What dog breed is at the highest risk of cancer?

Getting a new dog can be an exciting time. When it comes to choosing the right dog for your family, there is a lot to consider. From the myriad of pure breeds to the variety of a mixed breed, there are so many options to choose from. While most people will consider the size, activity needs, and social skills of their prospective pooch, they may not immediately consider the cancer risk in that dog. As many breeds have associations with several health conditions, cancer is one of the disease possibilities that could impact your dog’s lifespan and your ability to enjoy your dog’s time with your family.

What is Cancer?

The cells within the body all serve a function. These may be to circulate around the body as part of the blood or immune systems, or they may serve as part of an organ or gland, contributing to its function, structure, and hormone production, for example. Cells have a lifespan however, and are constantly being turned over, with new cells replacing old, dying and defunct cells. Sometimes, cells mutate away from their intended purpose. Although the body’s defence systems are always on the lookout for abnormal and dying cells with a view to get rid of them, sometimes these mutated cells can evade these mechanisms. Where this occurs, they can replicate and grow over time, creating disease, lumps and distorted tissues.

When cancer develops, it can behave in either a benign or malignant manner

Benign cancers typically remain local to their site of origin. They may be slower to grow, or they may simply plateau in size. Benign cancers don’t spread (metastasise) to other parts of the body and remain a regional problem rather than a generalised problem.

This behaviour does not mean that they can’t be a health concern. Benign growths within organs or glands can still have a high impact on their function. Hyperadrenocorticism (Cushing’s disease) is a disease resulting from a hormonal imbalance created by a benign tumour in either the pituitary gland or the adrenal gland. Externally, some benign skin growths can ulcerate or burst, causing local pain and infection.

Malignant cancers on the other hand, are typically more aggressive. They may be faster to grow locally or are more damaging and invasive to the surrounding tissue structures. Malignant cancers are capable of metastasis. This is the process where cancerous cells seed across the body through either the blood stream or the lymphatic system, setting up secondary tumours elsewhere. These types of cancers can be devastating for the patient and can severely impact both length of life and quality of life.

Cancer in Dogs

Any dog, of any breed or breed mix, can get cancer within their lifetime. There is no way to test for or predict an individual dog’s likelihood of developing cancer. With manipulation and interference of genetic lines through breeding, though, humans have created many pure breeds of dogs. In doing so, some of these breeds carry an increased risk of developing cancer.

It is not fully understood what is involved with this increased risk, but it is expected that either a particular gene, gene combination, or gene mutation is responsible. This could be in the form of a dominant gene (where only one parent needs to carry it to put offspring at risk), a recessive gene (where both parents need to carry it to put their offspring at risk), or in the form of sticky genes (where genes for one characteristic are always associated with genes of a second characteristic). You can enquire with a prospective breeder about the lifespan and cause of death of a litter’s grandparents and great-grandparents to help inform you before purchase but there is currently no test available to screen for associated genes.

An extensive study in the UK demonstrated that 27% of pure breed dogs on average develop cancer. Other studies have shown that cancer accounts for 45% of the causes of death in purebred dogs over 10 years of age. Looking across the breeds though, this rate can vary greatly, with some breeds much more prone than others.

Breed Predispositions

The timeframe and intensity of a breed’s development can impact the risk for cancer. Modern breeds and those breeds with a smaller genetic stock, have a lower diversity within the gene pool compared to older breeds, which increases the likelihood of abnormal genes being passed on through bloodlines. Large breeds have an overall higher incidence of cancers than small breeds. One of the thoughts as to why this is the case, is related to the larger body size having a higher number of cells which increases the potential for a cell to go rogue.

The UK Kennel Club reported registered breeds with the highest cancer risk

The top three breeds being Irish Water Spaniel, Flat-coated Retriever, and Wirehaired Vizsla. Of the 20 most popular dog breeds in the UK, several have a predisposition to cancer: Golden Retriever, Labrador Retriever, Cocker Spaniel, Saint Bernard, German Shepherd, Irish Setter, Basset Hound, Great Dane, Beagle, and Boxer.

At the opposite end of the risk level

Pomeranians, Chihuahuas and French Bulldogs appear to have a lower rate of cancer among the popular breeds. Not all breeds have been studied equally though, and the rates of cancer in dogs can vary between countries, depending on the popularity of breeds and the genetic diversity across blood lines within that country.

Non-Genetic Influences

It is well known that genetics isn’t the only influencing factor in cancer risk. Just like cancers in humans, lifestyle and environment play a role too. Risks of cancer increase with age. Female dogs have a higher incidence of cancer than male dogs. Desexing, and the age at which it is done, can influence the likelihood of mammary cancers in females, and prostatic cancers in males. Obesity increases the risk of several types of cancer, which is a concern when an estimated 50% of dogs in the UK are classed as overweight or obese.

Aflatoxin, a mould that can grow in food, has been linked to cancer of the liver. UV exposure in pale-coloured dogs with thin coats can trigger skin cancer. The environment that the dog lives in can also contain carcinogens. Depending on location, and proximity to hazards, these can include tobacco smoke, products used on agricultural land and foods, such as pesticides and herbicides, and general air pollution.

Types of Cancer

As with humans, there are multiple types of cancer that can affect dogs, although some types occur more commonly than others. Cancers of the skin and soft tissues are the most common types according to claims made to insurance companies. Benign cancers are more common than malignant ones. Histiocytomas (a benign skin growth) is the most common overall, with lipomas (a fatty lump) and adenomas (glandular growths) also being very common.

In the malignant category, mast cell tumours, soft tissue sarcomas, lymphomas, and osteosarcomas are most common. Melanomas are also seen in small breed or black-furred dogs, and mammary carcinomas are common in unspayed bitches. Brachycephalic breeds have a higher incidence of central nervous system (brain and spinal cord) tumours.

Mast cell tumours can occur anywhere on the body as a raised, red skin mass. They can also affect internal organs, especially the liver and spleen. Beagles, Boxers, Retrievers, Bull- and Staffordshire Bull Terriers, Cocker Spaniels, Pugs and Schnauzers all feature on the list of breeds prone to this tumour type. Mast cell tumours can vary in their behaviour and are graded accordingly. This grading influences the prognosis for the affected dog.

Haemangiosarcomas are a type of soft tissue sarcoma that is seen more commonly in Retriever breeds, German Shepherds, Boxers and Bernese Mountain Dogs. These are usually internal cancers, often found on the spleen. They are more likely to occur in dogs over the age of 6 years.

Lymphoma is a cancer of the lymphatic system and can occur on internal or external lymph nodes. Retrievers, Airedales, Basset Hounds, Boxers, Bulldogs, and Saint Bernards are prone. In bones, osteosarcoma is more prevalent in Dobermans, German Shepherds, Retrievers, Rottweilers, Saint Bernards and the long-limbed breeds including Wolfhounds, Deerhounds and the Great Dane.

Detecting Cancer in Your Pet

The sooner a cancer is detected in your pet, the better chance that your veterinary team can assist you in achieving the most optimum outcome. Symptoms can vary depending on type, but can be categorised as external signs and internal, or systemic symptoms. Externally, if you notice sores on the skin that don’t heal, or lumps/swelling that persist or grow, you should get these assessed by your vet, even if your pet remains well or doesn’t seem affected by the lump. Changes to how your dog smells, especially if they are localised, are also worth investigating.

Systemic symptoms include unexplained weight loss, changes in eating and toileting habits, changes to breathing patterns (rate and/or depth), pain, reduced exercise tolerance, or other unusual behaviour. These could be explained by other non-cancerous diseases but require a veterinary assessment to determine the cause and severity.

For external conditions, your vet may take a biopsy of any sores or lumps. This can involve a conscious procedure using a needle which suctions cells from the mass or may involve a surgical biopsy under sedation or general anaesthetic. With internal or systemic conditions, your vet will likely recommend blood tests and some form of imaging, which may involve an ultrasound or a CT scan.

Prognosis

It is important to note, that despite many breeds having a higher rate of cancer, there are plenty of dogs within these breeds that never develop the disease. If your dog is unfortunate to get cancer, many can be treated and managed. Benign cancers such as histiocytomas and small or early malignant cancers, may be able to be cured by surgical removal. Non-removable benign growths may be able to be managed medically, such as with the Cushing’s disease-inducing pituitary and adrenal adenomas. It is therefore possible for many dogs to continue to live a normal life following diagnosis.

Where a malignant, or internal growth is found, there are a variety of surgical, chemotherapy, radiotherapy and immunotherapy options, just as with people. Your veterinary team can assist you with determining the best course of action for your dog. This may take into consideration expected success of treatment, your pet’s tolerance for coming to the vet clinic for treatments, their ability to take oral medication, expected side effects, and financial involvement.

Conclusion

The risk of cancer in dogs is determined by genetics, lifestyle and environmental factors. Across the pure breeds, Retrievers, German Shepherds, Boxers, and Beagles feature among the list of breeds at increased risk of cancer. Although many dogs of these breeds can live cancer-free lives, if they do get cancer, early detection is key to achieving an optimal prognosis. Many cancers can be surgically removed or managed to allow a normal life. Additionally, cancer treatments such as chemotherapy and radiotherapy may also be an option. Whenever you are concerned about your pet’s health, or notice a new lump, seeking veterinary intervention is key.