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Cancer Therapy for the Geriatric Feline
by Christi Benigni
Spring 2009
This paper is written in hopes to give feline caregivers
general knowledge of cancer as well as an understanding
of the diagnostic and therapeutic options
that could potentially be offered to their feline companion.
Cancer is a very complex disease including many different types,
with each type offering a multitude of therapeutic options.
This article should be used as a guide in combination
with a general veterinary practitioner and veterinary oncologist,
to assist a caregiver in asking appropriate questions
and making an informed decision that will ultimately offer
their feline companion the best quality of life and comfort.
What is Cancer?
Cancer is generally believed to arise from changes in a single cell,
giving rise to uncontrolled, unorganized, and purposeless growth
of a single cell line.
Normal cellular division creates a constant flow of injured genes
that are regularly corrected by innate repair mechanisms
present in normal cellular function.
By escaping these regulatory restraint mechanisms
these "renegade" cells continue to grow and divide
using the same mechanisms as normal cells
making their divisions uninhibited, reckless,
and a foundation for cancer.
Cancer is generally classified and named based on the cell of origin.
Although the term cancer is defined as one encompassing disease,
there are over one hundred different types of cells in the body,
each having the potential of giving rise to cancer.
Since cell types serve different functions within the body,
this allows for unique variations, characteristics, and behavior
when inflicted with cancer.
Different types of cancer have an affiliation for different systems
within the body.
For instance some may come in the form of a tumor within the skin,
whereas others may target a specific organ.
Cancer may also be present in a diffuse nature
without the existence of any focal lesion
and may be attacking cells within the blood or lymphatics
and associated lymph nodes.
Diagnosis
Diagnosing cancer in a geriatric feline patient can be challenging
due to initial signs being subtle and often camouflaged
by general signs of aging, such as "slowing down", lethargy,
reduced appetite, dental disease, changes in weight, muscle loss,
and abdominal distension.
Detecting cancer in the earliest possible stage
offers the geriatric feline the best chance of survival from cancer.
In the presence of a tumor or lesion a fine-needle aspirate (FNA)
should be performed to help identify the tumor.
FNA offer the benefit of possibly identifying the presence of cancer
both inexpensively and non-invasively by simply placing
a needle into the tumor and pulling back a sample of cells.
Although this procedure can be invaluable it also has the potential
to be inconclusive and offers little information on the overall behavior
of the cancer due to its limited sample size.
To properly identify the behavior of the cancer
a surgical biopsy sample will often need to be performed.
FNA of regional lymph nodes adjacent to a tumor is also imperative
in evaluating the invasiveness of the cancer.
With or without the presence of a tumor or lesion
a complete-blood-count, biochemistry profile, assessment
of thyroid function, urinalysis and determination of
Feline leukemia/Feline immunodeficiency virus status
should always be performed to evaluate the feline's overall health
as well as to help classify and prognosticate the cancer.
Abdominal and thoracic radiographs should be performed
to identify the presence of tumors,
and evaluate the invasiveness of the feline's cancer.
The thorax is one of the most common places for cancer
to metastasize, and its presence is an important prognostic indicator.
Although radiographs serve as a good scan of the animal,
many small lesions can be missed,
therefore more specialized modalities are available
such as ultrasound, magnetic resonance imaging and computed tomography
to pinpoint lesions not detected by radiography.
When a feline is diagnosed with cancer
a prognosis will often be given in the form of a percentage.
This percentage is based on statistical analysis of other cats
diagnosed with the same or similar cancer
and their average response to therapy.
These statistics often do not take into consideration
the age of the cat at diagnosis or any concurrent disease states.
It is important to understand that this figure is not a guarantee
but an educated guess and that some cats may respond
significantly less than or more than the predicted outcome.
Treatment
When treating cancer in the geriatric feline
it is important to first approach treatment and care
with the understanding that "age is a condition not a disease".
Treating cancer in geriatric felines is more complex
often due to concurrent ailments or compromise to other organ systems,
posing limitations in both the drugs administered
as well as anesthetic risks.
Although daunting, it is important to understand
that this is not an impossible task and can be very rewarding
and well worth the effort.
Each patient should be approached on an individual basis
to provide the most optimum treatment protocol for his or her
health and well-being.
There are numerous treatment modalities
that can be tailored and combined to reduce toxic levels
and offer ultimate comfort to your companion.
Chemotherapy
Chemotherapy acts on rapidly dividing cell populations
by interfering with DNA synthesis or cell division.
In an ideal situation chemotherapeutic drugs would only target
the cancer cells without causing any harm to normal cells.
However, unfortunately and at least at this time,
such a drug is not in existence.
Chemotherapy is toxic and kills by percentage.
Meaning the goal of chemotherapy is to consistently kill
a high enough percentage of the diseased cells
to suppress the cancer's progression,
while not jeopardizing the overall health of the patient.
In general, chemotherapy is often associated with preconceived notions
from people's own experience with human chemotherapeutic modalities.
Research has shown that although side effects do occur
with chemotherapeutic drug use in veterinary patients,
animals tend to have decreased effects in regards to nausea and weakness.
In people, higher doses are used resulting in a much greater risk
of side effects as doctors are hoping for
a very long-term duration of remission.
For example, it seems reasonable to risk making a person extremely ill
for six months to gain twenty years of life.
However, in the case of treating a geriatric feline,
whose average life duration is fifteen to seventeen years,
six months with the risk of severe side effects
isn't a practical option.
Instead it is more reasonable to use a lower dosage
and strive for four to five cancer-free years.
Felines on chemotherapy may experience some hair loss,
most commonly with the loss of their whiskers.
The hair will usually grow back,
however the hair may be a different color or texture.
There are a large variety of chemotherapeutic agents,
each containing their own unique properties of killing cells
at different stages.
For this reason, it is common to use a combination of drugs,
referred to as a "protocol".
With the guidance of a veterinary oncologist
all options of treatment can be presented along with the prognosis
they offer.
Once again concurrent disease, such as renal disease, liver disease,
hyperthyroidism, heart disease, just to name a few, could eliminate
some specific drugs from use due to their direct effects on organs
or routes of metabolism and excretion.
Chemotherapeutic drugs come with the risk of side effects,
including increased urination and thirst, nausea, vomiting, diarrhea,
anorexia, bone marrow suppression, heart disease, renal disease, and
blindness.
However, each drug is associated with its own variation
of these side effects and with the guidance of an experienced oncologist
and the individual health of each patient
the benefits and risks can be weighed
and options to avoid and diminish these risks can be discussed.
For instance a drug may be initialized at a decreased dose
with the possibility of being slowly increased
to allow for early detection and interference of toxic events.
Chemotherapeutic drugs can also be offered with different routes
of administration.
The majority of regimens require repeated intravenous administration,
requiring the placement of an intravenous catheter
to prevent the drug from exiting the vein and causing necrosis and sloughing
of surrounding tissue.
Some of these drugs must be given slowly over a couple of hours
along with fluid therapy, requiring hospitalization for the day.
For some felines intravenous therapy is a realistic option,
whereas for others the stress of repeated veterinary visits
and the placement of an intravenous catheter is overwhelming
and could greatly affect the animal's overall quality of life.
It is therefore important to understand that there are chemotherapy protocols
that reduce the number of necessary administrations,
could simply be administered as an injection under the skin,
or even orally from home, eliminating veterinary intrusion altogether.
Most oral chemotherapeutics are coated to protect any adverse effects
to the person administering the medication
in addition to the use of latex gloves for optimum protection.
Oral chemotherapeutics are also one of the more inexpensive options
available in comparison to other chemotherapeutics.
Feline alimentary lymphoma, cancer of the gastrointestinal tract,
is one of the most responsive types of cancer that can be treated
with multi-agent chemotherapy.
Alimentary lymphoma is currently the most common cancer
seen in geriatric cats.
The extent of the cancer will determine the treatment,
however in cases where there is more than one lesion
within the gastrointestinal tract and surgical removal is not an option,
chemotherapy offers the best prognosis,
estimating to achieve remission in approximately 87% percent of cats
and offer a survival time of 49-210 days.
Surgery
Surgical removal remains the best option in providing a cure
for certain types of cancer in cases where a solitary tumor
is present with no associated metastasis.
During removal the surgeon will strive to obtain 3 cm margins
in all directions of the tumor.
This results in a large incision in relationship
to the size of the tumor removed.
In general the perimeter of the tumor contains the most aggressive cells,
as they are the ones responsible for spreading the cancer
to associated healthy tissues and increasing its size.
To ensure that clean margins are obtained all removed masses
should be submitted for histopathology.
In cases where cancer cells are still present along the periphery,
another surgery should be performed promptly
or radiation or chemotherapy therapy should be instituted
to reduce its ability to spread.
In cases where masses do return they often are more aggressive
than the initial tumor because as stated above
the more aggressive cells at the periphery are what were left behind.
Radiation
Radiation therapy is the use of a very small narrow beam
to deliver a dose of radiation, much higher than a typical x-ray,
to treat cancer by interfering with the cancer cells' ability
to divide and reproduce.
Because beam location must be exact to target the area of the tumor,
feline patients must be anesthetized to remain perfectly still.
Therefore, it is important for the caregiver to understand
that their companion will be undergoing repeated,
short, durations of anesthesia.
Once again, as with the chemotherapy mentioned above,
this might not be an issue for some cats,
however for others that are easily stressed
or have concurrent health issues making them an anesthetic risk,
radiation therapy might not be the best option.
Radiation therapy has a number of benefits.
It can be used alone as a single therapy,
or combined with surgery or chemotherapy.
Radiation may be used prior to surgery to shrink the size of the tumor
to assist the surgeon in obtaining larger clean margins
when removal is performed, as well as after a surgery
if clean margins were not obtained.
In cases where a cancer involves the bone,
radiation therapy can be instituted as a relief of associated pain.
Side effects of radiation therapy vary with the location being treated.
The majority of felines will lose their hair where the beam is aimed.
In contrast to chemotherapy some of these cats' hair will not grow back.
Radiation could cause an inability for some tissue to heal
resulting in skin ulcerations or sloughing of the skin.
These lesions serve as a source of pain and therefore pain control
should be instituted to keep the cat comfortable.
Lesions typically do not develop until midway through the protocol.
It is important to understand that stopping a radiation protocol
too early can result in a drastic drop in the tumors ability
to respond to subsequent therapy.
Therefore, pain medication should be prescribed along with supportive therapy
to aid the cat in finishing their prescribed treatment.
One common location of cancer in geriatric cats is the oral cavity.
The more common types of cancer at this location include,
squamous cell carcinomas and fibrosarcomas.
Surgical removal is not always an option in these locations
due to the limited amount of tissue and the associated difficulty
in closing the incision after tumor removal.
In these situations, radiation serves as an option
to control the growth and invasiveness of the tumor.
When radiation is used in the treatment of these mucosal lesions
the mouth could become dry or cracked and sometimes even cause drooling
or a foul odor.
Immune-suppression
In situations where the above treatment modalities
are determined as poor options,
immune suppressive doses of corticosteroids could be instituted.
There are a variety of reasons for the choice of this therapy
either due to the extent of the cancer, concurrent disease,
behavioral and personality limitations, or cost.
Immunosuppressive corticosteroids serve as an inexpensive option
that can inhibit the progression of the cancer,
and can prolong the patient?s life and comfort.
This therapy can be provided both inexpensively
and through the comfort and convenience of home care.
Corticosteroids are also associated with side effects,
most commonly seen as gastric ulceration, increased hunger and thirst,
as well as increased urination.
When using corticosteroids
there are two important general factors to recognize.
One, you can never stop a corticosteroid abruptly.
Instead you must gradually taper the dosage
as prescribed by your veterinarian because when a corticosteroid
is given (exogenously) the body's mechanisms (endogenously)
to make its own corticosteroids is suppressed.
Therefore, it takes time for the body to compensate for a decline
in exogenous corticosteroid administration and to produce its own
for body functional requirements.
The second important factor when using corticosteroids is that
it can not be combined with a non-steroidal anti-inflammatory drug (NSAIDS),
which is commonly used in the treatment for pain.
When used together these drugs produce a severe,
hemorrhagic gastrointestinal ulceration
that could result in gastric perforation.
However, there is no benefit in ever using these two drugs together
since corticosteroids work in a very similar fashion as NSAIDS
and have a remarkable effect on alleviating pain
of an associated tumor by reducing inflammation.
Pain control
The number one goal of cancer therapy is usually not to cure the cancer,
but to prolong the life of the animal in a comfortable fashion
making pain control the number one priority.
There are many drugs available to aid in doing this
by reducing inflammation as mentioned above with either NSAIDS
or corticosteroids.
A common NSAIDS used in cats is Meloxicam.
There has also been research that has indicated that
this class of drug may have an inhibitory effect on cancer.
The exact mechanism is not completely understood,
however it is believed that the effect is stemmed
from its cox-2 inhibition and its action against
tumor producing inflammatory mediators.
Other drugs used to reduce pain are within the Opioid family.
There are assortments of drugs to choose from in this category
allowing a wide variety of methods for administration.
These drugs can be given as an injection, orally,
or in the form of a patch.
A fentanyl patch can be placed over a shaved region of the cat's body
and will offer constant delivery of pain management
for a three-day duration.
Coping with a Cancer Companion
Unfortunately, the majority of geriatric cancer patients
will eventually succumb to the disease of cancer
either directly or from coexisting health factors.
The dread of losing a companion can be a significant emotional burden
for a caregiver and can be associated with depression,
frustration, guilt, remorse, and grief.
The bond between a companion and a caregiver is extremely powerful
and during a battle with cancer there is a profound feeling
of love and anticipatory loss.
It is important to know that this is normal,
and there is support available.
In addition to the support of your veterinarian
there are other resources to aid caregivers during this difficult time.
Pet-loss counseling does exist, both on an individual basis
as well as group therapy.
Counseling is available for free at many veterinary universities
through the form of a hotline service.
There are also pet cancer support groups on the internet
that allows caregivers the opportunity to share
both their experiences and feelings in a safe peer group.
Although at times aiding a companion in their battle against cancer
can seem overwhelming, the experience can also be very rewarding.
Cherish the time you spend with one another and pride yourself
on the ability to care for and relieve your companion from pain.
The connection between an animal and human is a unique
and cherished relationship that should be honored and treasured.
Caregiver Resources
The Animal Medical Center -- Human-Animal Bond Programs
New York, (212) 838-8100
Discussion group:
www.amcny.org
The Pet Loss Grief Support Website
www.petloss.com
University of Florida -- Grief counseling
(352) 392-4700, 1+4080
Washington State University -- Pet Loss Hotline
1-(866) 266-8635
www.vetmed.wsu.edu/PLHl/
References
Eldredege, Debra DVM, Margaret H. Bonham.
"Cancer and your pet".
Capital Books.
2005.
Fidel, Janean DVM:
VM 552 Small Animal Medicine notes, Oncology.
Washington State University.
February 2009.
Marretta JJ, Garrett LD, Marretta SM:
Feline oral squamous cell carcinoma: and overview.
Vet Med.
June 2007.
Milner RJ, Peyton J, Cooke K, et al:
Response rates and survival times for cats with
lymphoma treated with the University of Wisconsin-Madison
chemotherapy protocol: 38 cases (1996-2003).
J Am Vet Med Assoc 227:1118.
2005.
Villalobos, Alice DVM, Laurie Kaplan MSC.
"Canine and Feline Geriatric Oncology, Honoring the Human-Animal Bond"
Blackwell Publishing.
2007.
This paper is dedicated in loving memory to Edd.
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