Revealed: Dogs are most at risk of dying from cancer – with medium-sized pups topping the list

Overall, medium-sized dogs have a higher risk of developing cancer than the very largest or smallest breeds, study foundOverall, medium-sized dogs have a higher risk of developing cancer than the very largest or smallest breeds, study found

A new study shows which dog breeds are most at risk of dying from cancer – and it’s not good news for owners of medium-sized puppies.

By studying mortality data for dogs from three different countries, a biologist in California found that the flat-coated retriever has the highest risk of cancer mortality.

Overall, medium-sized dogs have a higher risk of developing cancer than the very largest or smallest breeds, the study found.

The Scottish Terrier, Bernese Mountain Dog and Bullmastiff are also at ‘significant risk’ of dying from the disease, the expert found.

Meanwhile, breeds with the lowest risk of cancer include Pomeranian, Miniature Pinscher, Shih Tzu and Chihuahua.

Overall, medium-sized dogs have a higher risk of developing cancer than the very largest or smallest breeds, study finds

Dogs are the most and least likely to die from cancer

MOST LIKELY TO DIE FROM CANCER

  1. Flat-coated retriever (60% chance of dying from cancer)
  2. Bernese Mountain Dog (50%)
  3. Bullmastiff (approx. 45%)
  4. Staffordshire Bull Terrier (approx. 40%)
  5. Scottish Terrier (approx. 40%)

LEAST LIKELY TO DIE FROM CANCER

  1. Pomeranian (10% or less)
  2. Pekingese (10% or less)
  3. Miniature Pinscher (10% or less)
  4. Shih tzu (10% or less)
  5. Chihuahua (10% or less)

The study was conducted by Leonard Nunney, a professor of biology at UC Riverside in California, and published in the Royal Society Open Science.

“Cancer is one of the leading causes of death in domestic dogs, but deaths from cancer vary widely by breed,” he says in his article.

‘Some of these breed differences in cancer risk may be due to the effects of inbreeding.’

Professor Nunney analyzed dog mortality rates based on three different data sets – one each from the US, Britain and Finland.

For the results, he looked at dog breeds that appear in at least two of the three data sets – 85 breeds in total.

He found that the smallest dogs, including Pomeranians, Miniature Pinschers, Shih Tzus and Chihuahuas, have about a 10 percent chance of dying from cancer.

Dalmatians and Bulldogs were among those at slightly higher risk – about 20 percent.

By comparison, many relatively large breeds, such as the Burmese Mountain Dog and Bullmastiff, have a 40 to 50 percent chance of dying from cancer.

But the Flat-Coated Retriever – a hunting dog breed native to England – had the highest cancer mortality rate, at about 60 percent.

The expert discovered that the breed develops a type of sarcoma at a higher frequency than it should have for its size.

Despite the general trend for small breeds to be at lower risk, the Scottish Terrier is a small breed with an unusually high risk of death from cancer compared to other small breeds.

‘Terriers generally get more cancer than expected for their size,’ Professor Nunney said.

In the flat-coated retriever (FCR), the mortality rate from cancer is significantly higher (approximately 60 percent). The Bernese Mountain Dog (BMD) has a risk of about 50 percent, while the Bull Mastiff (BulM) has about 45 percent and the Staffordshire bull terrier (SBT) and Scottish terrier (ScoT) about 40 percent. Breeds with low cancer rates include bulldog (BulD) and dalmatian (Dal)

The Flat-coated Retriever – a hunting dog breed originating from England (photo) – had the highest mortality rate from cancer

Many relatively large breeds, such as the Burmese Mountain Dog (pictured) and Bullmastiff, have a 40 to 50 percent chance of dying from cancer

Just like humans, dogs develop cancer due to genetic factors and environmental stressors.

It’s common for cells to acquire errors or mutations as they divide and form copies of themselves – the process that can lead to cancer.

Larger animals, and those that live longer, have more cells and a longer lifespan during which these cells divide – so they should have more opportunities to acquire mutations that eventually become cancer.

‘Research in humans shows that tall people get more cancer than short people,’ says Professor Nunney.

‘It involves an increase of about 10 percent over the baseline risk for every 10 centimeters of height.’

However, the very largest breeds, such as Great Danes, have less cancer than medium-sized breeds, the results show.

This is due to a yet unexplained phenomenon: the life expectancy of dogs decreases as body size increases.

‘For every kilo increase in typical breed size you lose about two weeks of life,’ Professor Nunney added.

‘A very large dog, you’re lucky if it lives longer than nine years, while small dogs can live up to fourteen years.’

Breeds with the lowest risk of cancer include Pomeranian (pictured), Miniature Pinscher, Shih Tzu and Chihuahua

Scottish terrier (pictured) is an example of a small breed with a high risk of death from cancer, compared to other small breeds

Cancer is primarily a disease of old age, so due to a shorter lifespan, the largest dogs have a lower risk of cancer than medium-sized dogs.

In other words, larger dogs may not die from cancer as often as medium-sized dogs, but they are likely to have a shorter lifespan anyway.

Professor Nunney warns that some breeds may have had an increased risk of cancer due to inbreeding – the mating of closely related dogs together, usually of the same breed.

Mixed-breed dogs live about 1.2 years longer than purebred dogs of similar size, a previous study found. This indicates that a decrease in inbreeding levels leads to a longer lifespan of dogs.

“Inbreeding (and the associated loss of genetic diversity) is a known cause of increased incidence of hereditary diseases,” the expert adds.

Like the symptoms in humans, the warning signs of cancer in dogs include lumps and bumps, abnormal discharge, non-healing wounds, weight loss, change in appetite, and coughing or difficulty breathing.

According to the NC State University Veterinary Hospital, up to 80 percent of skin lumps in pets are not cancerous.

“But consulting with your vet is the only way to be sure,” it says.

WHICH ANIMALS GET CANCER?

Cancer appears to affect all animals, but is difficult to study in wild populations because they move frequently.

The most affected species include:

Tasmanian Devils

An unusual form of cancer has made Tasmanian devils an endangered species in their native Australia.

Unlike most cancers, which arise from genetic mutations, Tasmanian devil facial tumor disease (DFTD) is transmitted between animals through biting, aggressive mating or sharing food.

DFTD is most common on the face or mouth, but can spread anywhere in the body.

Nearly all affected animals die within six months due to an inability to eat or the spread of the disease.

Image shows a Tasmanian devil affected by a facial tumor, which is usually fatal

Nearly all those affected die within six months due to an inability to eat or the spread of disease

Dogs

Breast cancer is the most common form of the disease in female dogs.

Cancerous tumors almost always result in death of the animal, even with treatment, because they spread.

The majority of breast cancers in dogs are discovered during routine vet exams, but owners may notice:

  • Lumps or swellings around the nipples
  • Abnormal discharge from the breasts
  • Enlarged lymph nodes under the armpits or around the groin
  • If the cancer has spread, for example to the lungs, the dog may have difficulty breathing

Causes can be hormonal, genetic or diet-related.

Obese dogs appear to be more susceptible to breast cancer than their fitter counterparts.

Image a) shows a fish with a large melanoma on its side; b) is almost completely covered with melanoma; c) is a close-up of normal fish skin; d) is a close-up of melanoma on the skin of a fish

Fish

Coral trout, which live along the Great Barrier Reef, can develop melanoma.

Melanoma is the most deadly form of skin cancer.

The reef lies directly beneath the largest known ozone hole, exposing fish to high levels of UV light.

UV light is also the leading cause of skin cancer in humans.

Clams

Research shows that mussels can develop a form of leukemia in their hemolymph, which is similar to human blood.

Cancer cells drift away from the affected mussels and invade nearby animals, spreading the disease.

Source: Cancer quest

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