|
Canine Chemotherapy Drugs
|
|
Chemotherapy
treads
a narrow path between effectiveness and toxicity. In fact,
chemotherapeutic protocols are most often limited not by the ability of
drugs to kill tumor cells, but by their toxicity to the patient. The
goal is to destroy as many malignant cells as possible while leaving
enough normal, "organized" cells to recover organ function. It is
important, therefore, that we use the highest dosages that we think the
patient can tolerate. The more cancer cells surviving any one time, the
sooner the patient will become resistant to the beneficial effects of
the drugs.
Risks to People Living
with Chemotherapy-treated Pets
The anti-cancer drugs are excreted from the animal's body via urine and
feces. This usually happens in the 48 hours following treatment, but
can
be as long as 5 days for Adriamycin. If it is possible, you should try
to
have the animal eliminate in an area away from the immediate yard or
play
area. Cat boxes should be changed regularly, and waste material handled
with
a scoop. If urine or feces must be handled, use heavy rubber or latex
gloves
and disposable wipes/towels. Place all waste/towels in a plastic bag
and
seal it, before disposal. Smooth surfaces may be washed with a dilute
bleach
solution (1/4 c. to 1 gallon of water). Humans and other household pets
living
with treated pets are generally thought not to be at any health risk,
just
as in the case with humans. Pregnant women should not handle ANY animal
waste
or anti-cancer medications. If any family member living with the pet
has
a condition that would suppress his/her immune system, it would be
prudent
to let the veterinarian know.
source:http://www.portlandvetspecialists.com/library/cancer7.html
Chemotherapy
Basic Information for Pet
Owners
Chemotherapy refers to any drug given for therapeutic reasons.
Technically, antibiotics are chemotherapy. However, common use has
changed the term
to refer almost exclusively to treating cancer. In this context,
chemotherapeutic agents (chemotherapy drugs) are those that kill cancer
cells. The best
chemotherapy drugs are those that kill only cancer cells, and leave
normal
body cells alone. Unfortunately, these drugs are rare to non-existent.
There
are always civilian casualties' in the was against cancer.
Chemotherapy is the single most effective method of treatment for some
cancers (like lymphoma or lymphosarcoma) and offers an opportunity for
extension of life along with good quality of life during therapy. We
will
also recommend chemotherapy after surgical removal of some tumors.
There
are two reasons for this: to stop the recurrence of the tumor in the
same
location, and to inhibit its spread to distant parts of the body (a
process
called metastasis). Although we do not offer radiation therapy at our
clinic,
chemotherapy is sometimes used in conjunction with radiation in order
to
make the radiation more effective at killing the cancer cells.
Cancer cells tend to be rapidly replicating (reproducing), which is why
cancers spread so quickly, and why tumors can grow so rapidly. The
drugs used to treat cancers affect rapidly growing cells the most. They
are often drugs that interfere with the cell's DNA, and so kill the
cell when it tries to divide. In order to be effective, these drugs
need dividing cells like those present in tumors.
The collateral' damage happens mostly to other rapidly dividing cells
in the body like the bone marrow and the lining of the stomach and
intestines. These cells are the ones hardest hit by chemotherapy drugs,
and the effect on these cells are what cause the problems we associate
most with chemotherapy.
Side effects
The most common adverse effects of chemotherapy are on the
gastrointestinal tract. We typically see nausea, vomiting, and possibly
diarrhea. Because most animals are not good at telling their owners
that they feel nauseated, and because most owners are unaware of the
subtle signs of nausea, we usually dispense an anti-nausea medication
that is given at home for a day or two after each chemotherapy
treatment. We give it to patients in the hope of forestalling any
vomiting, or helping if the pet does experience nausea.
A few key signs of nausea are lip-licking, drooling, and lack of
appetite.
The most serious effect of chemotherapy drugs is their effect on the
rapidly dividing cells of the bone marrow. The marrow contains
undifferentiated
blood cells that will develop into the many different cells that
populate
normal blood. We are concerned mostly with the cells that are the
"parents"
of the white blood cells. White blood cells fight infection, and a
serious
depletion in their numbers, as can happen when the bone marrow is
affected
by chemotherapy drugs, can leave the pet vulnerable to serious
infection.
Sometimes this infection can become systemic and enter the bloodstream,
a
condition called sepsis. Sepsis is a potentially life-threatening
condition.
A much less common problem is hair loss. Few dogs experience real hair
loss when undergoing chemotherapy. The exception to this is a breed
with continuously growing hair, like the Lhasa Apso, Poodle, Shih Tzu,
Old English Sheepdog, Puli, Maltese, and some Schnauzers. We will
sometimes see significant hair loss in these dogs early on in the
treatment protocol. This hair will grow back once chemotherapy stops,
or even when the frequency of drug administration is decreased. Also,
not all dogs of these breeds experiences hair loss;
it is an individual thing.
An additional adverse reaction that can occur with some types of
chemotherapy drugs is an extreme tissue reaction to the drug if it
accidentally comes in contact with the tissues around or outside of a
vein. If the drugs leak out of the vein, or are accidentally injected
outside of the vein, severe necrosis (death) of the surrounding tissue
can occur. Needless to say, this is a very infrequent occurrence as
every precaution is take to prevent it, including using long
intravenous catheters and sedating pets who are at
risk of dislodging a catheter during chemotherapy administration. The
drugs
most commonly associated with this tissue reaction are doxorubicin,
vincristine, and nitrogen mustard.
Other side effects are quite drug-specific.
Doxorubicin treatment carries with it a risk of cardiotoxicity (heart
damage).
The platinum agents (cisplatin and carboplatin) can be very toxic to
the kidneys.
Cyclophosphamide can cause sterile cystitis (bladder inflammation).
Vinca alkaloids (vincristine, vinblastine) and platinum agents can be
neurotoxic.
L-asparaginase and many other drugs can cause acute allergic and
hypersensitivity reactions.
CCNU (Lomustine) and other drugs. can be toxic to the liver.
Monitoring
All patients undergoing chemotherapy will need regular blood testing.
The majority of the tests will be checks of the blood cell counts. We
will also need to evaluate the liver and kidneys on a regular basis
("regular" depending on the type of protocol being used). As a rule of
thumb, blood counts are done 7-10 days after the dose of
chemotherapeutic drug. There are variations on this, and you will be
informed of the schedule for your pet before we start his or her
treatment.
Quality of Life
Chemotherapy is meant to prolong life, not to prolong dying.
It is not cruel or inhumane to opt for cancer chemotherapy for your
pet. Most animals that undergo chemotherapy have a very good quality of
life. They are happy, eating and drinking, and interacting with their
families. Most have normal energy levels most of the time. There may be
a day or two right after the chemotherapy treatment day where the pet
feels "off", but we try to minimize any of the detrimental chemotherapy
effects as much as we can. Also, we can stop at any time. If you, the
pet's owner, feel that his or her quality of life is poor during
chemotherapy we can stop giving the drugs. Many owners enter into
chemotherapy with some trepidation, and discover that the reality is
nowhere near as bad as their expectations.
The Cure
Cancers are rarely cured. In most cases we hope for remission of the
tumor, or remission of the cancer effects that are making the pet feel
sick. Some cancer types offer the hope of long remission times, but
there
are always variations.
We have to face the sad reality that most pets who have cancer, even
if they have chemotherapy, will eventually relapse. We will be faced
with
the decision of when and whether to euthanize. As always, this decision
should be made by loving owners based on their knowledge of their own
pet,
and with his or her quality of life always in mind.
Pain management
Many clients are concerned that their pets are experiencing pain with
their cancer. Control of pain is one of our top priorities, not only
from a humane aspect but because animals in pain do not respond as well
to therapy and do not heal as well.
We work with all of our clients to optimize pain relief for their pets
and minimize discomfort.
Nutrition
Cancer patients need to eat to stay strong and have the resources to
handle chemotherapy and the effects of the cancer. We encourage all
owners
to encourage their pets to eat. Warming the food and providing a
stimulating
environment is sometimes all that is required. For other patients, the
best was to get nutrition in is via a feeding tube. These can be
minimally
invasive and extremely well tolerated. Sometimes appetite stimulants
will
help. Supplemental amino acids, omega-3 fatty acids and a good vitamin
and
mineral supplement (such as Canine Plus) also assist in the patient's
recovery.
The Practicalities
Most chemotherapy drugs are given by intravenous injection or infusion
through an intravenous catheter. This means that an intravenous
catheter is placed and secured. The chemotherapy drug is injected
through the catheter with a syringe, followed by a copious flushing
with saline. Drugs that take longer to infuse (like doxorubicin) will
be delivered via a regular intravenous drip over a period of time.
Depending on the drug (and that can vary by the week in some
chemotherapy protocols) you should plan on the entire visit taking
about 30-45 minutes (for injections or rapid infusions) or up to 3
hours for longer infusions (typically doxorubicin). You will be
informed of the appointment length
when you book.
The cost of the treatments will depend on the medications.
Chemotherapy drug costs vary wildly, from $20 (£10.00 approx.)
per treatment to $750, (£375.00 approx) depending on the drug and
the size of the patient. There are also attendant costs for the actual
procedure, whether it involves an IV catheter and injection or a full
intravenous setup. You will be informed of the cost, if you so desire,
before starting any chemotherapy protocol.
Chemotherapy can last anywhere from a few weeks to several months to
lifelong, depending on the type of cancer being treated and the therapy
protocol used.
Emergencies
It is always a good idea that you keep a diary of your pet's
chemotherapy treatment. Noting the dates and drugs used for each
session, as well as the dates of follow up lab testing is very useful
to anyone treating
your pet in an emergency. Also have a written record of any oral
medications you may be prescribed, their doses and frequency.
Some emergencies can be directly attributable to the chemotherapy
treatment. Sometimes you just have "regular" emergencies. In either
case the veterinarian seeing your pet will need to know his history in
order to treat appropriately and choose medications that will not
interfere or worsen the effects of
the chemotherapy.
Take the bottles of any medications that have been prescribed for your
pet with you when you go to the emergency clinic.
reprinted
with kind permission from Animal Medical Hospital
The above information is simply
informational. It's intent is not to replace the advice of a
veterinarian nor to assist you in making a diagnosis of your pet.
Please consult with your own veterinarian for confirmation of any
diagnosis. Your pets life may depend on it.
