Canine Lymphoma - Dick White Referrals

INTERNAL MEDICINE
Owner Information Sheet
Canine Lymphoma
Consultants: Rob Foale BSc BVetMed DSAM DECVIM-CA MRCVS, European Specialist in Veterinary Internal Medicine
Simon Tappin MA VetMB Cert SAM DECVIM-CA MRCVS, European Specialist in Veterinary Internal Medicine
Jon Wray BVSc DSAM Cert VC MRCVS, RCVS-Recognised Specialist in Small Animal Medicine (IntMed)
Lymphoma is a cancer of the lymphoid tissue within the body, a
complex system of immunological tissue which helps fight
infection, control inflammation and acts as a disease
„surveillance system‟ for the body. Lymphoma is the
commonest type of cancer that we see affecting the lymphoid
system dogs and is one of the commonest types of tumour
encountered by veterinary medical specialists (though its
incidence in the whole canine population is low). Many dogs
with lymphoma are young to middle aged and it is a common
misconception that only older dogs get cancer.
What causes lymphoma
Like most cancers, there is no single cause of lymphoma and
trying to find a 'culprit' event or illness that caused the tumour to
develop is futile. Most cancers arise through a complex
interaction of various factors involved with cell growth and
multiplication which usually follows an orderly progression
aided by several 'fail-safe' mechanisms. Whilst genetics,
environment, diet and prior disease exposure can all influence
the relative risk of developing cancer, it is ultimately a series of
predispositions, failure of these protective mechanisms and
coincidental factors being present simultaneously that leads to
a cell becoming cancerous and multiplying out of the body's
control. Thus claims that cancers are caused by 'modern diets',
vaccination, drug therapy, pesticides etc are really pretty naïve
statements that miss the point; large scale epidemiological
studies in people may highlight risk factors that can increase
ones risk of developing cancer (and these often appear as
scare stories in the news or on the internet) all show with very
few exceptions that no one factor is involved. Rest assured you
will have done nothing wrong to increase your pet's risk of
developing lymphoma.
What are the effects of lymphoma
Just like dogs, lymphoma comes in many shapes, sizes and
forms. The most common type of lymphoma that we see in
dogs is one called 'multicentric lymphoma', which affects one or
more of the various lymph nodes around the body. These are
very small bean-sized glands which act as surveillance points
for the immune system. Some are external and can be palpated
(felt) if you know what to feel for but others are inside the body
cavities and enlargement of these can only be detected with x-
rays, ultrasound or MRI. These swellings are usually not painful
and many dogs with multicentric lymphoma are initially not
particularly unwell.
LYMPHOMA CELLS
Other forms of lymphoma may affect the gut (gastrointestinal
lymphoma), kidneys (renal lymphoma), central nervous system
(CNS lymphoma) or eyes. Sometimes rather than forming
solid lumps of cancerous tissue, malignant lymphoma cells
can diffusely infiltrate an organ or organs and this can be a
gradual process making diagnosis very difficult. In addition to
progressing to make your dog feel unwell and effects caused
by the position of the lymphoma (eg seizures in CNS
lymphoma, vomiting and diarrhoea in GI lymphoma),
lymphoma can have several strange remote effects on areas
of the body where it is not growing. These effects (called
'paraneoplastic syndromes') can include dramatic weight loss
even if appetite is unaffected, high calcium levels which lead to
excessive drinking and urinating and sometimes nerve
problems and skin problems.
Lymphoma is usually not a painful condition but is progressive
and debilitating. Some dogs with lymphoma will present as
emergencies if the lymphoma occurs in a place where it
compresses vital structures such as the brain, spinal cord or
airways.
How can lymphoma be diagnosed
Lymphoma can sometimes be very easy to diagnose
(especially in the case of externally accessible lymphoma) or
can be extremely difficult, especially GI or CNS lymphoma or
where the lymphoma is growing slowly into organs which are
not readily accessible to sampling.
Dick White Referrals, Station Farm, London Road, Six Mile Bottom, Newmarket, Suffolk. CB8 0UH
Tel 01638 572012, Fax 01638 572013

Canine Lymphoma
INTERNAL MEDICINE
All lymphomas can only be truly diagnosed with a tissue biopsy
examined by a veterinary pathologist and this may require
surgery (or even multiple surgeries) to be certain. In addition,
because the implications of lymphoma is that several areas of
the body may be affected and we need to be sure of knowing
the extent of the disease and the effects on other organs, we
usually have to do a series of blood tests and imaging
procedures (usually x-rays and ultrasound) and often bone
marrow evaluation. This process called 'staging' the tumour
allows us to gauge the extent of the disease which is important
in making treatment decisions (the same treatment is not
appropriate for all forms of lymphoma) and to give you an idea
of prognosis. Sometimes special pathology tests such as
„immunohistochemistry‟ may be recommended to distinguish
between the T and B-cell subtypes. There is no „blood test‟ for
lymphoma though there are some features which can be seen
on specialized blood tests which can make lymphoma more or
less likely
Chemotherapy is a very emotive word as most people
associate chemotherapy with the side-effects experienced by
most people receiving anti-cancer drugs. However, whilst in
people the intent of treatment is always to cure the disease
(meaning that powerful
Chemotherapy
being given to a dog
through an
intravenous cannula
placed in the right
foreleg. It is
important that
chemotherapy
drugs are
administered
carefully in this way
Can lymphoma be treated
Lymphoma is usually ultimately a fatal disease though it is one
of the few cancers which we can readily treat to make dogs feel
substantially better. Treatment will, in most cases, make the
disease go into remission (ie make the clinical signs disappear)
but this is unfortunately not the same as a cure as most dogs
will eventually relapse and their tumour will come back. Thus it
should be remembered that when we treat lymphoma we are
unlikely to cure it and ultimately the affected dog will still be
expected to succumb to the disease. Very occasionally we see
such long-lasting remissions that effectively the patient is cured
but this probably occurs in less than 10% of cases.
CHEMOTHERAPY
Untreated lymphoma usually progresses to such an extent that
euthanasia is requested on humane grounds within in 4-8
weeks of the clinical signs starting. Treatment of lymphoma
involves giving drugs to kill the tumour cells (chemotherapy).
“the goal of chemotherapy is to promote
quality of life…The overwhelming
majority of dogs treated for lymphoma do
not show side effects ”
Two of our dedicated medicine nurses administering
chemotherapy to a regular patient. Dogs are very tolerant of
chemotherapy and when we see them regularly become part of
„gang‟. Our medicine nurses regularly admit and discuss any
concerns with owners and are an important part of our team
approach to cancer patients
CHEMOTHERAPY
Dick White Referrals, Station Farm, London Road, Six Mile Bottom, Newmarket, Suffolk. CB8 0UH
Tel 01638 572012, Fax 01638 572013

Canine Lymphoma
INTERNAL MEDICINE
I am considering treatment; what factors should I
take into consideration
First some facts. As already stated dogs with lymphoma live an
average of 4-8 weeks before becoming so ill that euthanasia is
requested. If you do not elect to proceed with chemotherapy
then palliative therapy with corticosteroids can be given and
this will not increase life expectancy but generally makes dogs
'feel' better.
Chemotherapy drugs are mostly given by injection via an
intravenous cannula on an outpatient basis. These agents
need to be very carefully handled and blood tests are
needed before each administration.
CHEMOTHERAPY
cocktails of drugs with increased risk of side effects are the
norm and are tolerated by cancer patients), in our veterinary
patients we do not feel it ethical to treat if the treatment makes
the animal feel worse. We cannot explain to our patients that a
cure may be possible by experiencing short-term side effects
and so our aim is different – we want to make our patients feel
better (preferably completely normal) for as long as possible
and to experience good quality of life . This means that we
seldom cure the disease but hopefully we don't make them feel
bad either. Side effects in animals on chemotherapy that we
use are therefore rare (see separate information) and if we feel
that side effects are unacceptable we stop the treatment.
The decision to treat lymphoma can be an extremely difficult
one and it should be borne in mind that treatment of lymphoma
is an extremely large commitment in terms of emotion, time
(weekly visits to a vet or veterinary specialist are usually
needed and these need to be at strict times) and money
(treatment costs frequently add up to many hundreds or even
thousands of pounds over a period of months).
Not all pet owners wish to pursue chemotherapy and not all
patients are suitable candidates for treatment and in many
cases humane euthanasia may be the kindest option. There is
absolutely nothing wrong with making the decision for a pet to
be humanely put to sleep rather than suffer form a cancerous
disease and it is kinder for the pet to take this course of action
than to embark upon treatment which you do not wish to or
cannot for practical reasons pursue.
With some exceptions about 75-90% of dogs with lymphoma
will go into remission when treated with chemotherapy (less
likely with T-cell types of lymphoma). The remainder either do
not respond at all or respond partially and temporarily. Of the
dogs who respond the average length of their remission is in
the region of 6-12 months. Most dogs will then relapse and the
decision is usually made at that time either to perform humane
euthanasia, or to try another chemotherapy treatment. On
average treated dogs who respond will be expected to live for
about a year with good quality of life. A small proportion of
dogs that undergo chemotherapy will have very lengthy
remissions from their illness which may last 2 years or more.
Treatment usually involves using a combination of drugs (most
of these work better in combination than alone) called a
'chemotherapy protocol'. There are many types of protocol
used for dogs with lymphoma and all have similar success
rates, some slightly more than others. We therefore take into
consideration things like the type of tumour, the frequency of
monitoring and hospital visits needed, the cost of the drug
therapy and working schedule of the dog's owners. The drugs
are usually given in a specific timetable and either continued
until the lymphoma relapses or given for a fixed period of time
and then stopped (this depends on the type of protocol used).
There are certain features that we know will make the chances
of chemotherapy working in a dog a lot lower. These include –
having high levels of calcium in the blood, having involvement
of the bone marrow, having lymphoma of the gastrointestinal
tract, kidneys or central nervous system, and having lymphoma
which has been previously treated for instance with
corticosteroids. These factors all have to be taken into account
when you are deciding whether to go ahead with treatment and
which is why we try and get as much information as possible
before starting treatment.
With chemotherapy protocols there are some pros and cons of
different types of protocol which need to be balanced. We
know that in general, the chances of attaining the longestlasting
remission possible is seen with protocols that contain a
type of drug called doxorubicin (sometimes a drug called
Dick White Referrals, Station Farm, London Road, Six Mile Bottom, Newmarket, Suffolk. CB8 0UH
Tel 01638 572012, Fax 01638 572013

Canine Lymphoma
INTERNAL MEDICINE
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Some definitions
Remission
Successful eradication of identifiable lymphoma
Induction therapy
Chemotherapy given to initially put the tumour into remission
Chemotherapy protocol
A protocol is a combination of chemotherapy drugs where the
combination works more effectively than the individual drugs
separately
Continuous / discontinuous therapy
A dog with lymphoma causing enlargement of the lymph
nodes under the angle of the jaw which can be seen to be
enlarged (arrows)
epirubicin is used instead). These protocols often require access to
specialised handling facilities (as these drugs are very hazardous
to veterinary personnel preparing them) and necessitate some
special monitoring for toxicity to the heart. For this reason these
protocols have an increased chance of success but are also more
costly, involve more frequent travel to a veterinary specialist centre.
Other protocols do not have these drawbacks, but similarly do not
have quite the same degree of success. Additionally veterinary
practices vary greatly in how experienced they are in handling
chemotherapy drugs. Administration of these products is
hazardous to veterinary personnel and in practices where the
number of cancer patients seen is low, chemotherapy may not be
available
We will generally, when deciding what sort of chemotherapy to use,
take into account your own practical wishes, costs, your willingness
to travel, the availability at your vet of chemotherapy, the type of
lymphoma and the temperament of your dog. We aim to then reach
a consensus of what the most practical and effective treatment is
likely to be. Remember that the important thing is that any regime
embarked upon is practical for you and your dog rather than
necessarily the one that yields marginally better results than
others.
What happens if lymphoma recurs
If the lymphoma recurs then either a type of rescue chemotherapy
can be tried or euthanasia may be considered. The chances of
subsequent chemotherapy achieving remission, and if successful,
the duration of that remission, gets much poorer with each relapse.
In the past much chemotherapy was given continuously with
a gradually increasing interval between doses. Many newer
regimes involve chemotherapy being discontinued after the
induction course. This does not result in higher risk of
relapse.
Relapse
Rescue
Recurrence of the lymphoma
Chemotherapy treatment given to treat relapse
KEY POINTS about Canine Lymphoma
Chemotherapy is the mainstay of therapy.
Quality of life is as important as keeping the
disease in remission
Side effects are very rarely seen but it is
important that regular blood tests are taken
to „pre-empt‟ problems so that they can be
avoided
Chemotherapy is a large commitment in
terms of time, emotion and finance
Dogs that are in remission from lymphoma
will act normally and be free of signs of their
disease
Dick White Referrals, Station Farm, London Road, Six Mile Bottom, Newmarket, Suffolk. CB8 0UH
Tel 01638 572012, Fax 01638 572013