The Feline Leukemia Virus (FeLV) and the Feline Immunodeficiency
Virus (FIV) play an underlying role as the etiologic agent for the genetic
mutations found in Feline Lymphoblasts, the viral factor must be weighed
into account. Cats present in basically one of three different clinical
stages of disease: the truly ill, the symptomatic and the unaffected.
There is less optimism and less response for the very sick cats. We see
more success for the sick but stable cases, and good to great responses
for the asymptomatic cats.
Young cats may develop a large tumor in the chest cavity in front of the
heart (Anterior Mediastinal Mass, AMM). These poor cats will die quickly
without rapid diagnosis and treatment. The veterinarian can examine the
fluid aspirated from the chest cavity or the mass itself. If lymphoblasts
are found, the diagnoses can be made. If even one lymphoblast is found
in this fluid, the cat can be treated for lymphoma immediately and given
the chance to live.
Anything short of this quick action creates delay. Many cats with this
condition deteriorate quickly and the family is forced to elect euthanasia.
It is a shock to the owners because these young cats were healthy just
days before! Since they have over an 80% response rate, there should be
little hesitation to give chemotherapy to cats with AMM.
Most of our current cases of feline lymphoma are presented as intestinal
or mesenteric (membrane supporting organ/body) forms. The typical history
of weight loss, soft stool, diarrhea or vomiting should alert clinicians
to suggest a work up to rule out lymphoma. Cats with ropey intestines,
palpable mesenteric nodes, or obstructions are highly suspect for G.I.
lymphoma.
Cats that have the diagnosis of inflammatory bowel disease (IBD) are at
greater risk of developing intestinal lymphoma. IBD is considered a precancerous
lesion and lymphoma may be near at hand. The tricky part is knowing when
to abandon the treatment for IBD and go to the more intense chemotherapy
needed for lymphoma.
A fine needle aspiration (FNA) cytology is highly recommended by Dr.Villalobos.
A 1-1⁄2 inch 27 gauge needle is used to aspirate any structure in
the abdomen. Ultrasound guided FNA of mesenteric nodes and thickened bowel
loops is another way to get a non-surgical diagnosis. The next method
that bypasses the stress of surgery is with endoscopy (a fiber optic instrument
used to exam hollow organs).
Despite the fact that the wound may be below the mucosa for this technique,
enough cases are definitively diagnosed this way with little stress on
the cat. Laparoscopy (performance of a minor abdominal surgery using a
laparoscope) is becoming more available in private practices. Cats that
are weak and thin would be best served if the diagnosis could be made
via laparoscopy without open abdominal surgery. Finally, exploratory surgery
is elected as the only sure method to harvest multiple organ tissue and
full thickness intestinal samples.
Some cats will present an enlarged kidney or hepatomegaly. Ultrasound
and FNA can quickly establish the diagnosis for immediate treatment.
These cats can respond to aggressive immediate treatment if they are supported
with fluid therapy and nutritional support with hand feeding or esophageal
feeding tubes. It is possible to rescue cats from near fatal conditions
induced by lymphoma and to restore their well-being.
If the cat is FeLV and FIV negative, they have a better prognosis. One
of these viruses may be hidden in the cat in a dormant form and is most
likely the cause of the lymphoma. In viral negative cats, the survival
can be expected to last for one to several years. Many of our cases are
enjoying 2 to 5 +years remissions. Some have even discontinued the chemotherapy
treatments.
Dr. Villalobos recommends the Wisconsin based protocol for cats in these
cases. Administer of Vincristine at O.O25mg / kg i.v. along with 400 i.u.
/ kg of L-asparaginase S.Q. are often given on the first day. As a pre-treatment
for the L-asparaginase, we give Dexamethazone 0.1ml to 1 ml i.v. prior
to the Vincristine injection using the higher dose depending on the magnitude
of the cat’s tumor burden.
Prednisone at 5mg B.I.D. forever is dispensed along with two tablets of
25mg Cytoxan to be used orally on day #8 and #9. We instruct the owner
to return on day #15 for Adriamycin at 1mg / kg i.v. We also administer
Dexamethazone as above as a pre-treatment. We instruct the client to return
in one more week for Vincristine as above on day #21, repeat the Cytoxan
day #28 and #29, and then the second Adriamycin as above on day
# 32. Thereafter, we use a 10-day interval between treatments.
The cat returns for Vincristine every 21 days for 6 months. Ten days after
the Vincristine, the owner is to rotate the Cytoxan with oral Chlorambucil
giving one 2mg tablet B.I.D. or one tablet two days in a row only.
We place the entire chemotherapy regimen onto a calendar for the client
to use as a guide. This calendar is important and we ask the family to
keep notes on how the cat is doing on the calendar. After one year the
interval between treatments may be extended to two weeks.
For those clients who cannot return every 3 weeks, the schedule may be
adjusted to using the Chlorambucil 10 days after the Vincristine and the
Cytoxan 20 days after with a return at 30-day intervals for i.v. Vincristine.
Further adjustments may be made to accommodate the caregivers.
In response to client wishes, Dr.Villalobos has developed a stay at home
protocol that is called the “LU-C-LO-V” protocol,
which incorporates lomustine at 50mg / M2 after the Chlorambucil and Cytoxan.
This protocol is now being introduced to long-term cases and although
it seems to help keep cats in remission and at home, results are not compiled
for reference.
A CBC test must be done on all cats to monitor signs of Leukopenia, Anemia,
Thromocytopenia just prior to Chemotherapy treatment. They also need detailed
medical support for ongoing clinical symptoms and simultaneous disease
conditions.
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