All pets (like all people) have to die of something eventually, and the options are basically one of four possible causes: trauma, infectious disease, degenerative disease or cancer.
In the past fifty years, pet deaths from trauma have been reduced by enforcing laws and changing behaviour so that pets are kept under more control (roaming dogs are seen less commonly than in the past). Medical advances, including vaccines and antibiotics, have significantly reduced the incidence of infectious diseases (caused by parasites, viruses and bacteria). This means that pets are more likely to live for longer than in the past, and they’re more likely to eventually die of the other two causes: degenerative diseases (ageing) and cancer.
Just as it’s important for us humans to be aware of cancer, with public health campaigns about breast cancer in women, prostatic cancer in men, and a range of others too, it makes sense for pet owners to know the basics about common animal cancers. It helps to recognise the early signs (treatment is more effective when carried out sooner), and better again, it’s worth learning about how to reduce the risk, where possible.
To understand cancer, the terminology is important. Cancer is the uncontrolled growth of abnormal new cells: the term “neoplasia” means “new cells”, and the term tumour (meaning “swelling”) is also used. New cells and swellings can be “benign” or “malignant”.
Benign neoplasia or tumours are relatively harmless. In some cases, they can be left alone, with no treatment needed, and in other cases, surgical excision usually allows a complete cure.
Malignant neoplasia or tumours are different: this is what we call “cancer”. These cannot be left alone, as they will steadily progress or spread to other parts of the body. Surgical excision may not provide a complete cure and follow up chemotherapy or even radiation treatment may be needed.
It’s interesting to compare human cancer and cancer in pets. Breast cancer is the most common malignancy in women and the mammary gland is a common cancer location in female dogs and cats too. In contrast, carcinoma of the prostate gland, a very common condition in men, is rare in dogs. Cancers of the lung and large bowel, the next most common human tumours, are not often seen in pets, while soft tissue sarcomas (e.g. lumps under the skin), which are rare in humans, are commonly seen in dogs and cats. We still don’t fully understand why these differences exist, but it’s very likely that it’s due to the different genetics between the species.
In pets, the first form of cancer prevention is gained by breeding cancer-free animals in the first place. Some cancers have a confirmed genetic background: some breeds have higher rates of specific cancers. As an example, cancer (of various types) is one of the leading causes of death in Flat-Coated Retrievers, causing nearly 70% of the breed to die prematurely. Other dog breeds with a higher incidence of cancer include the Bernese mountain dog, Irish wolfhound and the Boxer. As well as this specific breed related tendency, bone cancer (osteosarcoma) is seen far more commonly in large or giant dogs, generally.
There is no genetic testing for most pet cancers, so the best option is to work from basic principles: find a reputable breeder who will allow you to look at your chosen pet’s ancestry to see if any types of cancer are common. If care is taken to only breed from cancer-free lines of dogs and cats, over time, the incidence of genetic-linked cancer will reduce. This is not as easy to do as you might think, given that most cancers are age-related, and most pets are used for breeding when they are young, before cancer has had time to develop. However if efforts are made to focus on the big picture (e.g. not breeding from offspring whose parents developed cancer), change is possible.
The top ten cancers in pets
1. Mammary cancer is very common (affecting around 25% of unspayed female dogs), but the good news is that it is almost completely prevented by early spaying (e.g. before a female reaches two years of age).
2. Lymphoma, or cancer of the white blood cells producing tissue in the body, is the next most common cancer, often causing vague signs of illness at first.
3. Splenic haemangiosarcoma is a cancer of the spleen, common in medium and large breeds of dog when they get older.
4. Osteosarcoma is a type of bone cancer, with signs starting as a lameness that gets steadily worse.
5. Mast cell tumours often start as lumps and bumps affecting the skin:
6. Malignant tumours in the mouth: inspecting your pet’s mouth regularly (eg monthly) is the best way to spot these early.
7. Squamous cell carcinoma of the ears or nose of white pets: sun block applied to their ear and nose tips on sunny days reduces this risk.
8. Cancer of the stomach or intestines can cause unexpected loss of appetite, weight loss, and signs of digestive disturbance.
9. Liver and lung cancer. The liver and lungs filter out tumour particles that pass through them, so they are common locations for cancer spread (metastases)
10. Soft tissue sarcomas often start as lumps under the skin.
The common theme of most of these cancers is that prevention is difficult, but early diagnosis allows early treatment, which is more likely to prolong your pet’s life. If your pet develops lumps or bumps, if they go off their food, if they lose weight, if they have any odd signs (such as lack of energy, coughing, or repeated digestive upsets), don’t waste time. Get them checked by your vet.
