What exactly is cancer?
The term cancer refers to a large number of diseases all characterized by an abnormal proliferation of cells.
Most of the time, cancer results in the formation of a tumor although there are forms of cancer that do not. Cancer cells have the particularity of growing much faster than he althy cells. Unlike the latter, they multiply in an anarchic way and tend to invade neighboring tissues and detach themselves from the initial tumor to colonize other parts of the body by forming secondary tumors or metastases.
In dogs as in humans, there are various forms of cancer that can potentially develop from any cell in the body. Cancers are generally classified according to the tissue from which they develop (muscles, skin, organs).
Cancer is more specifically the result of genetic damage to cells. Within their nucleus, cells contain DNA that tells them when to grow, divide, work and die. The he althy cells of the dog's body are thus programmed to perform a given function and die to be replaced by new cells when they are too "old" to perform their function correctly. However, sometimes their DNA is damaged by various factors such as radiation, chemicals, hormones, certain infections or age. Some damage may even appear spontaneously.
When the DNA of cells is damaged, old cells that should have died to be replaced by new ones, survive and multiply without stopping. Most of the time, they form a mass - the tumor - without a precise function. Cancers can also release cells into the blood where they circulate freely in the body.
All mammals have immune protection to prevent or repair damage to cellular DNA that causes cancer to develop. However, these repair mechanisms are not perfect or infallible. Some individuals even have defects in these repair mechanisms, which are the cause of a higher incidence of cancer than in the general population. Some of these defects are also present at birth (this is also why we know that certain breeds of dogs are more prone to developing a particular type of cancer) when others develop with the time or under the action of environmental factors.
Why did my dog develop cancer?
It is estimated that approximately one in four dogs will develop cancer in their lifetime. Cancer is the leading cause of death in older pets. As the cells undergo more and more divisions as the animal ages, the possibility of an error (mutation) occurring during these cell divisions increases. As a result, the incidence of cancer increases with the age of the dog.
Many factors can influence the development of cancer, but just like in humans, it's impossible to really know why some dogs develop cancer and others don't.
In some cases, exposure to known carcinogens, such as exposure to UV rays from the sun, certain chemicals or cigarette smoke as part of the animal's passive smoking can play a role a role.Some cancers are favored by obesity, by certain chronic inflammations while others are influenced by hormones.
We also know that there is a genetic susceptibility to cancer in certain dog breeds.
What are the signs of cancer in dogs?
In most cases of canine cancer, the most obvious sign is a growing lump. This mass may ulcerate, bleed, or cause other effects such as compression of surrounding organs or tissues. However, since cancer can arise from any cell in the body, some internal tumors are not visible or even palpable to pet owners.
Chronic and unexplained weight loss can also be a symptom of cancer, but it is not systematic or specific to this disease. Abnormal bleeding, loss of spirit, unexplained fatigue, vomiting or diarrhea, presence of enlarged lymph nodes, appearance of cough, lameness, bad breath or changes in the animal's appetite can also be signs of cancer.
But, again, these symptoms vary according to the type of cancer and are not specific. Other pathologies can explain similar symptoms.
How is cancer diagnosed in dogs?
Your veterinarian may suspect cancer in your dog based on certain clinical signs or when certain symptoms are recalcitrant to conventional treatments. But, to confirm his diagnosis, the veterinarian will use additional tests such as imaging tests to detect internal tumors or blood tests.
To determine the nature of a tumour, it is then often necessary to obtain a sample of the tumour, either by fine needle aspiration, tissue biopsy or complete removal of the tumor. tumor. In some cases, exploratory surgery may be necessary.
Your veterinarian will send the sample collected to a specialized laboratory for examination by a veterinary pathologist. We are talking about a histopathological examination.
The histopathology report usually helps to determine if the tumor is benign or malignant. Malignancy is often described by tumor names ending in "-ome" such as carcinoma or sarcoma.
Determination of the origin and type of tumor, its degree of aggressiveness (grade) and its extent (extension assessment) in the animal's body will allow the veterinarian to determine the prediction.
What are the treatments for cancer in dogs?
The treatment most often considered and the most effective consists of surgical removal of the tumor. When the tumors are too large, too numerous or placed in places inaccessible to surgery or for cancers that do not cause no tumours, other treatments such as chemotherapy, immunotherapy or radiotherapy may be considered.
However, these treatments are not suitable for all types of cancer and can have side effects, generally much less marked than in humans, which can nevertheless be treated symptomatically.
In some cases, whether malignant or benign tumors, treatments and in particular surgery allow a long remission or even a complete remission. But, sometimes, the desired goal of treatment is not necessarily to achieve remission but rather to provide the best possible quality of life for your pet during the time he has left to live. The treatment options available vary greatly from one type of cancer to another and from dog to dog. They should be considered and discussed on a case-by-case basis with your veterinarian.