A woman holds her Labradoodle who has been screened for canine cancer as she looks out at the ocean wondering about the test results

Cancer in Dogs: Why Breed, Age and Gender Matter


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Sadly, cancer in dogs is just as common as it is in humans. In terms of numbers, roughly half of all dogs will develop some form of cancer after their 10th birthday, with lymphoma in dogs being the most common canine cancer. But don’t give up hope – it’s not all bad news!

As scary as cancer is there are several preventative measures. Many of them have been proven to statistically lower the chance of canine cancer. Let’s delve in deeper in symptoms, causes and prevention.

This Saint Bernard is among the giant breeds who's median age of canine cancer diagnosis is found to be earlier than in smaller breeds

What age does cancer start in dogs?

According the PetDx study, the median age at for dogs diagnosed with cancer is 8.8 years. (In case you’re double checking – median is the mid-point, meaning that half the dogs were below that age and half above).

The researchers highlighted that age, weight, breed and gender are all variables that can contribute to the age a particular dog is first likely to be diagnosed. They showed these factors correlate with specific median ages for cancer diagnosis in dogs.

Here’s what these figures look like:

  • 5 years. Median age of diagnosis in dogs weighing 75kg and over
  • 6 years. Median age of diagnosis in the Bulldog, Mastiff, Saint Bernard and Great Dane
  • 6.1 to 7 years. Median age of diagnosis in the Irish Wolfhound, Vizsla and Bernese Mountain Dog
  • 11 years. Median age of diagnosis in dogs weighing roughly 2.5 – 5kg
  • 11.5 years. Median age of diagnosis in the Bichon Frise

Looks like the Bichon Frise has the oldest median diagnosis age, according to this particular study anyway.

This bichon frise sits with his two favourite people, sisters who are his human family.

Further on timing – emergence of cancer in dogs

New research published this year shows that “purebred dogs were diagnosed at significantly younger ages than mixed-breed dogs”. The PetDx study that examined over 3,000 dogs also found “males diagnosed at younger ages than females, and neutered dogs diagnosed at significantly later ages than intact dogs.”

So, we know that age is a contributing factor to cancer in dogs as is genetic makeup. Further on the breed-related factors, giant dog breeds appear to develop cancer earlier on than smaller dog breeds. (Read about the biggest dog breeds in the world to get a snapshot of which dogs are considered ‘giants’.)

Perhaps the reason giant dogs get cancer sooner is because they have shorter lifespans. In other words, the bigger breeds must fit their whole lives into a shorter time frame. It’s as if their lives are sped up. Here’s the dog to human age converter – have a look see how bigger dogs age faster:

Read this PD Pet Insurance dog age chart to see how big dogs age faster than little ones

What is the leading cause of cancer in dogs?

As with humans, there is a range of factors that can contribute to cancer in dogs. In addition to age, these include genetics, obesity and environmental factors, to name a few.

Let’s take a closer look at the above-mentioned risk factors:

  • Environmental factors

Research shows that, just like some human cancers, certain pet cancers are linked to exposure to sunlight or toxins like cigarette smoke, herbicide-treated lawns and household chemicals. Taking just the first two – UV radiation can be of especially higher risk to pets with light-coloured fur (read more in our Can Dogs Get Sunburn? Answers and Solutions article) and second-hand cigarette smoke has been linked to nasal cancer in longer nosed dogs and lung cancer in brachycephalic breeds.

  • Weight

Obesity is a leading health problem for pets today. A fat or obese dog is not just at a higher risk of developing cancer – often mammary cancer – but also diabetes, heart disease and joint problems.

  • Genetics

Certain breeds carry genes that make them predisposed to the development of cancer. These include Bernese Mountain Dogs, Boxers, German Shepherds, Golden Retrievers, Rottweilers and (for bone cancer) dogs with longer legs, like Great Danes, Irish Wolfhounds and Scottish Deerhounds.

You don't need to avoid these breeds, but it's important when buying one, to seek out ethical dog breeders that carry out health tests before breeding. 

What are the first signs of cancer in dogs?

Canine cancer can be sneaky to pick up on. The early signs of cancer in dogs are closely in step with those that people experience. Think lumps and bumps, swollen lymph nodes, decrease in appetite or weight and a general feeling of fatigue and exhaustion.

According to the PetDx study, cancer is the leading cause of death in adult dogs.

Then again, the signs may be less synonymous with cancer and could seem like something else… For example, limping, showing signs of pain, coughing or not breathing well and giving off strange new smells or discharges.

The big difference between us humans and our dogs when it comes to cancer is that we’re able to tell each other we’re feeling off or that something is different. Yes our dogs do let us know, but we need to be well tuned into their body language.

Essentially, we need to know how to speak dog to pick up on the cues.

A woman sits with her pets on a boulder looking out at the sea and hopes that the lymphoma in her dog will be able to be treated and managed

What is the most common cancer in dogs?

Lymphoma in dogs is widely known to be the most common canine cancer. The PetDx study echoes this in its data analysis from nearly 3,500 dogs examined and a long list of cancer types in dogs and/or location of the cancer on the dog.

Here are the top five types/locations of canine cancer on this list:

  • Lymphoma/lymphoid leukemia (979)
  • Bone osteosarcoma (664)
  • Mast cell tumour (565)
  • Hemangiosarcoma (292)
  • Soft tissue sarcoma (240)

Since lymphoma is the most common canine cancer, let’s look at this a bit more to find out what it is exactly.

Lymphoma in dogs

Lymphoma is a broad term for various cancers that develop in lymphocytes cells. These are white blood cells that travel through the bloodstream and tissues and, when they’re healthy, fight off infections. They produce antibodies to fight infections and help with other immune responses.

Of the 30 plus types of lymphoma in dogs, the four most common are:

  1. Multicentric lymphoma (lymph nodes)
  2. Alimentary lymphoma (intestinal)
  3. Mediastinal lymphoma (chest – thymus and/or mediastinal lymph nodes)
  4. Extranodal lymphoma (affects organs outside the lymphatic system, such as nervous system, skin and eyes, for example)

As the name suggests, lymphoma in dogs often presents in the lymph nodes becoming swollen. Often dogs will become dehydrated, tired and lose their appetite. For dogs who love to eat even non-edible things, a loss of appetite is a clear indicator something is amiss.

Of course, lymphoma in dogs isn’t the only reason for this. Read about some other possible reasons that can cause a dog to stop eating.

Veterinarian looks through a microscope that uses AI technology for slide reading results

Prevention is better (and cheaper) than cure

We all know the good old saying ‘prevention is better than cure’. But why? Well, usually when it comes to health it’s a lot harder getting better than staying healthy in the first place. Sometimes, it’s not even possible. Also, prevention tends to be a more affordable route in terms of energy and spend.

When it comes to a disease like canine cancer, prevention might really be the best cure on all these fronts.

According to the PetDx study findings, screening dogs every year for cancer, starting two years before they’re most likely to be diagnosed, could be a solution. Early diagnosis means early treatment with a much better chance of success.

For all dogs, that means getting screened aged seven, but for some dogs that develop cancers earlier on (generally speaking), the best age to begin cancer screening can be as early as age four.

What is the new blood test for cancer in dogs?

When it comes to canine cancer, there are several routes you can take on the path to prevention. Some help detect cancer cells in the earliest stages while others help rule out certain cancers developing altogether.

Several new blood tests look at DNA samples from dogs that are at higher risk of developing cancer. These early screenings can help you plan and manage your canine’s health through early detection. Ask your vet for advice on which test is most suitable for your dog according to its breed, health, age, weight and gender.

Another route often recommended by vets, animal advocates and animal rescues alike is dog desexing (or cat desexing). That’s because many types of cancer simply can’t happen when the common parts of the body they affect are removed.

However, this needs to be a decision made with your vet’s guidance. Have the procedure done too early and it can actually be a risk factor for cancer (some research has shown early desexing in particular breeds can increase the risk of developing certain cancers), whereas too late might be too late. Your vet will help guide you on timing, based on your dog’s breed, health and gender.

Watch our PD Pet Care Vlog for more on this with Dr Cath Watson:

Award winning dog insurance for a soft landing

Thankfully, not every lump and bump spells cancer in dogs. And if it does, scientific advancements in vet care are always evolving with new and better treatment options. However, as we mentioned already, prevention is better than cure. Sometimes that just means not leaving any out-of-the-ordinary symptom unchecked.

Keep up those routine vet visits and know that, for many of those unexpected vet visits that can rack up big unforeseen bills, you can have a soft landing thanks to pet insurance.

PD Insurance offers three award winning dog insurance and cat insurance plans. These help cover a wide range of vet costs for diagnosis, treatment, prescribed medication and more. Buy your pet’s plan online and we’ll give you one or more months of FREE pet insurance.

Click below to start your quote today.

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