Dogs and Cancer: Get the Facts

A vet answers 10 commonly asked questions about cancer in dogs.

By Sandy Eckstein
WebMD Pet Health Feature

Reviewed by Audrey Cook, BVM&S

Cancer is the leading cause of death in dogs over the age of 10. But half of all cancers are curable if caught early, experts say. WebMD talked to Dave Ruslander, a veterinary oncologist and past president of the Veterinary Cancer Society, about canine cancers and the latest treatments for dogs diagnosed with the disease.

Q: How common is cancer in dogs, and what are some of the common cancers found in dogs?

A: It has gotten to be pretty common, especially in older dogs. Fifty percent of dogs over the age of 10 develop cancer at some point. We see malignant lymphoma, which is a tumor of the lymph nodes. We see mast cell tumors, which is a form of skin cancer. There are mammary gland tumors, or breast cancer, and soft tissue sarcomas. We also see a fair amount of bone cancer in dogs.

Q: What are some of the symptoms of cancer in dogs?

A: The warning signs of cancer in dogs are very similar to that in people. A lump or a bump, a wound that doesn't heal, any kind of swelling, enlarged lymph nodes, a lameness or swelling in the bone, abnormal bleeding. Those are all classic signs. But sometimes there are little or no signs, at least early on. So any time an animal isn't feeling well, or there's something abnormal or not quite right, the owner needs to bring it to the attention of their veterinarian.

Q: What's causing these high cancer rates in our dogs?

A: I think people are taking better and better care of their animals and pets are living longer and longer, so we're seeing more animals live to an age where they develop cancer.

Years past, many dogs died from common illnesses or were hit by a car. But now we have vaccines and we keep our dogs indoors, so they're just around longer.

There also seems to be a genetic component in some cancers, because we've seen where some breeds seem more prone to cancers than others.

Q: So some breeds are more prone to cancers? Are mixed-breed dogs less likely to get cancer?

A: Any time you have an inbred population, you don't know what else is being inherited along with the traits you want. People like golden retrievers because they look like golden retrievers. But what else is being passed through that line? Golden retrievers have a strong incidence of cancer. So do boxers, flat-coated retrievers, Bernese Mountain dogs. All of those breeds, and others, have specific cancers that we see. That's showing that there are probably specific genetic components to some cancers. But it's still a question of how much is genetics versus environmental factors.

Because mixed-breed dogs come from a much larger gene pool, they would be less likely to get genetic-based cancers. But that doesn't do anything for spontaneous cancers or environmentally caused cancers.

Q: What can I do to help prevent my dog from getting cancer?

A: The biggest thing is spaying your dog. If you spay a dog before its first heat you'll reduce the chance of mammary cancer eight-fold, just because of the hormonal influence.

Good oral care can help decrease oral cancers. And if you're buying a purebred dog, check its line to see if there's a specific kind of cancer in that breed's line.

But overall, prevention is difficult because we don't know the causes of most cancers. I think, rather than trying to prevent cancer, identifying it early and treating it quickly is the better strategy.

Q: If my dog has cancer, does that mean he's going to die?

A: Absolutely not. Probably the majority of the cancers we see can be dealt with surgically. A lot of the breast cancers, a lot of the mast cell tumors, a lot of skin tumors, soft tissue sarcomas, many of those tumors can be removed surgically and are cured. Even in situations where they have advanced to a lymph node, there are options that can prolong your dog's life and even cure him.

Q: What kinds of treatments are available for dogs with cancer?

A: We have pretty much all the options that are available to people. There's surgery, obviously. Radiation therapy is available in about 40 facilities around the country. Chemotherapy has become commonplace. Now some places are even doing research and clinical treatment of patients with immunotherapy tumor vaccines, where we're using the immune system to stimulate the destruction of the cancer.

Q: The FDA approved the first drug for treating canine cancer in dogs in June 2009. What other advancements will we be seeing in the treatment of canine cancers?

A: There have been several things, like the tumor vaccine I just mentioned. There is a new vaccine against oral melanomas, the most common oral tumor. Radiation therapy and technology is expanding so that the machines that we're using can now treat brain tumors and nasal tumors and deep-seated tumors that previously we couldn't access surgically.

Veterinary oncology has progressed amazingly in the past two decades. Twenty years ago, most people didn't even know dogs got cancer. Today it's common to find people whose dogs have been treated for cancer. There are so many more facilities for treating canine cancer now, and there are veterinarians who do nothing but treat cancer.

Q: What does it cost to treat a dog with cancer?

A: It varies. There's the diagnostic testing that's needed prior to doing any kind of therapy, and that can range from $200 to $1,000. Then treating the cancer can range from a simple surgery for $1,000 all the way up to $15,000 if we're dealing with something complicated that also needs radiation therapy and chemotherapy along with the surgery. They're even doing bone marrow transplants for dogs with lymphoma. That can be very expensive.

(Note: These are costs for top-level treatment at a specialist hospital. Prices for less involved options at a general veterinary practice may be much less. Costs may also vary a lot depending on where you live.)

Q: What's the cure rate for dogs with cancer?

A: Overall, for all malignancies that we see, it's probably in the 60-plus percent range. There are a lot of patients out there with just lumps and bumps that are being taken off by their regular veterinarian and they have a very good long-term prognosis.

Now if the cancers are left untreated, we're talking survival times in the months, not years.