1400 Telegraph
Bloomfield Hills, MI 48302
248-334-6877-Phone number/248-334-6877-Fax Number

CANCER TREATMENT

Learning that your pet has a diagnosis of cancer can be overwhelming. We realize that your
pet is an important member of your family who deserves the best cancer treatment available.
Fortunately, continuous improvements in our knowledge as well as new and evolving
methods of treatment give many different treatment options to pets recently diagnosed with
cancer. Some cancers may be cured with appropriate treatment. Others, while they may not
be curable, can be treated while maintaining a good quality of life. For patients with
advanced cancer, treatment may help alleviate symptoms, such as pain, and greatly
improve the quality of the pet’s remaining life. Together, your oncology team will formulate a
treatment plan that fits your treatment goals while keeping your pet’s best interest in mind.
With this comprehensive approach to treatment and careful attention to quality of life, cancer
treatment can be a rewarding and healing experience.

What types of treatment are available?
A tumor biopsy is often required for your veterinary oncologist to give you an accurate
assessment regarding tumor type, grade (degree of malignancy) and surgical margins (if the
mass has been completely removed). Tumor staging is a process where additional
diagnostics may be recommended to determine if there is any tumor spread to other sites in
the body (metastasis). After reviewing biopsy and tumor staging results, your veterinary
oncologist can discuss various treatment options that are most appropriate for your pet.

Treatment options are categorized into local,
systemic, and multimodality therapies. Local
therapy
(surgery,
intralesional
chemotherapy,
cryosurgery, photodynamic therapy and radiation) is
best for cancer that is apparently confined to a well-
defined area in an accessible site. Systemic (whole
body) treatment consists of chemotherapy, gene
therapy,
anti-inflammatory
drugs
and
immunotherapy. These treatments are considered
for tumors that are widespread, or for tumors in
which there is significant and immediate risk of
spread from the initial location. In addition to the
above
mainstream
treatments,
nutrition
counselling and Complementary and Alternative Medicine (CAM) is a holistic approach
providing treatments (acupuncture, herbal/botanical medicine, nutraceuticals) designed to
treat all aspects of your pet’s health. Multimodality treatment involves therapies from more
than one treatment category (local, systemic, nutrition modifications, CAM), often providing
our cancer patients with the best possible outcome and quality of life.

Surgical treatment
Surgery is a common part of cancer treatment in which the pre-operative goal can range
from being a curative procedure to palliative (not curative, but improving overall quality of

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life). The type and extent of surgery along with possible complications is dependant upon
tumor type, location, grade and stage and will be discussed in further detail for individual
patients during your consultation. Your family veterinarian can perform some surgeries;
however, many cancer surgeries are more complex requiring
the expertise of a Board Certified veterinary surgeon.

Benign (non-invasive, non-spreading) tumors in well-defined
and accessible areas may be permanently cured by surgical
removal. Surgery is often the best treatment for the majority of
malignant cancers that have not yet spread (metastasized).
For malignant tumors, a wide margin of normal tissue
surrounding the cancer is removed to help decrease local
recurrence. Palliative surgical procedures may be
recommended for pets with advanced cancer to improve
quality of life. Post surgical recovery in most pets is rapid (1-
2 weeks) and post-surgical pain is controllable with
medications.

Small surgical procedures can be done under local anesthesia, however, general anesthesia
is required for most surgical procedures. General anesthesia is associated with very small
risk in otherwise healthy animals but the risk is greater in animals that are sick or elderly.

Special forms of surgery
The use of freezing temperatures (cryosurgery) can be used for some types of cancers.
Cryosurgery consists of rapidly freezing a tumor using liquid nitrogen and then allowing the
tumor to thaw slowly. Usually, two to three freeze-thaw cycles are performed during each
treatment. After cryosurgery, the tumor tissue slowly dies over the following two weeks.
During this time, redness, an unpleasant odor and appearance and bleeding may occur.
Success of this treatment is dependant upon tumor size (less than 1 cm) and invasiveness.
Cryosurgery may need to be repeated in 2-3 weeks.

Radiotherapy
Radiation is currently only available at referral veterinary hospitals. The mechanism of action
involves the use high energy radiation (similar to x-rays but at a much higher energy level)
that is capable of injuring cellular DNA (genetic material). Cells undergoing more frequent
cell divisions (multiplying) are the most sensitive to radiation and this is why tumor cells tend
to be more susceptible compared to normal tissue. However, normal healthy cells within the
radiation field can also be damaged or destroyed by the radiation, particularly actively
dividing cells like those of the intestinal lining, skin, bone marrow and immune system. The
damage to normal cells is the cause of radiation side effects. The side effects that may
occur for your pet secondary to radiation are dependant upon the recommended radiation
protocol and the tissue within the radiation field. These potential side effects will be
discussed during your consultation.

Radiation therapy is often used in combination with
surgery and/or chemotherapy. It may be used before
surgery to shrink very large tumors or after surgery
to kill cancer cells that may have remained. The goal
of treatment often determines the radiation
protocol (full course vs. palliative) recommended.
Full course radiation involves the administration of
small doses of radiation frequently (Monday through
Friday) for 15-22 treatments. This protocol is often
recommended for tumors in which the potential for
metastasis is low and radiation offers the potential

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for long term tumor control (over one year). Palliative radiation involves the administration
of large doses of radiation infrequently (once to twice a week) for 3-6 treatments. This
protocol is often recommended for high-grade tumors that have a high potential for tumor
spread or for palliation (pain relief, decreased bleeding, improved function and quality of life).

There are two main ways that radiation treatment is administered; external beam and
interstitial brachytherapy. Most radiation therapy in veterinary oncology is delivered as
external beam radiation where radiation is generated by a machine that is directed towards
the patient. Brachytherapy involves implanting a radioactive isotope inside the tumor.
Although, brachytherapy is less damaging to surrounding tissue compared to external beam
therapy, animals treated with radioactive implants do pose an exposure risk to their
handlers. The pet therefore has to be kept in a specially constructed compound until the
radioactivity is reduced to a safe level. Radiation therapy can only be administered to
animals under general anesthesia.

In both types the radiation dose needs to be carefully planned. A CT scan may be
recommended for radiation planning. Tumor types that may respond well to radiotherapy, or
where radiotherapy can improve quality of remaining life include mast cell tumors, sarcomas
(cancer of bone, muscle or various connective tissue), lymphosarcoma, and tumors of the
mouth, nose, brain and thyroid.

Systemic chemotherapy
Although we use many of the same chemotherapeutics as those used to treat people with
cancer, the side effects in our animal patients are much less severe than is traditionally
associated with chemotherapy in people. The reason for lower side effects is that veterinary
chemotherapy protocols use lower total doses and less aggressive combinations of drugs
than most human chemotherapy protocols. Therefore, most dogs and cats undergoing
chemotherapy have a normal quality of life.

In general, chemotherapy agents work by damaging cellular DNA of rapidly dividing cells.
Similar to radiation, normal healthy cells can also be damaged or destroyed by
chemotherapy, particularly actively dividing cells like those of the intestinal lining, bone
marrow and immune system. Resulting side effects such as vomiting, diarrhea, hair loss
and lowered resistance to infection can occur. In most cases, these effects can be
moderated or eliminated by use of appropriate medications and adjustment of the
chemotherapy protocol. Fortunately there are continuous improvements in the drugs
available for moderating side effects of chemotherapy. In general, the use of many drugs
together (drug cocktail) is less toxic and more likely to benefit the animal than use of a single
drug.

Chemotherapy is recommended for treatment of
various cancers such as lymphoma, leukemia, mast
cell tumors, hemangiosarcoma, osteosarcoma, high
grade sarcomas, and high grade carcinomas. It
may also be indicated for localized disease if
surgery or radiation therapy is not feasible. The aim
of chemotherapy varies from complete remission, or
prolonging the period of remission to palliative
therapy intended to minimize patient discomfort,
pain and suffering. Most cancers in veterinary
patients will not be permanently cured by
chemotherapy. In veterinary medicine chemotherapy
protocols have been designed to maximize the
patient’s life spans and most importantly their quality of life. These protocols are designed to
minimize side effects.

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Unfortunately, chemotherapy may not be effective in some patients. Treatment failure can
occur because chemotherapy can select for cells resistant to treatment (drug resistance) so
a drug may become less effective in subsequent treatment. When this occurs, attempting to
use higher doses of the same drugs may result in increased toxicity without an increase in
beneficial effects.

Anti-inflammatory drugs
Inflammation-promoting substances called ‘prostaglandins’ are produced by some tumors.
Treatment with non-steroidal anti-inflammatory drugs (NSAIDs) that reduce prostaglandin
production can therefore give some clinical relief. This treatment has caused remission of
some carcinomas in dogs. It is widely available and inexpensive. Patients have to be
monitored for signs of gastrointestinal tract and kidney problems.


Immunotherapy
An animal’s immune system may be capable of recognizing cancer cells as abnormal and
can respond by stimulating the production of special cells and factors that can destroy those
cancer cells. In most cancer patients, however, this immune response is typically weak or
absent. This is because cancer cells themselves reduce the ability of the immune system to
respond (immunosuppression). Therefore, methods directed at stimulating or enhancing the
immune system may be effective as an anti-cancer treatment.

Immunotherapy uses of the immune system to kill cancer cells. Various drugs (collectively
referred to as ‘immunomodulators’) can affect the immune system, by either suppressing or
enhancing it. A lot of current cancer research is aimed at investigating ways of stimulating
the immune system to specifically recognize cancer cells. An example of such treatment
involves the use of tumor vaccines which are administered to stimulate the immune system
to recognize malignant melanoma cells in dogs. In addition, there are a wide variety of non-
specific immunotherapy medications that target the entire immune system as a whole, not
necessarily to a specific cancer cell.

Future Prospects for Cancer Treatment

Gene therapy
Gene therapy is the introduction of part of the reproductive code (gene) into a cell. This type
of treatment has been used to target certain diseases including infections, inflammatory
disorders, and cancer. In order to get the new gene into a cancer cell, the gene needs to be
delivered by vectors, which include viruses, vaccines or physically in liposomes.
Mechanisms by which gene therapy is able to kill cancer cells include the delivery of “suicide
genes” making the tumor commit suicide, activating drugs to kill tumor cells specifically or
enhancing an immune system reaction to the tumor. Currently, in animals, this type of
therapy is still at the experimental stage.

Photodynamic therapy
Photodynamic therapy uses a photosensitizing drug that enters the tumor. The drug within
the tumor is activated by a specific wavelength of light to generate intracellular oxygen and
leads to death of cells and loss of blood supply. This type of treatment is useful for
superficial and bladder tumors but is not yet widely available.

Angiogenesis modulators
Cancers stimulate new blood vessels to grow. Angiogenesis modulators (or antiangiogenics)
are various drugs that reduce this new blood supply and “starve” the cancer. Some non-
steroidal anti-inflammatory drugs (see ‘Anti-inflammatory drugs’ above) are thought to have

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this anti-angiogenic effect. Other drugs, including a chronic low dose chemotherapy protocol
may also be anti-angiogenic.

Symptomatic and palliative treatment
Many of the above treatments, and others, may be used to palliate (relieve) the effects of the
cancer and improve quality of life. The potential side effects of treatment have to be
balanced against the improvement achievable and life expectancy.







Special diets are reported to delay cancer progression and
some may palliate the clinical effects of cancer or the side
effects of treatment.

Drugs that reduce pain and inflammation may also improve
the quality of life for your pet. Acupuncture may also be used
to control pain or improve energy levels, appetite and quality
of life in some patients.

As in humans, our understanding of cancer in dogs and cats is
increasing all the time. Survival rates are improving and many animals are alive and well as
“cancer survivors”.

In making decisions on the course of action to be undertaken in a specific situation, your
veterinary oncologist will help you come to an informed choice that takes into consideration
all factors. There are many treatment options available in the treatment of cancer, and there
is not one right answer for every pet or family. Your veterinarian will help you weigh the
pro’s and con’s of the various treatment options and will help you come to an informed
decision that is right for you and your pet.




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