Download Radiation Therapy Information Sheet

PORTLAND VETERINARY ONCOLOGY CENTER
13655 SW Jenkins Road
Beaverton, OR 97005
Phone: (503) 644-6581 Fax: (503) 626-8184
Dr. Juliana Cyman
Diplomate ACVR (Radiation Oncology)
www.portvetonc.com
Radiation Therapy Information Sheet
Portland Veterinary Oncology Center is a veterinary hospital specializing in radiation therapy and
chemotherapy. The aim of the clinic is to provide compassionate, appropriate, and advanced treatment
options for pets with cancer. It is one of a few veterinary facilities in the country equipped with a linear
accelerator with electrons (a type of radiation machine). This machine allows for tumors in certain locations
to be treated more effectively. In addition, for more complex treatment plans, computer generated treatment
planning is available. Dr. Cyman, who operates the facility, is a board certified veterinary radiation
oncologist, of which there are only 50 in the country.
What is radiation therapy?
Radiation therapy is the practice of using high energy waves or particles to treat disease. The
energies used for cancer treatment are generally much higher than those used for x-ray exams. For external
beam therapy (which is the type of radiation treatment being considered for your pet) sophisticated
equipment is used to produce and direct the radiation at the tumor area. Patients receiving external beam
radiation therapy do not themselves become radioactive and therefore do not pose any danger of exposure to
others.
How does radiation therapy work?
Radiation can kill cells or damage them so they cannot reproduce. This includes tumor cells as well
as normal cells of other tissues. However, because many tumor cells are rapidly dividing, they are often
more sensitive to the effects of radiation compared to many normal cells. In addition, normal cells are
usually more efficient at repairing damage from radiation than tumor cells. The goal of radiation therapy is
to utilize these differences to destroy the tumor while minimizing damage to the normal tissues that will be
included in the radiation treatment field.
When is radiation therapy used?
Radiation can be used by itself; however it is more commonly combined with surgery and or
chemotherapy. It may be given before surgery to shrink the tumor or after surgery to stop the growth of
remaining cancer cells. The combination of treatments recommended and the sequencing of these will
depend on the tumor type, the size and location of the tumor, possible side effects, as well as many other
factors.
How successful is radiation therapy?
Several variables influence each patient’s prognosis, such as the type and grade of the tumor, the
stage and location of the cancer, and the overall health of your pet. Although cancer can be unpredictable,
the anticipated outcome following a course of radiation will be discussed with you.
What is the radiation treatment schedule?
The number of treatments recommended and the scheduling of them is determined on an individual
basis. In general, giving many small doses increases the chances for tumor control while decreasing the
likelihood for normal-tissue side effects. Therefore, most patients have 15-20 treatments over 3-7 weeks.
The treatments are given Monday through Friday or Monday, Wednesday and Friday. The pros and cons of
each schedule will be discussed with you prior to beginning the therapy. It is very important to carefully
choose the appropriate radiation protocol because a course of radiation therapy can be safely delivered only
once to the same treatment field. Radiation therapy may also be used when the aim is not to cure but to
improve the patient’s quality of life. This is called palliative care. Just a few treatments (usually 3-6) will
often relieve pain, shrink the tumor, and reduce pressure, bleeding or other symptoms of cancer.
A short acting anesthetic is given to immobilize the patients for their treatments. Therefore, your pet
will need to be fasted 8 hours prior to the treatment from food and water. Although anesthesia always
carries some risk, the risk is usually minimal due to safer anesthetic agents, lower doses, monitoring
equipment and short anesthesia times.
What are the costs involved with radiation therapy?
Radiation therapy for veterinary patients can be costly as it requires very complex equipment,
expensive anesthetics, and the services of many health care professionals. Fees vary depending on the
number of treatments, the complexity of the treatment planning involved and the number of fields of
radiation. A written estimate of fees will be provided at the time of consultation.
What are the potential side effects?
The possibility of adverse side effects is a major concern for many clients when seeking cancer therapy
for their pet. Although there are some side effects associated with cancer treatment in pets, they are
generally much less frequent and less severe than most people anticipate. Pets very rarely experience
nausea, vomiting, diarrhea or inappetance. With radiation therapy, the side effects usually resolve quickly,
are severe in few patients, and are limited only to the tissues in the irradiated treatment field (which includes
the tumor and a margin of normal tissue around it).
o Skin – Potential side effects to the skin include localized hair loss, hypo-or hyper-pigmentation,
and temporary moist or dry dermatitis. Most pets will experience some or all of these effects,
however they will occur only in the irradiated field. The extent of these effects depends mainly on
the amount of tissue treated, the radiation protocol used, individual patient sensitivity, and the
ability to prevent the patient from traumatizing the area. Hair loss is usually temporary in cats, but
it may be permanent in dogs (again, only in the treatment field). Hair will take months to re-grow
and it may come back in a different color. Moist dermatitis (reddened, weepy skin) usually begins
3-4 weeks after the onset of radiation therapy. Because it is often accompanied by itchiness,
protective methods including use of shorts, T-shirts, patted bandages on the paws, or and
Elizabethan collar may be needed to prevent self-trauma. It is very important to prevent your pet
from scratching, licking or chewing at the irradiated area as the skin in the field is easily injured.
You may gently clean the skin with warm water and a wash cloth. In addition, topical or oral
medications may be dispensed if necessary. The affected area usually heals 2-3 weeks after
radiation ends. Bathing and swimming are not recommended until the skin is healed.
o Mouth – You may notice increased salivation and some tenderness in the mouth if the tumor was
located in the oral cavity, nose or throat. Therefore, some extra pampering and feeding soft, low
salt food may be helpful. We also may dispense a medicated wash or recommend a dilute tea rinse.
Inappetance occurs rarely, however it is more likely to affect cats and small dogs. If necessary, a
gastrostomy (stomach) tube may be placed to ensure adequate nutritional intake. These effects
should subside within 1-2 weeks following the end of radiation therapy.
o Nose – If the nose is in the treatment field, sneezing and nasal discharge are common. However, if
your pet is experiencing bloody nasal discharge from a nasal tumor, the bleeding should actually
subside within 2 weeks of starting radiation.
o Eyes – The eyes are excluded from the treatment field if at all possible. However, sometimes the
location of the tumor, such as those of the nasal cavity, requires partial or total inclusion of the eyes
into the field. You may notice during and shortly after radiation therapy a reddening of the eyes,
and discharge from the eyes. Eye drops or ointments may therefore be prescribed. It is imperative
that your pet does not rub or scratch at their face or eyes as this may delay healing or injure the
cornea. If your pet should start to squint, please bring it to my attention immediately as this may
indicate the development of a corneal ulcer, which needs to be treated and monitored closely.
Reduced tear production can occur and may be permanent requiring daily treatment with eye
wetting agents or other medications. Other effects that may develop months to years after radiation
include cataracts and changes in the retina. Visual impairment may result, but rarely leads to
complete blindness.
o Bones and joints – The bones in the irradiated field can be weakened and also more susceptible to
infection. This is usually not a concern except when the field includes bones of the mouth, or in
bones already weakened by tumor (such as with osteosarcoma). It is important to prevent trauma
and the possibility of secondary infections to these irradiated bones. For example, patients who
have had bones of the mouth irradiated have special needs when it comes to dental procedures and
playtime. Please contact Dr. Cyman prior to any scheduled dental work so she can inform your
veterinarian of these special needs. In addition, these patients should not play tug of war, chew on
hard objects or catch hard Frisbees. Arthritis or fibrosis may result if the radiation field is over a
joint; however, this rarely becomes clinically apparent.
o Brain – The brain is rarely in the field except when treating brain, inner ear or nasal tumors. The
most common side effects start 2 weeks to 3 months after treatment and usually last for 2-3 weeks.
These effects include lethargy and sometimes with brain tumors, temporary recurrence of the
original neurological abnormalities. Cortocosteroids (prednisone or dexamethasone) may be
prescribed to alleviate symptoms.