Cancer. It’s a word that strikes fear into the heart of many pet owners.  One in four dogs will be affected by cancer, and with the disease being the biggest killer of dogs over the age of 10, it’s a significant threat to the wellbeing of our pets. As in people, catching cancer early is critical in helping to beat the disease, so it’s important you know what to look out for in your pets…

By Farrah Owens, Animal Health Trust

To start with, cancer is not just one disease, it’s actually 200 different types of disease. There are certain cancers which are more commonly seen in dogs, and are particular aggressive, like mast cell tumours – a form of skin cancer, lymphoma – a tumour of the lymph nodes, osteosarcoma – a tumour in the bones and oral melanoma – the most common tumour of the mouth.
Alongside this, there are some breeds known to have an increased risk of developing a certain type of cancer, like Flat- Coated Retrievers, German Shepherd Dogs, Boxers, Golden Retrievers and Labrador Retrievers to name but a few. But cancer really isn’t picky – it affects all dogs, young and old, purebred and crossbred.

You know your dog better than anyone. All those early morning walks and cosy afternoons in front of the fire add up to a lot of time spent with them. This means you are best placed to notice subtle changes in them. So, let’s take a look at some common signs of cancer you can look out for in your dogs. Some warning signs of cancer in dogs are very similar to those you would expect in people – abnormal lumps, bumps or swelling that hang around or grow, a sore that won’t heal, unusual bleeding, weight loss and loss of appetite. You may notice a nasty odour, or that your dog is having difficulty doing everyday things like eating, swallowing, breathing, going to the toilet or even walking.
Every dog is different so keep an eye out for subtle changes in them – an excessive thirst, hesitation to exercise or loss of stamina can all show that something is wrong.
Of course, not every dog showing these signs will have cancer but, if your pet does have any of these signs, it’s worth a trip to the vets for further investigation. Remember, just like in people, catching cancer early drastically reduces its risk. Finding a cancer early gives you a head start in treating it successfully, so if you are concerned about any changes in your pet, book a vet’s appointment as soon as you can.

Don’t panic! Although a cancer diagnosis can be terrifying, there are often a variety of treatment options available aimed to either cure your pet, or provide a better quality of life. These are most often tolerated very well by our four-legged friends. It may surprise you but nasty side-effects known to effect people such as vomiting, hair loss and fatigue are seldom seen in dogs undergoing chemotherapy.
Remember that our dogs live shorter lives than us, with life expectancy ranging from eight to 16 years, depending on the type and size of dog. Because of this cancer treatments often aim to provide a good quality of life, as well as extending it.
The way in which vets can treat cancer has advanced in leaps and bounds since the turn of the millennium. Many treatment options available to people are also available for our pets. Many dogs are going on to live happy, healthy lives after a cancer diagnosis and treatment. There are a number of facilities across the UK with trained veterinary specialists who only treat cancer in small animals. So wherever you live, help will not be far away.
Just like us every dog’s cancer, and therefore treatment, is different. Often it is necessary to use more than one type of treatment to get the best results for each patient. This can be a combination of surgery, chemotherapy and radiotherapy. Surgery alone can cure tumours that are removable and have a low risk of spreading elsewhere.
However, sometimes it is not possible to remove all the tumour cells, in which case radiotherapy or chemotherapy might be recommended.
Chemotherapy is used to target cancer cells anywhere in the body, and is used when there is a high risk of the cancer spreading. In dogs, chemo might be given in either
tablet form or as an injection.
Leading veterinary charity, the Animal Health Trust, spoke to dog owners whose pets had undergone cancer treatments. It found that owners were very happy with their pet’s quality of life during and after treatment. Of the owners of dogs with cancer treated at the charity’s Small Animal Referral Centre, 86% were happy that they had pursued radiotherapy, 93% would choose it as a treatment option again and 91% would recommend radiotherapy treatment for dogs to their friends.
The Animal Health Trust is the only UK charity with a dedicated research programme focussed on beating cancer in dogs. Through its research, the charity aims to prevent dogs from losing their lives to cancer, and reduce the number of dogs that develop cancer.
The charity concentrates its research on the most common and aggressive cancers in dogs, such as mast cell tumours, known to affect more than 12,000 dogs in the UK last year, and lymphoma. Dogs diagnosed with the most common form of lymphoma have an average survival time, without treatment, of just four to six weeks.

We know that a common reason dogs die from cancer is because of tumour spread, or ‘metastasised’ as it is more formally known. So the Animal Health Trust has spent many years researching this to learn more. Its research has shown that the behaviour of a tumour depends upon how the tumour develops and where it is in the body.
As an example, let’s talk about mast cell tumours – a common cancer of the skin that can be highly aggressive. Some dogs are considered cured after surgery alone. However, for some dogs additional treatments might be recommended such as chemotherapy or radiation therapy.
These treatments are used to ‘mop up’ very small amounts of tumour that might remain after surgery, or where testing of the tumour has indicated that the tumour is aggressive and has a higher risk of spread elsewhere in the body. Chemotherapy might also be recommended to slow further spread if disease has already been found elsewhere in the body. Currently it is difficult to predict which patients might benefit from these additional treatments as there are only limited tests available to predict how an individual tumour may behave.
Dr Mike Starkey, Head of Cancer Research at the Animal Health Trust, said “Our work is so very important because research is the only way to beat cancer. By studying mast cell tumours we can begin to understand why some spread and others don’t, and why some respond to treatment and others won’t. We aim to identify new treatments that will enable hundreds of thousands of dogs to survive aggressive tumours.”
And the charity’s research is already taking huge steps forward in the fight against
cancer. Using equipment funded by the Kennel Club Charitable Trust and working with The University of Liverpool, Dr Starkey and his team have discovered genetic changes in mast cell tumours that enable them to spread. The research has shown that by looking at some of these changes, it is possible to recognise a tumour that will spread with an accuracy of 90%. With tumour spread being the main reason so many dogs lose their lives to cancer, this is a significant breakthrough for dogs and their owners.
Leading on from this discovery, it will hopefully be possible to develop a test which will accurately tell vets if a mast cell tumour is likely to spread, and how best to tailor therapy for each dog with this type of tumour.
There’s even more good news on the horizon for Labrador Retrievers and Golden Retrievers, two of the UK’s most popular breeds and two breeds more susceptible to developing mast cell tumours.
Animal Health Trust scientists have looked at the DNA of these dogs with mast cell tumours, and have identified a change in the DNA, or a ‘risk’, carried by 70% of Labradors and Golden Retrievers. If a dog has two copies of this risk in its DNA, it is three times as likely to develop a mast cell tumour than dogs that carry just one copy.
There is still work to be done – researchers need to identify other genetic risk variants for mast cell tumours, but the Animal Health Trust hopes that, in time, a screening test can be made available to benefit more than 100,000 dogs in the UK.
Cancer remains one of the biggest threats to the wellbeing of dogs, but through research, scientists are taking major strides forward in finding ways to beat it. In time, it will be possible to reduce the number of dogs that develop particular cancers, and, significantly reduce the number of dogs who die from the disease.