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Cancer Treatments In Dogs
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Lumps and Bumps
Jane Alexander BVetMed., CertVA., MRCVS
Discovering your dog
has a lump can be terrifying. But finding out about the different
cancerous, and non-cancerous types, will help you to help your dog.
We all start to worry when we find a lump in our dog...could
it be cancer? We use so many other words to hide this worry.
Mass, growth and tumour all describe the development of an abnormal
area of tissue, either within the skin layers or in deeper structures.
In most cases, lumps that are close to the surface of the animal will
be found by the owner, while the deeper-seated types will usually be discovered
on clinical examination, or using special techniques such as radiography.
Not all lumps are cancer and lots of lumps are due to a variety
of other causes. They may be a reaction to a wound or a bite,
(ticks can leave a huge lump in the skin, due to the inflammation cause
by the tick's saliva), a sebaceous cyst, or a grass seed lesion.
Although some lumps are not cancerous, it may not be possible to tell
from examination. Within the 'cancer' group there are also the
benign types, which are usually single and not going to cause problems.
Its the malignancies which are. Unfortunately this classification is
not black and white either, since even 'benign' masses can become more
aggressive with time, and the degree of malignancy can range from the
reasonable to the downright horrid. Once we have ruled out the
obvious non-cancerous masses, which need their own lines of treatment,
we have to decide how to approach these cases.
A small soft lump that is freely moveable under the skin may
not cause a problem, and may be left, but always with the understanding
that it should be checked regularly and if the owner notes an changes,
the dog should be rechecked by the vet.
For other lumps, we will check the location. The approach
taken for each type will vary...so what can be done?
We need more information about the cells within the lump to
be able to advise on the best way to treat the dog. If the lump
is solid and 'discrete' (on its own), removal is often the best option,
and we will then send a portion of the lump to a laboratory, for histopathology.
A thin slice of the mass will be examined under a microscope
by a consultant pathologist, who will report back, describing the cells
and giving us a prognosis. If it is not possible to remove the
whole lump, we may take a biopsy or a 'fine needle aspirate'. Without
this information, it can be very difficult to decide on the right course
of action.
If the lump is more likely to be malignant, we may check, using
radiography and ultrasound, to see if there is evidence of the tumor
having spread to other areas in the body. The main sites we examine
are the lungs and the liver, but bones, spleen, and other organs can be
affected.
What do we do next?
We could remove the mass, and histopathology may have indicated
that this should be curative. In these cases, regular monitoring
of the operation site by the owner, and occasional checks by the vet
should be sufficient.
But if the test results show the mass to be malignant, the choice
of follow-up treatment depends on the type of tumour. Some are
controllable with radiation treatment, while others respond better to
chemotherapy, or to a combination of different techniques. Chemotherapy
can usually be done in normal 'general practice', and does not cause the
side-effects that we see in humans, as the doses are generally lower.
Radiotherapy is undertaken in referral hospitals, and usually requires
a general anaesthetic to keep the animal still during the exposure.
Whatever decision is made, our primary concern is the dog's
well-being. Quality of life is more important than quantity,
and should be at the forefront of our treatment planning. Many
of the techniques, such as radiotherapy and chemotherapy are expensive,
and insurance for veterinary fees can enable the owner to make decisions
based on the best care for the dog, without the worry over cost.
reprinted
with kind permission from Jane Alexander BVetMed., CertVA.,
MRCVS
Veterinary advisor to the Flat coated Retriever Society,
I cannot advise on specific diagnosis or treatments for
individual animals.
JaneA2000@aol.com
Surgery for Canine Cancer Treatment
If surgery is recommended
it is because the cancer is in an area of your dogs body that can be
reached by a surgeon. Surgical removal of localized cancer can often
be curative if the cancer was detected at its earliest stages, prior to
spreading to other parts of the body. Surgeons will often play a critical
role in managing your pet's cancer whether it is for obtaining a biopsy
sample, performing curative surgery, or alleviating symptoms caused by the
tumor.
Surgery is the mainstay
of cancer management but it is not always necessary. Pet owners should
engage in a detailed discussion with their veterinarian and veterinary oncologist
to ensure that all questions have been answered and a logical conclusion
about the necessity of a surgery was reached. Pet owners are encouraged to
seek second opinions if necessary or if in doubt about the appropriateness
of the selected treatment.
As cancer cells cannot
be seen with the naked eye chemotherapy or radiotherapy is a required
backup treatment. There are a number of risks with surgery, the
dogs age and health may be against him. Complications such as blood
clots, pneumonia and cardiovascular collapse can result. Cancer often causes a state of malnutrition
in the dog which may further compromise the ability of the dog to recover
from the trauma of surgery. Surgery is recommended for Mammary Tumours
(exception: inflammatory mammary cancer), Prostate Tumours, Oropharyngeal
Tumours, Skin Cancers, Gastrointestinal Tumours, Lung Tumours, Bone
Tumours.
Questions to ask before
the surgery
Before scheduling a surgery
for your pet, the following questions should be answered by both your pet's
medical team and your family.
1) What is the type, stage, and grade of cancer to be treated?
2) What are the expected effects of your pet's particular
tumor?
3) Is cure or significant health improvement achievable without
dramatically compromising your pet's quality of life?
4) Is surgery necessary or are there alternative, less invasive
treatments available?
5) What is expected in terms of post-operative care?
6) Can your family handle taking care of your pet's post-operative
needs? If your pet will require 24/7 care for the first few days, can
you take days off from work for the required period of time or have the
resources to leave your pet in the hospital for medical supervision?
Types of surgery
The type of surgery that
will be performed on your pet will largely depend on the anatomical site
of the tumor and the type, size and stage of the tumor. It can either
be performed as a single treatment or in combination with chemotherapy
or radiation to enhance the overall chance for cure.
Surgery for cure
This type of surgery will attempt to remove all traces of cancer
from your pet's body. It is generally believed that the first surgery
has the best chance of cure. The surgeon will not only remove the tumor
itself but also some of the surrounding tissues to make sure that no cancer
cells are left behind.
Lymph node removal
Lymph nodes are structures that drain lymphatic fluid for circulation
into the lymphatic system and is one of the
mechanisms by which tumor cells can spread to other organs. In some
cases, when the tumor cells were found to spread to the nearby lymph nodes,
it is desirable to remove the lymph nodes to prevent further spread of tumor
cells. However, there is still some controversy as to when such procedure
should be performed. Generally speaking, lymph nodes should be removed
if they are positive for cancer cells.
Palliative surgery
This type of surgery is not aimed to cure the pet but rather improve
the pet's quality of life by alleviating some of the painful symptoms
associated with the presence of cancer. It should be carefully considered
how the procedure's expected risks compare with expected benefit. If the
surgical treatment will result in worse outcome than no treatment at all,
other methods of palliative care should be applied such as pain management.
Debulking surgery
This type of surgery refers to the incomplete removal of a tumor.
It is usually performed to enhance the efficacy of other types of treatment
such as cryosurgery or radiation.
Miscellaneous surgical intervention in cancer management
Surgeons may also use their expertise in placing long term vascular
access catheters for delivering fluids, chemotherapy or anesthesia and
pain relief agents, placing of feeding tubes or performing emergency based
operations arising from infections, bowel obstruction, bleeding or intractable
pain.
Preventive surgery
Some types of cancer in pets can be prevented by surgical intervention.
For example, there is evidence that spaying of female dogs and neutering
of male dogs will reduce the risk of breast cancer and prostate/testicular
cancer, respectively. the removal of precancerous lesions from the skin
of white cats or removal of adenomatous polyps from the rectum of dogs may
also prevent subsequent cancer development.
Chemotherapy for Canine Cancer Treatment
Chemotherapy is likely
to be recommended for cancer that has already spread to other areas of
the body (metastatic disease), for tumours that occur at more than one
site (multicentric disease), or for tumours that cannot be removed surgically
(nonresectable disease).
The actual drugs used in chemotherapy protocols are given
in many different ways depending on the drug. Some are intravenous boluses
(injected all at once through an IV cathether) or directly into a tumour, some are diluted and given intravenously
(again through a catheter) and given over 1/2 to 4 hours, some are intramuscular
(into the muscle) or subcutaneous (under the skin) injections, some are
oral and sometimes "intracavitary" chemo is given where the diluted drug
is dripped into the cavity with the affected organ in it and then absorbed
into the body, and their are other routes as well. All of the routes are dictated
by the type of drug and the type of cancer/ protocol.
There are several chemotherapy
drugs that are used in combination to attack cancer cells and keep
them from multiplying. Cancers of the blood or those that spread are
excellent candidates for this type of treatment.
Some protocols are relatively
short in duration (ie: 16 weeks), or it can be much longer, (ie: 2 years)
depending on the type of cancer. The actual length of time will be up to
your oncologist. Treatments can be weekly (although this is usually for
a short period of time, ie: one month's worth of weekly treatments, decreasing
to every 3rd week by the 7th or 8th week) or sometimes they are biweekly,
every third week, every fourth week or some are even every 6, 9 or 12 weeks.
Wire-haired or non-shedding
pets may be particularly susceptible to chemotherapy. Certain breeds of dogs, will
experience variable amounts of hair loss. Hair loss often is most evident
on the face and tail, although some dogs will lose their "guard" hairs
a bit and some of the breeds with more "human" like hair (that continually
gets longer and longer, ie: poodles, lhasa apso's) will get a general thinning. The hair will regrow once chemotherapy
is stopped, but may have a change in colour or texture.
Some of types of cancer
where chemotherapy is recommended are lymphoma, mast cell tumours,mammary
tumours, hemangiosarcomas, soft tissue sarcomas, leukemias, multiple
myeloma, venereal tumours, osteosarcoma, gastrointestinal tract tumours,
skin and nasal carcinomas, brain and central nervous system tumours.
Most of the side effects of
chemo are controlled by oral medications. There are however, some dogs
that are supersensitive to all kinds or just one type of drug but they
are definitely a minority. The side effects are mostly gastrointestinal
(vomiting, diarrhea, nausea, lack of appetite) and low white blood cell
(infection fighting cells) counts. The reason that there are side effects
in these two "systems" in the body is because cancer cells are crazy, rapidly
dividing, nasty little cells and so far, there aren't any drugs that can
differentiate between the "bad" rapidly dividing cells and the "good, normal"
rapidly dividing cells. So when chemo is given, it is to wipe out the "bad"
cells, but some of the "good" cells get caught up in the mix. These "good"
rapidly dividing cells are found mainly in the bone marrow, where blood
cells are made and the gastrointestinal tract, where GI side
effects are seen.
The low white counts are usually
waited out. Most of the time the body just needs an extra bit of
time to recover, but sometimes antibiotics are used. For the drugs
that have the tendency to lower white counts, post chemo antibiotics are
given preventatively. ie: Doxorubicin treatments are always followed by
antibiotics for aproximately10 days . For the GI (gastrointestinal) side
effects, the dog can be pretreated with "anti" drugs before the treatment,
but most of the time your oncologist will wait and see and treat symptomatically.
Sometimes other side effects
from the drugs can be seen and that is because they can cause problems
with other organs...ie: kidney, liver, heart, etc. For the drugs that are
known to be toxic to these organs, a close eye is kept on the bloodwork
indicating that the organ is not tolerating the drug very well, or in the
case of cardiac side effects, these dogs recieve cardiac ultrasounds to
make sure things are looking okay. There is no way to know which animals
are going to have these other side effects, but once again, they are a minority.
Radiation for Canine Cancer Treatment
Radiation treatment
involves directing radiation directly at cells causing them to shrink.
It is used for tumours that are too difficult to remove by surgery or
if the dogs general health places him at risk from surgery. The higher
the dose of radiation that a tumour is exposed to, the better the chance
for destroying all of the tumour cells. Unfortunately high doses of radiation
compromises the normal tissue surrounding the tumour which is why
smaller treatment
doses of radiation are given 2x to 5x a week over a six week period.
Dogs receive anesthesia prior to treatment to ensure they do not move
when the radiation beam is being aimed at the tumour. Some cancers where
radiation therapy may be indicated are oral mycosis fungoides, squamous
cell carcinoma, Extranodal localized lymphoma, Mast cell tumours, Pituitary
macroadenoma, Epulis (acanthomatous, fibromatous), Nasal tumours, Adamantinoma,
Transmissable venereal tumours Perianal adenoma , Brain tumours
Cryotherapy for Canine Cancer Treatment
Cryosurgery (also called cryotherapy) involves
the controlled freezing of tissue to establish dying off of this tissue.
This happens because the blood supply to the tissue is destroyed. The sensory
nerves in the direct area are often destroyed as well, leading to a lack of
pain. It is a
technique that uses extremely cold temperature produced by substances like
liquid nitrogen, carbon dioxide or nitrous oxide to kill abnormal or cancer cells. These substances are administered
to the patient by using a gun-type apparatus with exchangeable tips to freeze
only the target tissue. It is usually used to treat relatively
small external tumors such as those on the skin. For treatment of easily accessible tumors
such as those in the anus, the pet will typically require only a local
anesthesia. Other sites such as the eyelid may require sedation and sites
such as oral cavity might require general anesthesia. For skin cancer, a freezing substance
can be applied to the tumour. This is often done with radiation to
ensure that all cells in the infected area are caught. Cryotherapy
can also be used after surgery to make sure that all mutant or cancerous
cells are removed.
How does cryosurgery
work?
The pet's hair will be first shaved near the area of the tumor to
be treated, followed by taking a sample for biopsy and removal of a majority
of the tumor to minimize the tumor volume for freezing and to shorten
the procedure time. The freezing of the tumor will be performed either
by spray or by a cryoprobe. The procedure duration can vary from 30 seconds
to a few minutes, depending on the site and the tumor type/size. The veterinarian
will typically also freeze a layer of normal cells surrounding the tumor
to make sure that no cancer cells are left behind.
The treatment itself can initially be painful. For this reason patients
are either anaesthetised, or perhaps sedated and treated with local anaesthetic.
After the first treatment follow up treatment is often not painful anymore.
Many patients require more than one session of cryosurgery, usually with
about one week in between. The frozen tissue may swell and change
color, occasionally oozing a small amount of blood or serum. It will form
a scab withing a few days and although the site may look infected, antibiotics
are not always necessary. After the treatment the tissue which
has been destroyed will slough off from several days or within 3 weeks, leaving a small
hairless spot.. This may
lead to some discharge. The wounds are normally not infected as the cryosurgery
also kills any bacteria present. However, your vet may prescribe antibiotics
if the treatment leads to large wounds.
What tumors are typically treated with cryosurgery?
While a variety of different tumor types have been treated with cryosurgery,
there are four specific tumor sites that have been treated with successful
results - eyelid tumors, perianal tumors, oral tumors and skin tumors.
Lesions which are commonly treated with cryosurgery, or tumours in
inaccessible places for conventional surgery, such as for instance in the
mouth or around the anus. It may also be used if a general anaesthetic is
considered to be too risky, for instance in elderly patients or those with
kidney- or liver disease.
Is it effective?
Some cases are totally cured with cryosurgery, such as small warts or
skin tumours. Other cases may be alleviated only, for instance by reducing
the size of a tumour or relieving pain.
Immunotherapy refers to
a variety of treatments that stimulate the body's own immune system to
either prevent or destroy cancer. For many years, it was believed that
the immune system was effective only in fighting infectious diseases caused
by invading agents such as bacteria and viruses. However, scientists have
recently discovered that the immune system also plays a role in protecting
the body against development of cancer and in fighting existing cancer. These
findings have led to the design of novel immunotherapeutic strategies which,
at this time, may be only available through clinical trials as experimental
therapies. These drugs
boost the immune system of your dog which hopefully, will trigger the
patients 'Cancer Recognition Response'. .These polysaccharide
compounds bind to surface receptors on the various Immune cells and
activate them. This means they either turn the cell on, or trigger the
production of more of that type of cell, or trigger the release of
certain chemicals (cytokines) such as a substance called Tumour Necrosis
Factor. The problem
is that even with a more effective immune system, there is no guarantee
that all cancer cells will be naturally destroyed. One of the main reasons
why combination therapy is used.
Cancer vaccines
The goal of cancer vaccines can be twofold. First, the vaccine can
be used to stimulate the pet's own immune system into destroying its existing
tumor, prevent cancer recurrence, or kill any cancer cells that may have
been left behind by previous treatments. Second, the vaccine can be used
to prevent or delay the development of cancer in healthy pets. Vaccines
that are used to treat cancers take advantage of the fact that certain molecules
on the surface of cancer cells are either unique or more abundant than
those found on healthy cells. These molecules can be used to stimulate the
immune system to make a specific immune response. Scientists hope that vaccines
containing these cancer-specific molecules will stimulate the pet's immune
system to attack cancer cells without harming normal cells.
Monoclonal antibodies
Monoclonal antibodies are special types of proteins made in the laboratory
that can locate and bind to molecules in the body and on the surface
of cancer cells. There are many kinds of monoclonal antibodies, each specific
to a particular molecule, and many of these have been approved for use
in humans.
Hyperthermia (also called
thermal therapy) refers to a technique that exposes tumors to high temperatures
(up to 113°F) in hopes of destroying the cancer cells. Its significance
became apparent in a number of human clinical trials that showed that
adding hyperthermia to radiation therapy resulted in a better outcome
than radiation therapy alone. Nevertheless, hyperthermia remains largely
an experimental treatment and may be only available through clinical trials.
Research into the use of hyperthermia for the clinical treatment
of cancer has indicated that it is lethal to cells, causes tumor regression,
increases the efficacy of radiation therapy and enhances the action of
many anticancer drugs.
There are a variety of methods and devices used for inducing hyperthermia.
In local hyperthermia, heat is applied to the tumor site using various
energy sources such as microwave, radiofrequency, or ultrasound. In order
to treat tumors that are located in or just below the skin, external applicators
are positioned around the appropriate region to focus the heat on the
tumor. In order to treat tumors that are located inside body cavities
such as the rectum, probes are placed inside the cavity and inserted into
the tumor.
In regional hyperthermia, various approaches may be used to heat
larger areas of tissue, such as an entire organ or a limb External applicators
are positioned around the body cavity or organ to be treated, and microwave
or radiofrequency energy is focused on the area to raise its temperature.
Local heating of tumors is typically accomplished by microwave radiation,
infrared radiation, radiofrequency or ultrasound. The need for specialized
equipment for administration of hyperthermia is a limiting factor for its
widespread use in veterinary medicine at this time.
Though cancer cells are
destroyed by hyperthermia treatment alone, many factors including the nature
and size of the tumor will influence the success of hyperthermia to eradicate
the entire disease. Populations of cancer cells that may escape the lethal
effects of hyperthermia are often resistant to subsequent heat exposure.
Therefore, as with other methods of treatment, hyperthermia is often used
in combination with radiation (see Treatment Combinations: Radiation and
Hyperthermia) or chemotherapy (see Treatment Combinations: Drugs and Hyperthermia)
to increase overall treatment efficacy. In canine cancer, treatment with
hyperthermia is more commonly administered in combination with radiation.
The effectiveness of hyperthermia
treatment is related to the temperature achieved during the treatment,
as well as the length of treatment and cell and tissue characteristics.
To ensure that the desired temperature is reached, but not exceeded, the
temperature of the tumor and surrounding tissue is monitored throughout
hyperthermia treatment.
Photodynamic Therapy
Photodynamic therapy (PDT)
is a treatment that uses a drug that preferentially travels to cancer
cells, called a
photosensitizer or photosensitizing agent, and a particular type
of light. When photosensitizers are exposed to a specific wavelength of
light, they produce a form of oxygen that kills the nearby cancer cells.
Selectivity of photodynamic therapy for certain cell types is accomplished
by either using photosensitizers that target only the specific cell type
or by exposing only certain cells to light after uptake of the photosensitizer.
Each photosensitizer is activated by light of a specific wavelength.
This wavelength determines how far the light can travel into the body.
Thus, doctors use specific photosensitizers and wavelengths of light to
treat different areas of the body with PDT.
In the first step of PDT, a photosensitizing agent is injected into
the bloodstream, which preferentially accumulates in cancer cells compared
to normal cells. The tumor is then exposed to light produced either by
a laser or other sources of light. The light will activate the present photosensitizer,
leading to the production of an active form of oxygen that destroys nearby
cancer cells. In
veterinary oncology, PDT has been used limitedly and usually in dogs with
localized, superficial, and minimally invasive tumors.
In addition to directly
killing cancer cells, PDT appears to shrink or destroy tumors in two other
ways. The photosensitizer can damage blood vessels in the tumor which will
prevent the tumor from receiving necessary nutrients. As a result, the starved
tumor will begin to shrink. In addition, PDT may stimulate the pet's immune
system to attack the tumor cells.
A previous limitation to widespread use of PDT was absence of data
pertaining to the safe use of photosensitizers in dogs. In the clinical
studies that have been conducted, however, there appear to be clear advantages
to the use of PDT over radiation therapy in regard to the number of treatment
sessions required to achieve therapeutic efficacy. Therapeutic limitations
to PDT include the inability of light to penetrate deeply into tumor tissue.
Therefore, treatment with PDT has been primarily aimed at superficial mucosal
cancers: those effecting the skin, lining of the bladder, and the lining
of the oral cavity. Research to develop new classes of photosensitizers
that are activated by longer wavelengths of light to allow deeper penetration
into tumors is currently underway.
One of the major complications
to the most common photosensitizer drug is the length of time that the
tissues of the body retain it. After administration of this photosensitizer,
the dog must remain in subdued light for 4-6 weeks to prevent damage to
the skin.
Gene Therapy
Gene therapy
is a relatively new science. In 1990, the first two approved gene therapy
trials were performed in the United States. Though both trials were unsuccessful,
it started a wave of research and clinical trials. In 1999, the death
of a young patient that was being treated for a liver enzyme deficiency
was a major setback however, just one year later, the first two successful
clinical trials using gene therapy were reported – one for SCID (severe
combined immunodeficiency, a.k.a. the “bubble boy” syndrome) and the other
for hemophilia B. Since then, there have been hundreds of clinical trials,
most focusing on cancer research. In veterinary medicine, only a few successful
gene therapy trials have been reported. For example: treatment of hemophilia
B in five dogs, restoration of vision in three briards with a hereditary
retinal disorder, and disease regression and prolonged survival in 12
dogs with malignant melanoma. In cats, gene therapy has been used to treat
genetic conditions such as mucopolysaccharidosis and lipoprotein lipase
deficiency. “Hereditary diseases of the eye are especially amenable for
gene therapy”, says Dr. Narfstrom. “I have treated a retinal disease of
dogs that have been blind since birth by using corrective gene therapy.
My plan is to also perform corrective therapy in Abyssinian cats when the
gene defect for PRA (progressive retinal atrophy) has been elucidated”.
The theory behind gene
therapy is to introduce foreign DNA into a cancer cell which when incorporated
into and expressed by that cell will usually facilitate that cells destruction.
There are primarily four approaches to gene therapy:
1) suicide gene therapy in which the protein product of that
gene changes an inactive drug into a toxic drug only in the cancer cell
carrying the foreign gene;
2) genetic immunotherapy in which the foreign gene causes
the cancer cells to express certain molecules on their surfaces that
will attract components of the immune system to attack and destroy the
cancer cells;
3) tumor suppressor gene therapy in which the foreign gene
replaces a mutated gene that has caused unregulated cell growth in the
cancer cells;
4) drug resistance gene therapy in which a foreign gene which
makes cells resistant to chemotherapy drugs is introduced into a patient's
normal cells so that the patient may be administered higher doses of
chemotherapy with reduced toxic side-effects.
Gene therapies utilize a number of methods, including viral and non-viral
vectors, to deliver genetic material into cells. As such, each of these
delivery systems has advantages and disadvantages, and to date is still
undergoing clinical evaluation for efficacy and safety issues.
Gene Therapy in Canine Cancer
Genetic immunotherapy has been the most explored form of gene therapy
for the treatment of dogs with cancer. In one study, dogs with malignant
melanoma, a very aggressive form of cancer, who were previously treated
with surgery and radiation treatment were treated with green-monkey kidney
cells expressing interleukin-2 (IL-2) DNA. Twelve months after treatment,
dogs treated with the genetic immunotherapy had a 37% survival rate compared
to a survival rate of only 6% in dogs that did not receive the genetic immunotherapy.
It is believed that the IL-2 expressing cells induced an inflammatory response
at the site of the cancer and facilitated an immune response that caused
an anti-tumor effect. In another study, when IL-2 gene therapy was combined
with a bacterial gene to enhance the immune effect in dogs with advanced
metastatic melanoma (lymph node metastasis), 45% of the dogs showed either
complete or partial remissions of tumors with significantly longer survival
times compared to untreated dogs. Additionally, no adverse side-effects
were observed in any of the dogs treated.
Genes can be transferred
either by introducing them directly into a patient’s cells (for example,
injecting into a tumor), or by removing cells from a patient (such as
bone marrow), introducing the gene, and then returning the cells back
to the patient. For the gene to be transferred successfully into the patient’s
cells, a vector (an agent or carrier) is required. Most gene therapy clinical
trials have used viruses as vectors for gene transfer. Viruses are ideal
vectors because they’re skillful at entering cells, traveling to the cell’s
nucleus, and “hijacking” the cell’s genetic material so it can make more
copies of its own genes. Viral vectors are currently the most efficient means
of transferring genetic material into a cell.
Despite the promise of
gene therapy, concerns about safety and efficacy remain, as relatively
little is known about the durability of the transferred genes, and the
practicality of repeated gene therapy treatments. There are also ethical
considerations. Although there have been few clinically applicable treatments
thus far, once the feline genome is completely mapped, the potential for
treatment of inherited and acquired genetic disorders is limitless.
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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.
