What is the prognosis for lymphoma?
The prognosis for lymphoma varies, depending on various characteristics that can only be determined by specialized testing. On average, dogs who receive no treatment (or are treated with prednisone alone) have an expected survival of four to six weeks. However, this is an average, with some dogs being euthanized or dying before the four-week point and some living past six weeks.
With chemotherapy, lymphoma can often be put into remission. While lymphoma is never truly ‘cured’, remission is a term that is used to describe the temporary resolution of all signs of lymphoma. The average remission with chemotherapy is eight to nine months, with an average survival time of approximately one year. Again, this is only an average; some dogs will die sooner, and some will live longer than one year. Your veterinarian may be able to provide more specific information on your pet’s prognosis if you pursue additional testing to characterize the lymphoma better.
What are the clinical signs of lymphoma?
In dogs with multicentric (systemic) lymphoma, the first sign of lymphoma is swelling of the lymph nodes. The lymph nodes in the neck, chest, armpits, groin, and behind the knees are often the most visible and easily observed. The dog’s owner may note swelling of these lymph nodes, or the veterinarian may first note them on a routine physical exam. Most of these dogs do not have any clinical signs of illness at the time of diagnosis, although they will often develop signs such as weight loss and lethargy if untreated.
In the other, less common forms of lymphoma, clinical signs depend on the affected organ. Alimentary lymphoma causes gastrointestinal lesions, resulting in vomiting, diarrhea, and weight loss. Mediastinal lymphoma creates lesions within the chest that take up space in the chest cavity, commonly resulting in coughing and shortness of breath. The effects of extranodal lymphoma vary significantly, depending on the organ involved.
Not all dogs with enlarged lymph nodes have lymphoma. Enlarged lymph nodes may also occur due to infections or autoimmune diseases, so your veterinarian will perform tests to determine the cause of your dog’s clinical signs.
The most common test to diagnose lymphoma is a fine needle aspirate (FNA). In this test, a veterinarian inserts a needle into an enlarged lymph node (or another organ) and removes a small number of cells. These cells are then examined under a microscope, looking for evidence of cancerous cells that indicate lymphoma.
If FNA is inconclusive or impractical due to the lesion’s location, your veterinarian may perform a biopsy. This involves the surgical removal of a tissue sample from the lymph node or lesion. This sample will be processed and examined under a microscope at a veterinary laboratory to look for the presence of lymphoma.
Your veterinarian will also likely perform baseline screening bloodwork to assess your dog’s overall health. There are two components to this bloodwork. A complete blood cell count involves examining the cell types within your dog’s blood and assessing quantities of red blood cells, white blood cells, and platelets. Serum biochemistry is used to assess the function of your dog’s internal organs.
If your dog is diagnosed with lymphoma, your veterinarian may perform additional testing to find out more information about the lymphoma and develop a treatment plan. These additional tests may include the following:
Your veterinarian may also recommend additional tests to determine the extent of your dog’s lymphoma. This testing commonly includes imaging such as radiographs (X-rays) or ultrasounds.
There are five stages of lymphoma. Stage I and II are rarely observed in dogs, while Stages III-V are.
Lymphoma is treated with chemotherapy. There are a variety of procedures used, but most consist of a variety of injections given every week. Fortunately, dogs tend to tolerate chemotherapy better than humans; they rarely lose their hair or seem to feel ill during chemotherapy. The most common side effects of chemotherapy include vomiting, diarrhea, and decreased appetite, though even these effects are not seen in all dogs. If chemotherapy is not an option due to patient factors or owner financial constraints, prednisone can be used for palliative care. Although prednisone does not treat lymphoma, it can temporarily reduce clinical signs and buy the pet some time.
Surgery and/or radiation may be appropriate for certain types of low-grade localized lymphoma, but most cases cannot be successfully treated with surgery or radiation.
Owners also need to know the difference between the terms “remission” and “cure.” Total remission means that all signs and symptoms of cancer have disappeared, but cancer could still be in the body. Partial remission means that some, but not all, signs and symptoms of cancer have disappeared. Remission, however, is different from a cure, which can be defined as elimination of the disease entirely.
Dogs with alimentary lymphoma, which affects the intestines, may present with vomiting, abdominal pain, anorexia, diarrhea, and weight loss.
Mediastinal lymphoma is rare. In this disease, either or both the thymus and the mediastinal lymph nodes in the area of the chest become enlarged, caused by high-grade malignant T lymphocytes.
Once cancer is a suspected, veterinarians get a definitive diagnosis by taking a sample of the affected organ. The most common diagnostic tool is something called a fine-needle aspiration, which extracts a sample of a dog’s lymph nodes or organs to be evaluated through cytology exam or by a histopathologic tissue evaluation.
Dogs in remission usually still have cancer; it is just undetectable for the time being. Treatment can buy your dog some time, but it rarely cures the disease and unfortunately most dogs with lymphoma will have a relapse at some point. When the cancer returns, it is more resistant to treatment, although a second remission can be achieved in some cases. Eventually, however, lymphoma is fatal.