WHY IS CANINE LYMPHOMA DR. ALICE’S FAVORITE CANCER?
By Alice Villalobos, DVM, FNAP 2018
Director, Pawspice and Animal Oncology Consultation Service
Lymphoma, cancer of the lymph glands (nodes), is my favorite cancer because most dogs that develop nodal lymphoma feel well despite their enlarged lymph nodes. There are more severe forms of lymphoma, which attack internal organs and the intestinal tract. Occasionally, it can appear in the skin. It surprises pet carers to learn that nodal lymphoma may kill their beloved dogs, who seems so well, within three weeks to three months if left untreated. I highly recommend that all canine lymphoma patients be treated with combination chemotherapy using the Modified Wisconsin Protocol.
This protocol may include L-asparaginase and always includes IV Adriamycin given in a split dose sequence and IV vincristine, and oral Cytoxan and Leukeran. Remember all patients receiving chemotherapy for any type of cancer require complete blood counts (CBC’s) in order to monitor the white blood cells, platelets and red blood cells. We run the CBC before each treatment. If the WBC is too low (<3,500) and if the Neutrophil count is below 1,800, antibiotics will be needed. We adjust the dose of your dog’s chemotherapy to be reduced or postponed. The doses and sequence of Chemotherapy protocols for Lymphoma must be adapted for individual dogs depending on their body score, the severity of the lymphoma, the status of organ function and other pre-existing disease conditions. If the dog has liver or kidney disease, enlarged organs or if the lymphoma involves the liver, caution is the key during the initial induction phase. At times the protocol must be adjusted to administer medications over a more prolonged period with IV fluids and supportive care in the hospital. At time we may teach you how to administer subcutaneous fluids and supportive care at home, especially if we need to work within a budget.
The first week of treatment, known as Induction, is often a happy week as most lymphoma dogs feel great being on prednisone at 30 mg/M2 PO q24h for 7 days. This shrinks the nodes and stimulates the appetite. If only prednisone is given as treatment for lymphoma, you should be advised that this is only one bullet in the six-shooter for therapy and your dog will not survive any longer than the initial prognosis of 3 weeks to 3 months. Some oncologists feel that the use of Prednisone for more than two weeks before starting chemotherapy predisposes lymphoma dogs to develop resistance to future therapy.
The induction on day one is with Vincristine, which is given I.V. at 0.7 mg/m2. L-asparginase may also be given on day one at 10,000 iu/m2 I.M. after pretreatment with Benadryl and dexamethasone. Prednisone initially given at 30mg/m2 per day and is reduced to 20 mg/M2 per day for the second week and then reduced again to 10 mg/m2 daily for the third week and then given every other day for a week or two and then stopped. We use the prednisone again when Cytoxan is given orally in order to encourage water intake and discourage Cytoxan-related hemorrhagic cystitis. Cytoxan is given orally at 200 mg/m2 over two days on week two. Adriamycin, AKA, “Red Death,” due to its red color, is a mold derived drug that we prefer to give in a “split dose” fashion to medium and large larger dogs on weeks 3 and 4 as an I.V. infusion at 20mg/m2. This technique avoids the known cardiac toxicity associated with this drug. If your dog is overweight, we always use the true lean body weight for the dose calculations. If your dog is sick, frail, anemic or thin, a dose adjustment will be made in the work orders. If your dog has heart disease, Adriamycin may be substituted with Mitoxantrone (AKA Blue Thunder for its coor). Adriamycin is known to cause cardiomyopathy in humans and dogs. Breeds such as Doberman Pinchers that are susceptible to cardiomyopathy are at greater risk if Adriamycin is used at the traditional dose.
Vincristine is given IV after a CBC is evaluated on the week four visit and Cytoxan with Prednisone is given on week five and the Adriamycin again on week six. I have the client return on week eight for vincristine and a maintenance consult.
I prefer to keep my canine lymphoma patients on permanent maintenance protocols. We prefer monthly recheck visits for a physical exam and CBC and vincristine. Following each visit for vincristine, we rotate oral Cytoxan at the above dose and Chlorambucil at 1.4 mg/kg PO divided over two days as our maintenance protocol for lymphoma dogs.
Recurrent and resistant lymphomas are treated with reinduction of the Wisconsin protocol or other rescue protocols. Tanovea is a new more targeted lymphoma drug specifically introduced to treat dogs that come out of remission or dogs that are resistant to standard drugs. It is given as an IV every 3 weeks. It may be used for induction but we prefer to reserve Tanovea it for rescue. Vaccines for lymphoma have been studied for decades. Recently, there are a few that have become available; however, we need to evaluate their efficacy in clinical practice.
There are many ways to help dogs with lymphoma live a long and happy quality life.
We routinely anticipate the typical adverse events or side effects related to chemotherapy. We send home a “Cancer Care Package” that treats nausea, vomiting and fever. We send a thermometer to detect fevers and instruct you to use Ondansetron for nausea, anorexia and vomiting. We send Flagyl for diarrhea and an antibiotic in the event a fever is detected. The most important consideration is quality of life and to avoid distressing side effects. Our Pawspice Team supports the human-animal bond, which is why you, our valued careers, come with your lymphoma dog for consultation in the first place.