Cancer in Dogs: The Guide

Dog Cancer

Questions

  • Can Dogs Get Cancer?
  • What Causes Cancer in Dogs?
  • The Signs of Cancer in Dogs
  • What Does Skin Cancer Look Like on a Dog?
  • Treating Cancer in Dogs
  • When it Might be time to Say Goodbye
Cancer in dogs is a very commonly seen medical problem. Many different types of cancer can affect dogs and whilst some are more serious than others, dogs of all ages can develop cancer. However, the longer your dog is alive, the more likely they are to develop it.
It’s extremely difficult for owners to navigate through a cancer diagnosis for their dog, but it’s important to remember that not all cancers cause death in dogs, many are treatable. This article will discuss the different types of cancer, their diagnosis and treatment, and some common questions owners have.

Can Dogs Get Cancer?

Dogs can develop cancer in their lives. It occurs when their bodies have an abnormal, uncontrollable growth, otherwise known as a tumour. It disrupts their organs and prevents them from functioning normally. Tumours can be benign or malignant.
Benign tumours usually grow slowly, putting pressure on surrounding tissues but they are not invasive. Malignant tumours tend to grow faster and invade the tissues around them and can spread (also called metastasize) to other parts of the body.
Dogs can develop many different types of cancer. Common types seen in dogs include skin cancer, mammary cancer (affecting the breast tissue and mainly seen in female dogs), and cancers affecting the digestive tract or other internal organs such as the lungs, liver or kidneys, or bones.

What Causes Cancer in Dogs?

Frustratingly, cancer often occurs for reasons unknown. The development of cancer can be influenced by many factors, some of which include:
  1. Genetics

  2. Age

  3. Infections and viruses

  4. Toxin or chemical exposure

  5. DNA mutations

  6. Excessive sun exposure

  7. Hormones

  8. Genetics - there are many studies documenting the role of genetics in cancer development

There are lots of forms of cancer linked to specific breeds, some of these include:
  1. Great Danes - Bone cancer

  2. Boxers - Mast cell tumours

  3. Boston Terriers - Mast cell tumours

  4. Cocker Spaniels - Ear cancer

  5. Golden Retriever - Lymphoma and hemangiosarcoma

  6. German Shepherd - Hemangiosarcoma

  7. Beagle - Bladder cancer

  8. Bernese Mountain Dog - Mast cell tumours and histiocytic sarcomas

  9. Rottweiler - Osteosarcoma, Lymphoma, soft tissue sarcomas, mast cell tumours, transitional cell carcinoma

Hormones can also Cause Cancer in Dogs


Sex hormones are thought to influence certain types of cancer. Female dogs who are spayed later in life have a higher risk of developing mammary adenocarcinomas with every season they have. It’s also thought that exercise, diet, and body weight all influence the development of cancers to some degree.
There are hormonal and inflammatory changes that occur in sedentary and overweight dogs which are believed to affect the quality of life and life span. This study focused on cancer and other chronic illnesses, the cancer rate overall was very similar, however, the age at which cancers and chronic disease developed was a lot younger for overweight dogs.

The Signs of Cancer in Dogs

Cancer can occur in any part of the body. This means that symptoms are very variable depending on the location. Some cancers are very aggressive and cause sudden changes. Others are slow growing, and changes are very subtle. A lot of the time, the first telltale signs are very generalized and nonspecific, so it can be difficult to pick up on a diagnosis. Arrange an appointment with your vet if you see any of the following:
  1. Weight loss

  2. Reduced appetite

  3. Vomiting

  4. Diarrhoea

  5. Lethargy

  6. Weakness

  7. A mass present

  8. Abnormal swelling

  9. A wound that takes longer than usual to heal or becomes ulcerated.

  10. Change in breathing rate /difficulty breathing.

  11. Cough

  12. Lameness

Lots of these can be easy to miss or dismiss as something trivial. If you notice any changes to your dog, it is best to book an appointment to be seen as treatment options and prognosis are often more favourable if diagnosis is made early.  

What Does Skin Cancer Look Like on a Dog?

Skin cancer in dogs can take various forms. This can include:
  1. Masses

  2. Scabs

  3. Wart-like lesions

  4. Ulcers

They can be a range of different colours depending on which parts of the skin are affected and how well the tumour is established. They are often red, brown, black, pink, or grey. If you spot any masses or lumps or strange lesions on your dog, consult your vet immediately.

Treating Cancer in Dogs

The three main types of treatment options for dogs are - surgery, Chemotherapy, and radiotherapy. There are some other newer therapies such as immunotherapy, cryosurgery, and photodynamic therapy but these are less commonly used.

Surgery


Surgery is a popular option for skin cancers or any distinct tumours in accessible locations. Usually, a biopsy is taken to identify the mass and plan the surgery, deciding appropriate margins. Often samples of local lymph nodes or other tissue are taken to assess if metastases have occurred.
Surgery can also be used to debulk masses and reduce the size of them to prevent them from pressing on neighbouring organs and stopping optimal function. If this is done, the risk of recurrence is usually high.

Chemotherapy for Dogs with Cancer


Chemotherapy can be used for lots of different types of cancer. It involves using a combination of drugs to kill cancer cells or slow their growth. Some treatments are only administered by a vet, but some can be given at home. It is often used for widespread systemic cancers such as leukaemia or cancers where surgical excision is not possible. It can be done following surgery if complete excision is not feasible. Chemotherapy does usually cause side effects such as vomiting, diarrhoea, and reduced appetite.

Radiotherapy


Radiotherapy is usually carried out at referral practices. Cancer cells are killed using radiation. It is normally used to reduce the size of tumours rather than completely remove them. A general anaesthetic is usually required for treatments as your dog needs to be still.
Other treatments can be used such as anti-sickness medication or pain relief.

How Long Can a Dog Live with Cancer?


The life expectancy after a diagnosis depends on how quickly the cancer has been picked up and how far it has progressed. It also depends on the type of cancer present as some develop very slowly whereas others are extremely aggressive. 
Lots of cancers are staged depending on severity and this is usually based on things like local spread or systemic spread. Some dogs will go on to live healthy lives if full curative surgical excision is carried out. In some cases, the cancer is so aggressive that even with dramatic surgery (for example limb amputation with osteosarcomas) the prognosis is still poor.

When it Might be time to Say Goodbye

Knowing when the right time to say goodbye can be very difficult for owners. The most important thing when considering when might be the best time to put your dog to sleep is their quality of life. Owners will be able to assess if their quality of life is acceptable at home. Questions to consider when thinking about this include:
  1. Are they able to enjoy normal dog activities without being in pain or discomfort?

  2. Do they have a good appetite?

  3. Do they have more good days than bad?

  4. Can they rest and sleep comfortably?

  5. Are they getting distressed unduly?

  6. Do they dislike visits to the vet and get stressed and anxious?

  7. Are there side effects of the medication? 

As well as these questions welfare, in mind the Five Freedoms which are important reminders of the standard of animal welfare we should expect:
  1. Freedom from hunger and thirst

  2. Freedom from discomfort

  3. Freedom from pain, injury, and disease

  4. Freedom to express normal behaviour

  5. Freedom from fear and distress

There are lots of factors that will influence your decision. These include the presence of metastatic disease, concurrent health issues, risks and side effects of treatment, and cost of treatment.  
Always discuss your thoughts with your vet before making this decision. You will be able to gauge the quality of life your dog has, and your vet will be able to provide the clinical information required to come to the right decision. It is an incredibly hard choice to make, at any stage in your dog's life. Remember, if your dog is suffering, the most humane and kindest thing to do is to end that suffering and put them to sleep.
Cancer in dogs can be an extremely distressing time for owners and pups, but early detection is key. Look out for the signs and always consult your vet for further advice. For all the doggy essentials you need check out our range, in-store and online.