Canine & Feline Lymphoma – What You Need to Know
You may be aware that like people, pets can too develop cancer.
But did you know that some types affect pets more commonly than others? Lymphoma is one of the most common types of cancer affecting our canine and feline companions.
Lymphoma is a disease that has personally affected my family and shaped my veterinary practice, as my dog Cardiff overcame Lymphoma twice and had a great quality of life despite having two surgeries and receiving ongoing chemotherapy treatment. Cardiff’s lymphoma led to us being featured in My Friend: Changing the Journey, a documentary about canine cancer created by the Canine Lymphoma Education Awareness and Research (CLEAR) Foundation. Although Cardiff is no longer with us, he didn’t succumb to cancer and his message of overcoming adversity still inspires others to this day.
What is Lymphoma?
Lymphoma is a malignant cancer affecting the white blood cells. Cancerous cells are those having abnormal DNA that lack a mechanism to turn off their own division. As a result, cancer cells divide in an out-of-control manner, cause damage at the sites of tumor growth, and can negatively affect other organs systems (digestive, immune, glandular, nervous, etc.).
Cancer can be divided into two subclasses, benign and malignant. Benign cancers are those that are less-likely to metastasize (spread to other body systems) and therefore have a better prognosis for resolution or management, but they still can be locally invasive and cause health concerns. Malignant cancers are more-likely to metastasize and generally have a worse prognosis for resolution or management.
Lymphoma, also known as lymphosarcoma, is a cancer of the lymphocytes, which are one type of white blood cell. White blood cells are immune system cells produced by the bone marrow, spleen, and other organ systems that play a crucial role in protecting the body from invading pathogens (bacteria, virus, fungus, etc.), controlling inflammation, managing stress, and facilitating a variety of other bodily functions.
The lymph nodes, gastrointestinal tract (stomach, small and large intestine, etc.), kidneys, liver, spleen, nervous system, skin, bone marrow, and other systems can be affected by lymphoma.
According to the World Health Organization (WHO), Lymphoma also has a five-tier staging system based on its degree of metastasis and invasiveness, including:
- Stage I:Restricted to a single lymph node.
- Stage II:Regional lymphadenopathy (enlargement of lymph nodes) restricted to one side of diaphragm. The diaphragm is a thin layer of muscle separating the chest and the abdominal cavities. Stage II means lymphoma can be found in the chest cavity or abdominal cavity, but not both.
- Stage III:Generalized lymphadenopathy (i.e. enlarged lymph nodes on both sides of the diaphragm)
- Stage IV:Hepatosplenomegaly (enlargement of the liver and spleen) with or without lymphadenopathy
- Stage V:Bone marrow, CNS (Central Nervous System), or involvement of other extranodal (non-lymph node) locations
Besides staging, Lymphoma is also grouped in two immunophenotypes, B-cell and T-cell. B-cell lymphoma generally has a better prognosis (“B is better”), while T-cell has a worse prognosis (“T is terrible”). Although being diagnosed with B or T-cell Lymphoma affects prognosis it does not determine the type of treatment prescribed for a particular patient.
According to the National Canine Cancer Foundation, Lymphoma makes up for around 7-24% of all canine cancers and 83% of all canine hematopoietic (blood cell) cancers.
PetMD reports that Lymphoma accounts for around 33% of all feline tumors and 90% of feline hematopoietic cancers and is the most common cause of feline hypercalcemia (elevated blood calcium).
What are the Causes of Lymphoma in cats and dogs?
There are no particular known causes of cancer, but there are correlating factors including:
Age – Cancers like Lymphoma generally occur in middle-aged and senior pets, but juvenile and young adults can also be affected.
Genetics – Some canine breeds are more-predisposed to Lymphoma, including the Airedale, Boxer, Bulldog (English, French, etc.), Bull Mastiff, Basset Hound, Saint Bernard, Scottish Terrier, and others. Breeds having a lower risk include the Dachshunds and Pomeranian. There’s less known about pure bred cats having a predisposition to develop Lymphoma as compared to their canine counterparts, but the Maine Coon is one breed that can be more-commonly affected by the disease. Mixed-breed dogs and cats are also known to develop to Lymphoma.
Lifestyle – Overweight and obese pets have elevated levels of inflammation in their bodies, which triggers cellular changes that can contribute to development of cancer.
Environment – Exposure to toxins such as pesticides (2,4-D herbicides applied to lawns, etc.), aflatoxins (from molds), heavy metals (arsenic, etc.), chemical-food preservatives (BHA, BHT, etc.), acrylamide (from cooking starches at 248F or greater), and others has been correlated to cancer.
Medications – Some immunosuppressive drugs (cyclosporine, azathioprine, etc.) have been associated with the development of Lymphoma.
Infectious organisms – Viral infections like Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) are associated with the development of lymphoma in cats.
What Symptoms Do Canines & Felines Show When Having Lymphoma?
Lymphoma causes a variety of clinical signs, some of which are also caused by other diseases, including:
Lymphadenopathy – As Lymphoma directly affects the white blood cells, the lymph nodes which help drain body parts can enlarge and feel firm, warm, or painful to the touch.
Lethargy – Lymphoma causes pets to have less energy for their day-to-day activities.
Hyperthermia – Elevated body temperature (hyperthermia) can be seen in pets having lymphoma. Normal body temperature is 100-102.5F (+/- 0.5).
Appetite changes – Anorexia (no appetite) or hyporexia (decreased appetite) are commonly in by pets suffering from Lymphoma.
Vomit or regurgitation – Since the digestive tract can be affected by Lymphoma, pets can exhibit vomiting (active abdominal contraction) or regurgitation (passive evacuation) to expel stomach contents from the stomach, up the esophagus, and out the mouth.
Bowel Movement Abnormalities – The small and/or large intestine can be affected by lymphoma and result in some combination of stool changes, including soft or liquid consistency, alternated bowel movement patterns, the presence of mucus and/or blood, flatulence (“farting”), etc.
How is Lymphoma Diagnosed in Cats and Dogs?
Since lymphoma has so many symptomatic commonalities with other diseases, it’s crucial that veterinarians combine a thorough medical history with a physical exam and a variety of diagnostic tools to get a full assessment of the degree to which a pet’s body is affected, including:
Blood testing – Chemistry (organ system function, protein, electrolyte, calcium, etc.), Complete Blood Count (CBC, to assess red and white blood cell and platelet levels), immunophenotype (B-Cell vs T-Cell Lymphoma), and others are tools that help determine overall health status and the patient’s ability to tolerate treatments like chemotherapy.
Urinalysis and culture – Assessment of urinary tract functioning and screening for abnormalities (reduced kidney function, infection, crystals, etc.) is crucial as the kidneys are an organ system serving to detoxify the body and clear chemotherapeutic drugs.
Fecal parasite analysis – Evaluation of feces for parasites is needed, as underlying parasitic infection can contribute to digestive tract signs (appetite and stool changes, etc.) that can be related to lymphoma and its treatment (chemotherapy, etc.).
Radiographs (x-rays) – X-ray imaging of the chest, abdomen, and other body parts gives a static (non-moving) viewpoint that is key in diagnosing lymphoma and monitoring a patient for remission or recurrence.
Ultrasound – Ultrasound is a moving imaging modality that commonly is used to assess body parts that aren’t as easily differentiated with radiographs, like the abdominal organs and lymph nodes.
MRI and CT – Both magnetic resonance imaging (MRI) and computed tomography (CT) are advanced imaging that permit deeper evaluation into areas of the body that can’t be thoroughly evaluated by radiographs and ultrasound, like the brain, spinal cord, nasal and oral passages, and body cavities. Both MRI and CT scan require a pet to be fully anesthetized under gas anesthesia, while for radiographs and ultrasound a patient is usually kept awake or mildly sedated.
What Kind of Treatments Are Used to Treat Lymphoma in Canines and Felines?
A variety of treatments are used for pets diagnosed with lymphoma. Which treatments are selected depends on the needs of the particular patient, the recommendations of the overseeing veterinarian, the age and quality of life of the pet, the owner’s ability to afford treatment, and other factors.
The goal of cancer treatment is to put the patient into remission, meaning that no detectable evidence of cancer cells can be found. Yet, even though a pet can be deemed in remission there’s still the potential for cancer to recur as sometimes cancer cells can hide in places in the body that elude our diagnostic tools or new cancer cells form when treatment is discontinued or ineffective.
Some of the most common treatments for Lymphoma include:
Chemotherapy – Chemotherapy uses chemicals that kill rapidly dividing cells, both cancerous and noncancerous. By administering different drugs in specific intervals over a series of months, chemotherapy aims to stop division of cancer cells by targeting different points in their replication.
One of the most common chemotherapy protocols is the University of Wisconsin-Madison Canine Lymphoma Protocol (CHOP), which stands for four drugs that are given intravenously (IV) or orally: Cyclophosphamide (Cytoxan), Hydroxyadaunorubucin (Doxorubicin), Oncovin (Vincristine), and Prednisone.
Cardiff received CHOP on an ongoing basis during the treatment of his two bouts of T-cell Lymphoma and had very few side effects despite receiving different combinations of drugs for three years post-diagnosis.
Immunotherapy – Relatively new to veterinary medicine is monoclonal antibody (MAb) treatment, which uses antibodies to stimulate the immune system to recognize and eliminate cancer cells. Antibodies are immune system proteins that are produced in response to exposure to an agent to which the body may or may not have previously been exposed, like infectious organisms (including viruses, bacteria, fungi, and others) or vaccinations.
MAb does not directly kill cancer cells like chemotherapy. Instead, MAb “targets a specific marker on the surface of the cell. Once this antibody binds it then signals the immune system to kill the cell or tells the cell to commit suicide” according to Cardiff’s veterinary oncologist, Dr. Avenelle Turner of Veterinary Cancer Group.
Cardiff tolerated MAB therapy very well, received it in conjunction with chemotherapy, and generally appeared to feel better and have fewer chemotherapy side effects.
Surgery – In veterinary medicine, the adage exists that “a chance to cut is a chance to cure.” When it comes down to it, if the option to perform surgery to remove cancer exists, then remission may be more readily achieved than using chemotherapy as the exclusive treatment.
With Lymphoma, chemotherapy is often the first line of treatment recommended over surgery since pets generally present with at least Stage II disease and multiple body systems can reap the benefits of treatment with chemotherapy. Yet, surgery can be used to remove a localized tumor or lymph node.
In both of Cardiff’s episodes of Lymphoma he did not show lymphadenopathy, but instead had a single tumor on a loop of small intestine that reduced the ability for food and fluid to properly pass. Surgery removed Cardiff’s diseased section of intestine, restored normal intestinal function, and allowed for other abdominal tissues to be biopsied to search for cancer or other abnormalities. After a 14-21 day healing process, Cardiff then started CHOP to help kill cancer cells (microscopic disease) that could become tumors (macroscopic disease).
Radiation – When needed, radiation can be used to kill cancer cells and shrink tissue. Pets undergoing radiation treatment need to be fully anesthetized under gas anesthesia to receive treatment, yet they are often only anesthetized for less than 30 minutes and readily recover to resume their day-to-day lives.
Complementary and Alternative Medicine (CAM) – CAM can be pursued to complement chemotherapy and surgery or can be used when an owner elects to not have a pet undergo such conventional treatment options.
Since chemotherapy kills both normal and cancerous cells the bone marrow and digestive tract are sites commonly enduring side effects. The use of probiotics (beneficial bacteria) and other agents that sooth the stomach and small and large intestines (ginger, licorice root and allow leaf extracts, glutamine, calcium aluminosilicate, etc.) can help maintain digestive function and minimize side effects. The Honest Kitchen’s Pro Bloom instant goat’s milk is a great source of probiotics.
Antioxidants can help to counteract some of the oxidation (tissue damage) caused by cancer and other diseases. Yet, antioxidants should not be given on the day of chemotherapy or radiation to help minimize inadvertent reduction of treatment efficacy.
Fish oil based omega fatty acids have a natural anti-inflammatory effect that can promote the health of the immune system, skin, joints, nervous system, etc. along with helping to battle cachexia (cancer-related weight loss).
Herbs like turmeric (Honest Kitchen’s Beef Bone Broth is a good source), silymarin (milk thistle), mushrooms (Shiitake, Maitake, etc.), Yunnan Biayao, etc., can have the effect of reducing inflammation, promoting blood flow, improving organ system function, stimulating white blood cell production, and more.
My patients eating whole-food, human-grade meals (such as The Honest Kitchen’s low carb recipes Marvel, Embark and Love for dogs and Grace and Prowl for cats) and treats generally are healthier, have improved digestive and immune system function, and tend to show fewer side effects from chemotherapy, radiation, and anesthesia.
Acupuncture, acupressure massage, Cyanocobalamin (Vitamin B12) aquapuncture injections, and other modalities can help manage chemotherapy side effects and generally improve a pet’s comfort and well-being.
To ensure that pets having cancer undergo the most thorough evaluation, I recommend owners seek consultation with a veterinary oncologist. Although general practice veterinarians can diagnose and treat cancer, I feel it’s best to have the primary veterinarian be one who works exclusively in the realm of cancer treatment and is aware of potentially beneficial clinical trials. Your general practice veterinarian can refer you to a veterinary oncologist or one can be found via the American College of Veterinary Internal Medicine (ACVIM).
Additionally, when seeking CAM treatments work with a veterinarian experienced in that realm like a member of the American Holistic Veterinary Medical Association (AHVMA) or a certified veterinary acupuncturist (CVA).