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The Cancer Mystery in Dogs: What Science Just Uncovered...
And tips on how to reduce your dog's cancer risk
Bryan Reisberg
March 13, 2025
The Cancer Mystery in Dogs: What Science Just Uncovered…
Big dogs, big problems? Not exactly. For years, scientists thought that the bigger an animal, the more cancer it should have—more cells, more chances for things to go haywire. But reality doesn’t play by those rules. Whales and elephants should be riddled with tumors, yet they aren’t. Meanwhile, tiny budgies have a reputation for getting kidney cancer. This contradiction, known as Peto’s Paradox, has stumped researchers for decades.
A recent study finally put this paradox to the test across 260 species—including mammals, birds, reptiles, and amphibians—and found that, yes, bigger animals actually do get more cancer. But here’s the twist: some species seem to have evolved built-in cancer-fighting mechanisms. Take elephants, for example. They have over 20 copies of a gene that helps suppress tumors, while humans only have one. So, size alone doesn’t determine cancer risk—it’s all about how an animal’s biology adapts.
For dogs, this raises an interesting question. We know that larger breeds like Great Danes and Bernese Mountain Dogs have shorter lifespans and higher rates of certain cancers. But why? Scientists think evolution plays a role—species that grow big slowly (like elephants) seem to have better cancer defenses, while those that bulk up fast (like giant dog breeds) may not have had time to develop the same protections. This could explain why smaller dogs tend to live longer than their larger counterparts.
We pulled data on the top 10 large dog breeds that are most susceptible to cancer:
Golden Retriever
High risk for hemangiosarcoma (1 in 5 chance)
Lymphoma (1 in 8 chance)
Boxer
Prone to mast cell tumors, brain tumors, and lymphoma
Bernese Mountain Dog
High risk for lymphoma and histiocytic sarcoma
Rottweiler
Commonly affected by osteosarcoma (bone cancer)
Scottish Terrier
Transitional cell carcinoma (bladder cancer)
18 times higher risk compared to mixed breeds
Great Dane
High incidence of osteosarcoma (bone cancer)
Saint Bernard
Frequently develops osteosarcoma (bone cancer)
Flat-coated Retriever
High risk for histiocytic sarcoma
About 50% of affected dogs succumb to this cancer
Boston Terrier
Prone to mast cell tumors
The study also found that how an animal evolves over time matters. Whales and dolphins, for instance, got big much faster than most mammals, yet they seem to have found ways to keep cancer at bay. Meanwhile, some species—like salamanders—regrow limbs, which means tons of cell division, potentially increasing their cancer risk. The big takeaway? Cancer isn’t just about size; it’s about how nature works around it.
So what does this mean for your pup? While we can’t rewrite evolution, understanding how some animals fight cancer naturally could help us develop better treatments for dogs (and humans). Naked mole rats, for example, almost never get cancer—studying them might lead to breakthroughs in veterinary and human medicine. In the meantime, the best thing we can do for our dogs is focus on nutrition, exercise, and regular vet check-ups—because while we may not have elephant-grade tumor-fighting genes, we do have science on our side.
While there's no guaranteed way to prevent cancer in large-breed dogs, there are several proactive steps that can help reduce their risk and promote overall health:
Tips on How to Reduce Cancer Risk in Your Dog
1. Prioritize a High-Quality Diet
Feed a nutrient-dense, balanced diet rich in antioxidants, omega-3s, and lean proteins.
Avoid ultra-processed foods and excessive carbohydrates, which can contribute to inflammation.
Incorporate cancer-fighting ingredients like turmeric, blueberries, cruciferous vegetables (broccoli, kale), and fish oil.
2. Maintain a Healthy Weight
Obesity increases inflammation and cancer risk.
Keep your dog at a lean body condition through proper portion control and exercise.
3. Minimize Exposure to Carcinogens
Avoid pesticides, herbicides, and lawn chemicals—studies link them to cancers like lymphoma.
Choose stainless steel or ceramic bowls over plastic to prevent chemical leaching.
Limit exposure to tobacco smoke, air pollution, and other environmental toxins.
4. Regular Veterinary Checkups & Early Detection
Schedule routine wellness exams (at least annually, or semi-annually for senior dogs).
Perform regular lump checks—early detection is key for mast cell tumors and other cancers.
Ask your vet about preventative screenings like blood tests or ultrasounds for at-risk breeds.
5. Spaying & Neutering at the Right Time
Neutering before 1 year old may increase certain cancer risks in large breeds (like osteosarcoma).
Work with your vet to determine the best timing based on breed and health factors.
6. Support Immune Health with Supplements
Omega-3 fatty acids (from fish oil or algae) help reduce inflammation.
Probiotics & prebiotics support gut health, which plays a role in immune defense.
Mushroom extracts (like turkey tail or reishi) have shown promise in cancer prevention.
7. Encourage Regular Exercise
Staying active helps regulate immune function and reduces inflammation.
Low-impact activities like swimming, hiking, or walking can be great for joint health.
8. Avoid Over-Vaccination & Overuse of Medications
Discuss with your vet about titer testing instead of unnecessary booster vaccines.
Avoid excessive antibiotics and steroids, which can weaken long-term immune function.
9. Reduce Chronic Inflammation
Chronic inflammation is linked to cancer development.
Anti-inflammatory foods, regular activity, and minimizing stress can help.
10. Consider Genetic Testing for High-Risk Breeds
Some companies offer cancer risk DNA testing to identify genetic predispositions.
This can help you monitor and adjust care based on their individual risk factors.
Bottom Line: While cancer isn’t entirely preventable, taking a proactive, holistic approach to your large dog’s health can significantly lower their risk and improve their longevity.
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