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Lymphoma in the Dog
Lymphoma is primarily a cancerous condition of the lymph glands in the dog.
It can also affect other organs such as the liver and spleen and occasionally we see forms of lymphoma apparently only affecting
a single site such as the skin. As a general rule lymphoma affects anatomically distinct sites throughout the body. Therefore
treatment must likewise treat the whole body.
What is Lymphoma?
Lymphoma is a cancer of the lymphocytes, or white blood cells. There are multiple different types of lymphoma in the dog,
just as there are in humans, though at the moment this is really a concept that is only just reaching the wider veterinary
consciousness. The different types of lymphoma arise from malignant transformation of different types of lymphocytes or as
a consequence of different specific DNA aberrations acquired during the life of the individual patient. Most lymphoma types
respond favourably to the administration of chemotherapy. There are some that do not and it is important to attempt to identify
these cases as other treatments may be indicated.
In dogs, the life expectancy with most types of lymphoma is limited to only a few months. With chemotherapy protocols, this
is increased to an average of 6½ to 12 months depending on the treatment plan.
Evaluation
A diagnosis of lymphoma is usually made on examination of a pathological specimen. This might be a fine needle aspirate biopsy
of an enlarged lymph node or other structure or it may be a histopathological examination of a bigger biopsy specimen. At
the current time, most diagnostic evaluations stop once the diagnosis of lymphoma has been made. As alluded to above, this
is not always ideal. Further evaluations can be performed including immunocytochemistry and cytomorphological and histomorphological
assessments. Classification of canine lymphoma into the different subtypes will allow us to provide more specific treatment
and to provide more precise estimates of prognosis.
At the moment only a few of the more common subtypes have been fully characterised; as time passes and more experience is
gained this will improve. Some alternative, novel therapies are likely to arise for the less common disease presentations
and improved outcomes will be seen in the more common subtypes.
Other evaluations are important to understand the general health of the patient before decisions about chemotherapy are taken.
These include blood tests and possibly x-rays and ultrasound evaluations. Some types of lymphoma are associated with high
blood calcium concentrations, hypercalcaemia. It is important for the well-being of the patient that complications like this
are identified and managed appropriately.
Treatment Options
There are countless chemotherapy treatment plans (or protocols) that have been described for the management of canine lymphoma.
The principal candidates are described as multidrug chemotherapy protocols. They incorporate the three drugs Cyclophosphamide,
Vincristine (Oncovin) and Prednisolone, usually called the COP protocol, or the same three plus a drug called doxorubicin
(Hydroxydaunorubicin) usually called the CHOP protocol. The COP protocols have a reduced chance of inducing unwanted side
effects but carry a reduced probability of inducing a complete remission. The average life expectancy on this treatment is
approximately 6½ months. The CHOP protocols achieve complete remission in a higher percentage of cases and the average
life expectancy is improved as a consequence to approximately 11½ months but the risk of unwanted side effects is that
little bit greater.
The decision about which treatment plan to choose should be made in conjunction with your veterinary surgeon, whether they
are your local vet or your oncology specialist. This is not a one-size-fits-all situation. Some veterinary practices will
very sensibly only offer a single lymphoma protocol. The rationale here is that they see a reduced number of cases compared
to a veterinary oncologist; therefore it is important for optimal familiarity with the disease in question and the possible
range of manifestations of tumour and treatment response that every member of staff in the practice is used to using the same
treatment plan, otherwise things start to get very confusing and chemotherapy is not a thing to be confused with. Other factors
influence treatment choice such as accessibility of a specialist centre, cost of therapy, duration of therapy and of course
the patient’s own response to the drugs once they have been administered.
Chemotherapy induced side effects are usually minor if indeed they are noted at all. Nevertheless it is critical that the
risk of these effects is addressed and discussed openly prior to the onset of therapy. In many cases the improvement in the
patient’s condition substantially outweighs the minor impact of the treatment related side effects leading to an overall
improvement in general health despite chemotherapy.
Relapse
Lymphoma goes into complete remission in 70-85% of cases using standard chemotherapy protocols. The duration of this remission
is variable; a few cases may survive for years but usually patients will survive somewhere between 2 and 6 months. On relapse
of the disease, it is often appropriate to consider alternative therapy to attempt to regain control over the tumour. There
is a very strong association between long term survival and whether or not patients regain complete remission of their disease.
Sometimes it is appropriate to repeat treatment with the “induction” protocol which allowed them to achieve complete
remission in the first place. In other cases it is more appropriate to employ a new “rescue” protocol. “Chemotherapy
rescue” may be something that requires referral to a specialist centre.
Quality of Life
It is tremendously important to emphasise that patients undergoing chemotherapy (or any other cancer therapy for that matter)
do so because their team of carers, the primary veterinary surgeon, the veterinary oncologist and the family at home, all
feel that the treatment is improving quality of life at all times. Chemotherapy and cancer rightly carry a certain stigma.
We take great pains to ensure that any potential side effects are discussed fully prior to embarking on a course of cancer
therapy. This way our owners make informed decisions about the treatment choices they have for their pets. The aim of our
cancer therapy is to promote a good quality of life first and foremost and life expectancy second.
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