of succumbing to sudden pathological fractures or untreatable bone cancer, the cancer eventually metastasized as it does for dogs who do undergo amputation.

Why Amputate Sooner Rather than Later?

Although stereotactic radiation therapy is showing great promise for bone cancer dogs, it’s only available at Colorado State University and the University of Florida. For the majority of dogs who cannot undergo this therapy, their pain must be addressed promptly to avoid additional suffering.

“There’s no way to completely get rid of the pain, except taking the leg off,” says Dr. Chretin. “We can do quite a few things that can make them feel pretty darn good, but there’s no way to take all that pain away from them if they have that leg intact. By delaying amputation, the dog is at great risk of a pathological fracture and “that’s as bad as pain gets in animals,” says Dr. Chretin.

Historically, cancer researchers believed that the longer the cancer tumors are left in the body the more time it has to spread. However Dr. Chretin states that this theory is being challenged. Nobody really knows for sure at this point.

“That’s why medicine is really interesting and challenging,” says Dr. Chretin. “Just when we think we understand cancer and say ‘OK this is how it works, this is how the cancer has behaved over the last 20 years,’ all of a sudden someone asks a different question (and everything changes).”

Does the Location of a Tumor Matter?

Finally, we wanted to know, does the location of a dog’s bone cancer tumor determine the severity of the cancer or a prognosis?

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“I’m not aware of anything that says that radius versus humerus is any different,” says Dr. Chretin. Each individual dog’s cancer presents its own unique challenge. For example:

“If anything, having a tumor on a scapula might be better because (your dog) doesn’t necessarily have to lose the leg, you can just lose the scapula. So if you look at things from that perspective, then it’s better to have the tumor higher up.”

When a dog has a leg tumor it can be more challenging to treat, not because the cancer will behave more aggressively but because there is less tissue to work with when attempting to removing the tumor. This is why amputation is often the recommended treatment.

Moving down the leg, clinical studies show that if osteosarcoma is below the wrist, those patients tend to do better and live longer even without chemotherapy. The cancer will still spread but it seems to take longer. Unfortunately, it’s rare for osteosarcoma to present itself in that location.

What about limb sparing for lower extremity tumors?

Limb sparing is often presented as an option for dogs who aren’t amputation candidates or for pawrents who are hesitant about removing the limb. However, the reality is that a limb spare is a lot to put a dog through, plus there is a 30 percent risk of infection and a 30 percent risk of the cancer reoccurring in the same limb. Usually, the limb will have to be amputated anyways.

Stay Tuned for More Canine Cancer Oncology News

This is the latest in a series of video interviews with Dr. Chretin at VCA Animal Hospital West Los Angeles. Stay tuned for additional interview clips with Dr. Chretin that offer informative advice about canine bone cancers, such as:

Tripwds sends sincere thanks to Dr. Chretin and his helpful staff for allowing us to bring this impawtant information to you!

Recommended Reading

North Carolina State University College of Veterinary Medicine: Osteosarcoma in Dogs

PubMed: Palliative radiation therapy for canine osteosarcoma

PDF: Bone Cancer in Greyhounds, Dr. Guillermo Couto, DVM, dip. ACVIM

Dr. Charles Louis Davis, DVM Foundation: Outline of Veterinary Skeletal Pathology

Veterinary Practice News: How to Treat Osteosarcoma When Surgery is Refused

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