Lymphoma, lymphosarcoma and feline leukemia are alternate names for a tumor of the lymphocytes. This tumor may occur as a single mass or as multiple masses. Early cases usually occurred in young cats but since the feline leukemia vaccine became available the disease pattern has changed and we see most of our cases in older animals. These often involve the liver, intestine and kidneys. Below is a helpful discussion.
Feline Lymphoma By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com |
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Lymphoma in cats, as in dogs, is classified based on the
anatomic area that seems most prominently affected by the tumor. In
dogs, the most common lymphoma form is the multicentric form, where all
the peripheral lymph nodes of the body seem to enlarge at once. While
this can certainly occur in cats, the most common feline form of
lymphoma is currently intestinal. This was not always the case. Years
ago, prior to the widespread use of the feline leukemia vaccine, the
mediastinal form (a tumor in the chest cavity) was the predominant
lymphoma form and the leading cause of lymphoma was the feline leukemia virus.
Now that the virus has become less common, thanks to more cats living
indoors, effective vaccination, and readily available testing
procedures, causes of lymphoma are more obscure. Cigarette smoke in the
home has been found to double a cat's risk though genetic issues;
environmental chemicals and unknown factors remain under consideration.
Lymphoma can occur anywhere in the body where there is lymph tissue.
A
sick cat undergoes a battery of diagnostic tests and somewhere in the
course of the work-up cells are discovered, either in biopsy, aspirate,
or even circulating in the blood that tell us that the cat has lymphoma.
Now what?
Can my cat be cured?
Theoretically, yes,
but practically speaking, no. It is best to focus on a realistic
outcome, which is the longest possible survival with good quality life.
Different treatment protocols are associated with different disease-free
intervals. See below for more details.
How does lymphoma cause death?
Lymphoma
is a rapidly growing malignancy that is able to go and grow anywhere
where there is lymph tissue, which is virtually every organ in the body.
Eventually, the cancer will infiltrate an organ to such an extent that
it fails (often this is the bone marrow or the liver). The patient loses
his/her appetite, vomits or gets diarrhea, weakens, and dies. At some
point the tumor becomes resistant to therapy and no further remissions
can be obtained.
Chemotherapy
The word chemotherapy conjures images of the bald Elizabeth Perkins from The Doctor or the bald and vomiting Campbell Scott in Dying Young.
It is unfortunate that many pets (and probably people, too) do not
receive chemotherapy based upon these unpleasant images that do not
truly represent the current state of treatment response. Chemotherapy
simply means therapy using medication (as opposed to therapy using
surgery or radiation). We hope that you will open your mind to what
decades of research and clinical experience tells us about chemotherapy
rather than listening to what Hollywood has to say on the subject. The
following are common questions pet owners commonly have regarding
chemotherapy for their cat.
Should we see an oncologist?
It
is never wrong to see a specialist. Lymphoma is such a common
malignancy in humans that there are always new drugs, new protocols and
experimental therapy that your regular veterinarian may not be familiar
with. Seeing a specialist may be the best way to present you with all of
your options. If you are interested in this, ask your veterinarian for a
referral.
Will chemotherapy make my cat sick?
Probably
not. Nausea and infection are possibilities but most cats do not
experience any such complications. Only 7% of patients require
hospitalization due to side effects of chemotherapy. The bottom line
here is to know that animals rarely get sick from chemotherapy but that
you should know what to do in case of a problem (see later).
Will chemotherapy make my cat lose his hair or go bald?
While whiskers are commonly lost, substantial hair loss is not experienced by animals on chemotherapy for cancer.
How will I know when we have achieved remission?
A
patient in remission is indistinguishable from a completely cancer-free
patient. The lymph nodes will go down to normal size and if there were
any signs of illness related to the cancer, these should resolve. There
is approximately a 75% chance of achieving remission regardless of
protocol selected.
How will I know when we have lost remission?
The
most obvious sign will be that the lymph node enlargement has returned.
This means that the cancer is now resistant to the drugs being used and
new drugs must be chosen. (This is called a ?rescue?.)
How long will my cat have quality life on chemotherapy?
This
depends on what protocol you choose and there are many. There are also
many factors that influence how an individual will do relative to the
?average? response. Important parameters to note when reviewing a
protocol are: 1) the disease-free interval (i.e., how long the patient
is free from illness; 2) survival time; 3) typical duration of
remission; 4) expense; 5) and scheduling.
We will center on intestinal lymphoma as it is currently the most common.
Intestinal Lymphoma
Intestinal
lymphoma is now the most common form of lymphoma in cats. The average
patient is an elderly cat with a history of vomiting, diarrhea, weight
loss, appetite loss or any combination thereof. Patients are generally
older cats (median ages ranging from 9 to 13 years depending on the
study) with a tendency for male cats to be more predisposed to
development of the condition than female cats.
An actual mass may
develop with intestinal lymphoma or the tumor may be more infiltrative.
An actual mass can potentially cause obstruction in the intestine and
lead to a crisis that must be promptly resolved surgically.
Diagnosis
of intestinal lymphoma is best made by biopsy and if a mass is present,
it can be surgically removed at the time biopsies are taken.
Alternatively, the mass can be aspirated (cells removed via syringe) and
the cells analyzed in the lab. This may not be as definitive as biopsy
but is often adequate; surgery, of course, enables the removal of the
growth (if there is one) and relieves the obstruction.
It is
important to understand that no matter how localized the tumor appears
to be, simply removing the mass is not going to be curative; some kind
of chemotherapy is necessary for best chance at long-term survival.
The
more infiltrative forms of intestinal lymphoma do not create actual
growths; instead the intestine may only be abnormal under the
microscope. It is very difficult to distinguish inflammatory bowel disease
from lymphoma without a full-thickness biopsy (a full-thickness piece
of intestine) obtained via exploratory surgery. A less invasive method
of obtaining a sample is via endoscopy, usually adequate for diagnosis
but full thickness biopsy samples cannot be obtained this way.
- Cats with intestinal lymphoma treated with prednisone
alone have a life expectancy of 45 to 60 days. Other protocols using
multiple drugs yield much better results (see below for details).
*Lymphoma
is graded by the pathologist reading the tissue sample as either
high-grade, low-grade, or intermediate-grade. The grade refers to how
rapidly the cells appear to be dividing and how malignant they appear
with high grade being the most malignant. The grade of lymphoma bears
on its response to chemotherapy (see below). It is not possible to
determine lymphoma grade from a tissue aspirate; an actual piece of
tissue must be submitted for biopsy. As a general rule with lymphoma,
higher grades tend to be more responsive to chemotherapy drugs. With
feline intestinal lymphoma, however, it is the low-grade cases that are
capable of fairly long remissions.
* As with dogs, chemotherapy
protocols are associated with minimal side effects. Many protocols have
been described for the feline lymphoma patient.
- In one study 7 cats were treated with the COP protocol (cyclophosphamide, vincristine, and prednisone). Of
these 7 cats, 6 achieved remission with a median duration of remission
lasted 19 weeks. The grade of intestinal lymphoma was not considered.
- In a study from the Netherlands (Journal of Veterinary Internal Medicine
Mar/April 2002), 61 cats with lymphoma were treated with the COP
protocol. Of these cats, 75% achieved remission with 51% still
disease-free after 1 year and 38% disease-free after 2 years. Median
survival time for the group was 266 days. Complete remission was
necessary for long term survival; cats with partial remission were
unlikely to survive one year. Siamese cats had a more favorable
response than cats of other breeds.
- In one study, 14 cats were treated with cyclophosphamide, vincristine, and methotrexate. Median survival time was 12 weeks. The grade of the intestinal lymphoma was not considered.
- In another study, 132 cats with lymphoma were treated with COP plus doxorubicin, L-asparaginase,
and methotrexate (the "CHOP-like" protocol). Of this group 125 cats
had intestinal lymphoma. Out of the total 132 cats, 67% achieved
remission with a 21-week disease-free interval. Another study using the
same protocol on 21 cats with intestinal lymphoma, only 38% achieved
remission but these cats had disease-free interval of 40 weeks.
- In
another study, 25 cats with intestinal lymphoma, 25 of which had
high-grade lymphoma, were treated with COP. Those who achieved complete
remission had a 30-week disease-free interval. The overall median
survival when all 25 cats were considered was only 7 weeks.
- As for low-grade intestinal lymphoma, a study of 50 cats included 36 treated with prednisone and chlorambucil. Here, 69% achieved complete remission for a median duration of 20.5 months.
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