Lymphoma is a frequently diagnosed cancer in dogs. It is a cancer of lymphocytes, which are a type of white blood cell normally tasked with fighting infections. There are many different forms of lymphoma in dogs, with the most common type (multicentric lymphoma) bearing close resemblance to Non-Hodgkin’s lymphoma in people.
The recommended treatment plan for multicentric lymphoma in dogs is a 6-month course of a multi-drug injectable chemotherapy protocol. This treatment plan is extremely effective at achieving remission, which is a term used to describe when a patient no longer shows any visible, detectable evidence of their disease.
Remission rates are greater than 80%, and survival times can be extended well beyond what would be expected without any treatment.
Remission, unfortunately, does not equate with a cure. Cure would imply that treatment resulted in complete eradication of all of the cancer cells from the dog’s body. Remission indicates the disease is no longer detectable, but is still present.
Ninety-five percent of dogs treated for lymphoma will experience disease relapse (i.e., “come out of remission”). The timing of when this happens is variable.
Relapse typically manifests with the same clinical signs as were shown during the initial diagnosis. For example, if the initial signs of disease were enlarged peripheral lymph nodes that reduced to normal size during treatment, at relapse the lymph nodes would enlarge again.
If the patient was initially administered the multi-drug protocol mentioned above, this is usually considered the most successful plan in re-inducing remission once relapse occurs. The main exception to this recommendation would be a dog who experienced relapse in the midst of, or within a few short weeks of completing, the protocol. In those patients, rescue protocols are more appropriate and effective choices.
There are a many different rescue protocols for canine lymphoma. Amongst veterinary oncologists, owners are surprised to hear there is no one universally agreed upon “next best” way to proceed. Rescue protocols vary in terms of success of inducing remission, expected duration of remission, number of trips to the oncologist for treatment, chance of side effect, and cost.
Many owners are willing to treat their dog with lymphoma with chemotherapy once. Far fewer will embark on additional treatment once relapse is detected. The variables listed above also influence owner’s decisions about how they would next like to proceed.
For some, cost of treatment is not an issue, and efficacy is their primary goal. For others, the price tag associated with the drugs limits what they are able to pursue.
Even when finances do not play a role, aspects of treatment related to the emotional and time commitments required for appointments influence what an owner is, and is not, capable of.
When dogs with lymphoma experience relapse of disease it is a devastating reminder to owners of their pets’ vulnerability. It means their dog will not be a part of the 5% who are cured. It means revisiting the idea of continued chemotherapy. It means additional obligations they may be unprepared for. And it means genuinely facing their pet’s mortality, which is something they may have deeply buried during the time their dog was in remission.
From a clinician’s perspective, relapse evokes a similar set of emotions. These are owners and animals with which I’ve journeyed through diagnosis and six months of treatment. I’ve learned much about their lives, their families, and, of course, their dogs. When a dog comes out of remission, despite knowing the odds were never stacked in my favor, it still feels like a professional failure.
Once lymphoma resurfaces, it’s a harsh reminder that it was always there, lurking beneath the surface of a pet that otherwise behaves exactly the same as a healthy pet. Though I try to stress that relapse is simply an outward manifestation of the dog’s cancer and that there are many options available to re-induce remission, I remind owners that just because we can do something doesn’t mean we have to do anything.
Relapsed cases remind me that the palliative nature of veterinary oncology is a double-edged sword. I afford pets that have cancer with the chance to live longer and happier lives, which fulfills my goals to be an advocate for animals. But I cannot cure them because I must administer doses of drugs at levels designed to maintain a good quality of life during treatment rather than invoking a cure.
This is a bittersweet compromise I make as a veterinarian, who more than anything, must always ensure that I first do no harm.
Dr. Joanne Intile