Canine lymphoma

In our continuing look at canine cancer, this month, letís look at one of the most common ó lymphoma. This type of cancer represents about 24 percent of all new cancers seen in dogs at the Flint Cancer Center at Colorado State University. Lymphomas vary greatly in how they act. Some progress rapidly and are acutely life-threatening without treatment, while others progress slowly and are managed as a chronic disease. Lymphomas may affect any organ in the body, but most commonly originate in lymph nodes, before spreading to other organs such as the spleen, liver and bone marrow.Canine lymphomas are similar in many ways to the non-Hodgkin’s lymphomas (NHL), which occur in humans. In 2019, NHL was diagnosed in about 77,000 people in the United States and claimed about 20,000 lives, making it the seventh most common cancer overall, and the sixth most common cause of cancer-related deaths; and the incidence is still climbing.The term ìlymphomaî describes a group of cancers in dogs that are derived from white blood cells called†lymphocytes. This cancer is most common in the lymph nodes, spleen and bone marrow. By far, the most common type of lymphoma in the dog is one in which the cancer is initially apparent in†lymph nodes.As with so many cancers, the cause of lymphoma in dogs is not known, although several possible causes such as viruses, bacteria, chemical exposure and physical factors have been studied. The most common initial symptom of lymphoma in dogs is firm, enlarged, non-painful lymph nodes. The nodes that are most easy to feel are just under the jaw and neck, and ones just behind the knee. A lymph node affected by lymphoma will feel like a hard, rubbery lump under your dogís skin. Other†common symptoms include loss of appetite, lethargy, weight loss, swelling of the face or legs (edema), and occasionally increased thirst and urination.†Swelling of a part of the body typically occurs when one of these swollen nodes blocks circulation.There are other types that can be confusing, like cutaneous lymphoma that can look like skin disease or infection. Another common one we often see is gastrointestinal lymphoma. Here the cancer grows in the wall of the intestines so you would see vomiting, diarrhea and weight loss ñ- signs that look like so many other problems.The best way to diagnose lymphoma is after a physical exam; seeing these typical swellings, your veterinarian would perform a†biopsy. This is a minor surgical procedure to remove a piece of lymph node or other organ affected by cancer. The lab will recommend you ìstageî the cancer. This helps to determine how far the cancer has spread and gives you a prognosis. Treatment decisions are often made based on this biopsy and staging.The most effective therapy for most types of canine lymphoma is chemotherapy. But in some cases, surgery may also be recommended. While radiation is part of the treatment of lymphoma in humans, it is so hard to do in dogs because they require general anesthesia for each therapy. This adds greatly to both the risk and the cost.There are numerous chemotherapy treatment protocols for dogs, but the protocol used as a ìgold standardî for the treatment of canine lymphoma is a 25-week protocol called†UW-25. It is based on a protocol called†CHOP†that is commonly used to treat lymphoma in humans.Most dogs tolerate chemotherapy pretty well, frankly much better than humans typically do. Although some dogs do get sick from chemotherapy, serious side effects are not common.Unlike people, dogs usually do not lose their hair when treated with chemotherapy. The exceptions to this rule are poodles, Old English sheepdogs and some terriers. Hair should come back when chemo is stopped.Your dogís prognosis will be determined by what type of lymphoma he or she has and what type of chemotherapy is used to treat it.†The median length of survival for dogs with lymphoma treated with UW-25 chemotherapy is between 9-13 months.†(The term ìmedianî implies that 50 percent of dogs will survive beyond this time point and 50 percent of treated dogs will die before this time point.) Various other factors, such as the type of lymphoma your dog has or its stage of disease, may affect your dogís overall prognosis.The key is to get an early diagnosis. This means letting your veterinarian look at ANY lump or bump and make a decision about a biopsy. Then, you will need an expert team of veterinarians that specialize in oncology to make decisions about surgery, second phases of chemo and perhaps new treatments that might work in your dogís case.The Flint Cancer Center at the Veterinary School at CSU has world-class experts who can guide you through this. If you do get a cancer diagnosis, remember it is often treatable.