Introduction
Lymphoma is a type of cancer that originates in the lymphocytes, which are white blood cells that are part of the immune system. In dogs, lymphoma typically occurs in the lymph nodes, spleen, liver, and bone marrow, and occasionally in other organs (Source).
The most common symptoms of lymphoma in dogs include enlarged lymph nodes, lethargy, decreased appetite, weight loss, increased thirst and urination, vomiting, and diarrhea. Dogs with lymphoma involving organs like the liver or kidneys may show symptoms like abdominal swelling, difficulty breathing, pale gums, bruising, and yellowing of the skin and eyes (Source).
The prognosis for dogs with lymphoma depends on the stage and subtype of the cancer. With treatment, the average survival time is 6-12 months. Some subtypes, like the gastrointestinal form, carry a worse prognosis than others (Source). Early detection and treatment is key for improving outcomes.
Stages of Lymphoma
Lymphoma typically progresses through 5 stages (WSU Veterinary Teaching Hospital):
Stage I – only one lymph node is enlarged
Stage II – multiple lymph nodes are enlarged, either in front of the diaphragm or behind it (front or back half of the body)
Stage III – multiple lymph nodes are enlarged on both sides of the diaphragm (both front and back of the body)
Stage IV – involvement of liver and/or spleen, with or without lymph node involvement
Stage V – involvement of the bone marrow and/or other organs like the kidneys, lungs, or central nervous system
As lymphoma progresses through these stages, symptoms become more severe. In early stages, dogs may not show any symptoms at all. By late stage lymphoma (stages III-V), dogs display symptoms like lethargy, decreased appetite, weight loss, swelling of lymph nodes, vomiting, and diarrhea (Swift Referrals).
Diagnosis
Lymphoma is diagnosed through a combination of a physical exam, imaging tests, and a lymph node biopsy. During a physical exam, the veterinarian will palpate the lymph nodes and look for enlargement, which is one of the most common signs of lymphoma in dogs. They may feel enlarged lymph nodes in the dog’s neck, groin, under the jaw, or behind the knees. Some lymph nodes like those under the jaw may normally be enlarged, so comparing left and right sides is important. Along with an enlarged lymph node, the veterinarian will look for other signs like lack of appetite, lethargy, and weight loss.
Imaging tests like x-rays, ultrasound, or CT scans can help identify affected lymph nodes and look for signs of spread to other organs. X-rays are useful for looking at the chest and abdomen for enlarged lymph nodes or masses. Ultrasound uses sound waves to create images of the lymph nodes and other organs. It allows the veterinarian to see size, shape, and internal architecture of organs and nodes. CT scans provide even more detailed 3D images. These tests help identify the best locations to obtain a biopsy.
The most definitive way to diagnose lymphoma is to examine cells from an affected lymph node under a microscope. This is done by a needle aspiration biopsy where cells are withdrawn using a thin needle inserted into an enlarged node. In some cases, a surgical biopsy may be done to remove an entire lymph node for analysis. Examining the cells under a microscope allows the veterinarian to determine if they are cancerous lymphocytes and definitively diagnose lymphoma (source).
Treatment
The most common and effective treatment for lymphoma in dogs is chemotherapy. There are many different chemotherapy drugs and protocols that veterinary oncologists may use, often combining multiple drugs like cyclophosphamide, doxorubicin, vincristine, and prednisone (Canine Lymphoma Research). Chemotherapy can lead to remission lasting months to years in many dogs with lymphoma. The goals of chemotherapy are to kill cancerous lymphocytes, achieve remission, improve quality of life, and extend survival time (Lymphoma in Dogs – VCA Animal Hospitals).
Radiation therapy may be used in addition to chemotherapy to treat localized lymphoma or for palliative care. Immunotherapy drugs are also sometimes used to stimulate the immune system to fight lymphoma.
Progression
If left untreated, lymphoma tends to be an aggressive disease that can spread throughout the body. The cancerous lymphocytes can proliferate rapidly and invade different organs and tissues.
Lymphoma usually starts in one area of the body, often a lymph node. From there, it can spread to other lymph nodes and lymph tissues, such as the spleen, liver, and bone marrow. As it progresses, lymphoma may infiltrate the gastrointestinal tract, respiratory system, skin, kidneys, and central nervous system.
The speed at which lymphoma spreads depends on the type and stage. For example, intermediate and high-grade lymphomas tend to progress more quickly than low-grade lymphomas. According to the Veterinary Cancer Society, the approximate doubling time for lymphoma cells ranges from 7-20 days for intermediate grade lymphomas to 28-40+ days for low grade lymphomas (Source).
As lymphoma advances untreated, it impairs the normal functioning of organs by crowding out healthy cells. This can lead to organ dysfunction and failure, which is often what ultimately proves fatal if the cancer remains unchecked.
Organ Failure
One of the eventual causes of death for dogs with lymphoma can be organ failure. As the cancer spreads through the body, it can damage major organs like the liver, kidneys, and lungs. According to the Merck Veterinary Manual, lymphoma is known to frequently spread to organs like the liver, spleen, bone marrow and kidneys https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/malignant-lymphoma-in-dogs. The lymph nodes around these organs become enlarged with cancerous lymphocytes. Eventually the organs themselves can become impaired. Liver enlargement is very common in dogs with lymphoma according to VCA Hospitals https://vcahospitals.com/know-your-pet/lymphoma-in-dogs.
As the major organs fail, they are no longer able to perform their essential functions in the body. Kidney failure leads to buildup of toxins and electrolyte imbalances. Liver failure causes problems with blood clotting and metabolism. Lung impairment results in oxygen deprivation. Organ failure is often the ultimate cause of death in dogs with lymphoma if left untreated.
Bone Marrow Suppression
One of the most common side effects of chemotherapy is bone marrow suppression, which can lead to low blood cell counts [1]. The bone marrow is responsible for producing red blood cells, white blood cells, and platelets. When the bone marrow is suppressed by chemotherapy, it cannot produce enough of these cells.
A low red blood cell count (anemia) causes fatigue, weakness, and poor oxygen delivery. A low white blood cell count (neutropenia) increases the risk of infections. A low platelet count (thrombocytopenia) can lead to easy bruising and bleeding. These complications can become life-threatening if the counts become too low.
Veterinarians will monitor blood cell counts closely during chemotherapy. Medications called growth factors can sometimes be used to help stimulate the bone marrow. Transfusions of red blood cells or platelets may also be given if counts drop to dangerous levels. Supportive care with fluids, antibiotics, and anti-nausea medication helps manage these side effects.
Nutritional Complications
Lymphoma and its treatments can lead to several nutritional complications in dogs, including anorexia, nausea, and weight loss. Chemotherapy drugs in particular are known to suppress appetite and cause gastrointestinal upset.
Anorexia, or loss of appetite, is common in dogs with lymphoma. The cancer itself can release chemicals that impact appetite centers in the brain. Nausea is also frequently seen, due to direct effects of lymphoma on the digestive tract as well as side effects of chemotherapy. These issues can lead to weight loss and muscle wasting, further impacting strength and quality of life.
According to the Veterinary Cancer Society, “Cachexia (severe muscle wasting) is a common paraneoplastic syndrome in dogs with lymphoma.” This cachexia is distinct from simple starvation and indicates complex metabolic changes related to the cancer [1].
To manage nutritional complications, vets may prescribe anti-nausea medication and appetite stimulants. Highly palatable prescription diets, such as Hill’s Prescription Diet n/d, are commonly recommended for lymphoma patients. These diets are very digestible and energy-dense to counteract anorexia and weight loss. Adding enrichment like broths, gravies, or meat drippings can also stimulate appetite.
Nutritional support is an important part of caring for a dog with lymphoma. Managing anorexia, nausea, and weight loss can help dogs maintain strength, energy levels, and quality of life during treatment.
Euthanasia
There comes a point for some owners when euthanasia seems like the most humane option for their dog with lymphoma. Once treatment options have been exhausted, dogs often deteriorate rapidly. Owners may choose euthanasia to prevent their pet from suffering once the lymphoma has progressed to an advanced stage. Reasons lymphoma may lead owners to euthanize dogs for humane reasons include:
Extreme weight loss and muscle wasting – As the cancer spreads, dogs become extremely emaciated. They lose their appetite and have difficulty eating due to nausea, mouth sores, and gastrointestinal issues. Owners may opt for euthanasia when their pet becomes extremely underweight and frail.
Difficulty breathing – Lymphoma can spread to the lungs, causing fluid buildup, pneumonia, and breathing issues. Dogs struggling for air are clearly suffering. Euthanasia may be chosen to end respiratory distress.
Bleeding problems – Some lymphomas lead to dangerously low platelet counts, causing spontaneous bleeding. Internal hemorrhaging is extremely painful. Owners may decide to euthanize when bleeding becomes severe.
Loss of mobility – Lymphoma can infiltrate bones and joints. Dogs may lose the ability to stand or walk. Euthanasia may be elected when dogs can no longer get up on their own.
Uncontrolled pain – Despite pain medication, some dogs reach a point where they are in obvious discomfort. Euthanasia ends pain and suffering in these cases.
No quality of life – When dogs are extremely weak, in pain, and unable to eat or move, owners may feel euthanasia is the most compassionate choice. Allowing a pet to die naturally often means prolonged suffering.
As cited from https://cloud9vets.co.uk/dog-lymphoma-when-to-euthanise-and-what-your-dog-will-feel/, owners should focus on their pet’s quality of life and opt for euthanasia before the cancer causes intense pain and distress. It is a heartbreaking decision, but one made out of love and a desire to alleviate suffering.
Takeaways
The key takeaways for owners of dogs with lymphoma are:
- Catching lymphoma early and starting treatment quickly can significantly improve prognosis.
- Chemotherapy is often used to treat canine lymphoma and can extend a dog’s life by months to years.
- Providing adequate nutrition, hydration, pain management, and loving care can keep your dog comfortable.
- Monitor your dog closely and watch for signs of disease progression like breathing issues.
- Discuss end-of-life care options with your vet when your dog’s quality of life declines.
- Euthanasia can be the most humane option when lymphoma has progressed significantly.
- Focus on providing your dog the best quality of life for the time you have left together.