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Does Radon Cause Cancer in Pets?

A few years ago, I saw two dogs from the same household presenting to the emergency room for similar signs: one, a geriatric Golden retriever, and the other, a middle-aged Bassett hound. The Golden retriever had more severe signs, including not eating, not playing, lethargy, and coughing. The Bassett hound was only mildly affected, but the pet owner was concerned enough to bring both dogs in. As both dogs were coughing, we elected to do chest X-rays. Being that these dogs were from Minnesota, where a severe, systemic fungal infection called blastomycosis can be found, I was worried the fungal infection may have spread to their lungs.


Unfortunately, chest X-rays in both dogs showed lung nodules suggestive of either cancer or a fungal infection. After doing a lung aspirate (a procedure where we suck a few cells out of the tissue to determine what is occurring), we identified an aggressive cancer called adenocarcinoma.

The owner was obviously heartbroken by the double dose of bad news. Having two unrelated dogs affected by cancer simultaneously is very rare, and as a result, I bluntly told the owner that she should have the radon level in her house checked. (She confirmed that there were no smokers in the household, which would have been my first guess). Either that, or move out of the house completely. Whether or not there was a direct environmental cause-effect, I wasn’t able to identify, but it was enough to scare both myself and the pet owner.

Cancer, a mutation in a cell’s genes, can be caused by random mutation, chemical or toxin exposure, genetics, or have no known cause at all. While there’s no distinct link with radon and cancer in pets, previous studies have shown that animals that have more exposure to paints, chemicals, and urban areas have a higher incidence of cancer. Currently, there are research studies being conducted to see if there is a link between second-hand smoke and lung cancer in pets.

Unfortunately, cancer is the leading cause of death in pets, and accounts for approximately 50 percent of the demise of pets that are over ten years of age. We’re likely seeing an increase in cancer due to multiple reasons: because pets are living longer than ever (thanks to the high quality of veterinary medicines now available); because we’re able to diagnose cancer better (thanks to advanced procedures like MRI, CT, abdominal ultrasound, etc.); and because of genetics (the more popular a breed becomes, the higher the risk of cancer!). 

Some common types of cancer we are seeign more in dogs include skin masses (e.g., mast cell tumor, melanoma, fibrosarcoma); lymph node cancer (e.g., lymphosarcoma); breast cancer (e.g., mammary gland adenocarcinoma); cancer of the head/neck/mouth (e.g., squamous cell carcinoma, melanoma, adenocarcinoma); cancer of the abdominal organs, such as the spleen and liver (e.g., hemangiosarcoma, adenocarcinoma); and even bone cancer (e.g., osteosarcoma).

Signs of cancer include:

  • Weight loss
  • Inappetance or anorexia
  • Difficulty breathing
  • Fever
  • Bloody noses or abnormal bruising or bleeding
  • Difficulty urinating or defecating
  • Abnormal swellings that continue to grow in size
  • Non-healing sores
  • A lameness that does not resolve
  • Masses over the mammary area
  • Acute seizures

Obviously, this list isn’t inclusive, but the point is, if you notice anything unusual in your pet, get to a veterinarian, pronto! Unfortunately, dogs don’t show their signs of cancer until it is severe or end-stage, so the prognosis for cancer varies with the type, location, and degree of metastasis (cancer spread).

The diagnosis of cancer is made based on physical examination, blood work, X-rays, ultrasound with aspirates or biopsies, CT, or MRI. Most types of canine cancer are not "curative," depending on the grade of severity of the cancer. Treatment may include a combination of surgery or surgical debulking (making it smaller via surgery but not curing it), radiation therapy, chemotherapy, or immunotherapy. Your veterinarian may refer you to a board-certified oncologist (cancer specialist) for further workup. Your oncologist can then discuss the overall success rate of treatment options, which again, depends on the type, extent, malignancy, and spread of the cancer. Lastly, remember that while there is a lot of bad or erroneous information on the Web, there is also some helpful info. Some of my favorite veterinary sites are: Veterinary Cancer Society, American College of Veterinary Internal Medicine and American Veterinary Medical Association. (Ed. Note: There is also a petMD cancer topic center for both dogs and cats.)

Having a dog with cancer is devastating.  I’ve had to personally experience this myself with JP. That said, JP survived the odds. I was quoted that he’d only live 4-10 months, and he’s at 11 months so far! Don’t get false hope, however. This is extremely long, and I’ve been grateful for every day since then. After all, each day is icing on the cake.

Know that if your pet is diagnosed with cancer, there are many options, ranging from humane euthanasia to steroid therapy to more aggressive treatments. Find a veterinarian or veterinary oncologist who will work with you to make the best decision for you and your pet.

Dr. Justine Lee

Pic of the day: Puppy Love by ArcheiaMuriel

puppy face, black dog, dog with cancer, dog cancer, cause of cancer in dogs, lymphosarcoma

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