When I (Perry Jameson) was being trained as a veterinary internist at the University of Georgia from 1992 to 1995, I learned how to diagnose and treat all medical diseases of dogs and cats.
Now, a veterinary internist deals primarily with gastrointestinal, pulmonary, hormonal and blood disorders. Twenty-five years ago, however, we were trained to deal with anything medical.
My day might consist of stopping a dog from seizing then figuring out why she was seizing in the first place. Next, I would walk into an exam room to find a cat in heart failure. Here, too, I would begin therapy and figure out the cause. The following patient would be there to receive chemotherapy for cancer. In between, I was treating dogs and cats for vomiting, diarrhea, Cushing’s disease, Addison’s disease and hundreds of other conditions. There were days I felt like a literal jack-of-all-trades, master of none.
In 1996, Dr. Katherine Taylor moved to the Charleston area and needed a job. Dr. Taylor had just finished her oncology residency at Auburn University. She was a veterinary oncologist, which focuses primarily on the diagnosis and treatment of cancer in pets. Over the past 14 years the need for our oncology service has increased to two locations.
Lymphoma is one of the more common forms of cancer that the oncology team treats. This is a cancer of lymphocytes, a type of white blood cell. They live in lymph nodes but also in most every tissue in the body while circulating through the bloodstream.
Most pet parents notice swollen lymph nodes as the first symptom. However, since they are everywhere, symptoms of the cancer can vary based on which organs are affected.
When I was diagnosing this disease, we would aspirate samples from a lymph node and submit these spread out onto a glass slide for a pathologist to review under the microscope. If nondiagnostic, we would have to surgically remove the lymph node (or surgically biopsy whatever organ was involved) and submit this to a pathologist.
I recently sat down with Dr. Taylor to see what had changed over the past 14 years with how lymphoma is diagnosed and treated in dogs.
First, she pointed to safer handling of the drugs for her and our staff. When she first started, she would draw the drugs into a syringe from a vial in front of her face with the only protection being exam gloves. Now all medications are removed from the original vial under a special fume hood that is constantly venting air away. This way, if any microscopic particles are released, they do not get on the nurse. Also a closed system between the syringe and vial is used to decrease the chance of any microscopic particle being released. The nurses wear face shields, gowns and special gloves to further decrease the risk of any exposure.
When I see how they handle the drugs now compared to how I once did, I can only imagine the amount of chemotherapy I inadvertently exposed myself to.
Dr. Taylor says the biggest improvement in our ability to diagnose lymphoma is the addition of the tests PARR (PCR for antigen receptor rearrangements) and flow cytometry. These two tests look for genetic or cell-surface changes that help diagnose disease. Their addition has practically eliminated the need to ever get a biopsy.
Not only have they improved our ability to diagnose lymphoma with noninvasive testing, but they also have improved our ability to differentiate the types. There are two primary types of lymphocytes, B and T cell. The ability to differentiate the form improves Dr. Taylor’s ability to provide a more accurate prognosis and fine-tune her therapy.
She could not help but remember an older golden retriever she diagnosed with lymphoma prior to the advent of these tests. He was started on the standard regimen of aggressive chemotherapy but did not respond well. Finally, she felt she was causing more harm than good, so she stopped the aggressive medications and switched to an oral, less- aggressive chemotherapy.
Within a week, he was feeling great and in complete remission that lasted for several years. In hindsight, Dr. Taylor feels if these new tests had been available, she would have known to start with this milder medication from the beginning.
When asked if the therapeutic options have changed, she says, unfortunately, no. The drugs available have remained basically unchanged. The only major advance is a new drug that is used to re-induce remission when the standard drugs fail.
Overall, lymphoma remains a cancer for which we can get most dogs into a prolonged remission. Depending on the form and location. remissions can be anywhere from 6 to 24 months. Historically, the only way to know was to treat and see how they responded. Now, the PARR and flow cytometry help provide a prognosis prior to therapy.
Dogs tolerate chemotherapy well, certainly better than humans. Dr. Taylor stressed to me that dogs are not treated as aggressively as humans. Our goal is to prolong their life without side effects. Less than 10 percent of dogs have serious side effects requiring hospitalization. Around 20 percent have mild, transient side effects (vomiting, diarrhea, anorexia) for a day, then are back to normal.
Lymphoma is still almost always a fatal disease, but with appropriate therapy, dogs can go into a prolonged remission with few, if any, side effects.