Cancer is the leading cause of canine death and according to Morris Animal Foundation the percentage of dogs with cancer is quite high with 1 out of every 4 dogs likely to die from cancer. About 50% of dogs that are over 10 years old die of cancer or related issues and it’s the cause of death in 23% of dogs of all ages with lymphoma as the leading cancer diagnosed. The good news is that about 60% of cancers in dogs are curable if detected in the early stages.
Meaning of cancer
Cancer is an umbrella word for different types of diseases that result in purposeless and uncontrolled replication of cells either on or within the body. These uncontrolled cell growth result in masses (tumor) that are either visible on the dog or on the affected internal organs which could either remain in the affected area (localized) or metastasize (spread) to other parts of the body.
Tumors that metastasize are malignant while the localized tumors are largely benign; tumors are usually named after the tissue or body part that it originated from. This uncontrolled cell growth happens when the immune system has failed in its responsibility to check the wild cell replication.
Causes of cancer
A high incidence of canine death from cancer has been linked to canine longevity (cancer appear to be a disease of older dogs) due to vaccination, nutrition, parasite control etc. That is better care results in longer life which increases the tendency to develop cancer as a result of old age. While there are no exact scientific data that can conclusively prove the causes of canine cancer however the following have been found to play a part in the causes of canine cancer:
Obesity: while obesity has been shown to increase the risk of cancer in humans, recent researches has also shown that obesity is a risk factor in dogs.
Genetics: just as in humans it has been established that certain dog breeds are genetically predisposed to cancer compared to some other breeds. For instance Rottweiler and Golden retriever are at high risk of lymphoma and osteosarcoma while Chihuahuas, Pomeranians and Dachshunds are at low risk.
Chemical carcinogens: topical insecticides and herbicides are known to increase the risk of bladder cancer and lymphoma respectively
Sun light: ultraviolent radiation from the sun is known to induce canine cancer with short haired breeds at high risk or afflicting sparely haired and non-pigmented areas of any breed such as the belly, head and neck.
Other causes of canine cancer include vaccinations and fillers and preservatives in dog foods.
The best way to treat cancer is to prevent it and at worse to be well informed in order to be able to detect it a very early stage. Early warnings of dogs with cancer are:
- A growing lump: lumps that appear on dogs should be given close attention even though not all lump or bumps are cancerous but benign lumps almost always stay the same in terms of size but once the lump begins to grow in size, then a vet’s attention should be sought as this is a serious red flag associated with most malignant tumors (cancer).
- Unyielding weight loss: while a chronic weight loss does not necessarily suggest cancer in dogs as there are many possible reasons why a dog may be experiencing chronic weight loss but one thing that a chronic loss of weight clearly suggests is that the dog should be seen by a vet for further examination. Lots of cancer patients experience weight loss.
- Oral bleeding and/or bad breath: bad oral odor that was never noticed before should be given attention as it could be an indication of oral tumor that is building up in the dog’s mouth. It may also lead to bleeding from the mouth.
- Cough: while there are many different possible causes of coughing in dogs, a non-productive dry cough can also be an indication of lung cancer in dogs.
- Bleeding or wounds that refuse to heal: bleeding should only realistically occur when a dog suffer trauma or has a cut but continuous bleeding e.g. from the anus, mouth or nose or a wound that will not heal should be immediately brought to the attention of the vet.
- Swollen belly: while a dog may put on extra weight as a result of eating more than usual however if the dog suddenly starts growing a big belly this could indicate a growing or ruptured tumor that should be checked by the vet.
- Vomiting and/or diarrhea: tumors associated with gastrointestinal tract will often cause chronic diarrhea and vomiting.
- Lameness: bone cancer in big sized dog breeds is associated with unexplainable or strange lameness.
- Other signs of dogs with cancer include difficulty in eating and/or swallowing, loss of stamina, unusual difficulty in breathing, urinating or defecating. Observation of any of the early warning signs of cancer in dogs could make the difference between life and death for the dog.
Most common canine cancer
There are different types of canine cancer but some types of cancer are more prominent than others such as:
Skin cancer: dog skin cancer is one of the most common types of canine cancer and when combined with mammary cancer in dogs they account for a total of 58% of the entire canine cancer. The most common skin tumor in dogs is mast cell tumor which is about 20% of canine skin tumors which is frequently seen in middle age/older dogs and in some breeds such as Boxers, Labrador retriever and Boston terriers.
With early detection, proper diagnosis and prompt treatment the prognosis is fairly good. Death from malignant tumor is usually because of metastasis to other tissues of the body.
Mammary tumors: this is tumor of the mammary gland and is the leading cause of cancer in female dogs of between 6-10 years of age and there is a 20-40% chance that benign mammary tumors will become malignant.
The prognosis of mammary tumor is not very encouraging because at the time of diagnosis about 50-70% of dogs with malignant mammary cancer will already have experienced metastasis and with the disease already in an advanced stage.
Lymphoma: malignant lymphoma is one of the most common canine tumors originating in the lymphoid tissues such as bone marrow, spleen and lymph nodes and it is commonly seen in middle age to old age dogs of over 5 years. It accounts for 5-7% of all canine tumor afflicting as much as 24 out of every 100,000 dogs.
Lymphoma can afflict any breed but some breeds are more vulnerable such as Saint Bernard, Bull Mastiffs, Basset Hounds, Airedales, Scottish Terriers, Boxers and Bull dogs while Pomerians and Dachshunds are at low risk.
With chemotherapy a remission of about 60-90% is achieved is a favorable prognosis.
Tumor of the mouth: oral tumor is responsible for about 6% of all canine tumors and among all the different oral tumors that afflict dogs melanoma is the most common followed by fibrosarcoma, squamous cell carcinoma and adenocarcinoma. Melanoma affects the tongue, gums, palates and lips of the dog. It affects dogs of all ages but more frequent in dogs within the age bracket of 7-11 years old.
Early detection of lymphoma when it is very small in size offer the best prognosis since the risk of metastasis increases with the size of the tumor.
Bone cancer: osteosarcoma is the most common bone tumor seen in dogs and it usually afflicts the long bones of the limbs compared to other bones such as the skull or the spine. This tumor is locally aggressive destroying the bones as it develops and often metastasize to the lungs.