Radiation therapy is an effective way to treat many kinds of cancer in almost any part of the body.  Many veterinary patients are treated very effectively with radiation therapy for their cancers.  Radiation may be given alone or in combination with other forms of treatment such as surgery or chemotherapy.

Sample of a part of a three-dimensional CT based treatment plan used in the radiation planning process.  This type of planning increases the accuracy and decreases the side effects of radiation.

 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.  Special equipment is used to produce and aim the radiation at the tumor area.  The most common type of machine used today in human radiation therapy is called a linear accelerator.  This is the type of radiation therapy used at the Animal Cancer & Imaging Center.

 How does radiation therapy work?

   Radiation kills cells by disrupting the DNA of the cell. Radiation can kill cells or keep them from growing and dividing.  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 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 try to utilize these differences to destroy the tumor while minimizing damage to the normal tissues that will be included in the radiation treatment field. Like surgery, radiation therapy is a localized treatment, affecting only the area included in the radiation treatment field.

When is radiation therapy used?

       Radiation therapy can be used by itself, however, it is more commonly combined with surgery and/or chemotherapy.  It may be given before surgery to shrink a tumor to a more operable size, or after surgery to stop the growth of any remaining cancer cells that the surgeon was not able to remove. 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 that we will discuss with you.

   Radiation therapy may also be used for the purpose of pain relief when it is known that the cancer cannot be effectively treated by surgery, chemotherapy, or a full course of radiation therapy.  This is known as “palliative” radiation.  Just a few treatments (usually 3-6) will often relieve pain, shrink the tumor, and reduce pressure, bleeding or other symptoms of cancer.

 What is the radiation treatment schedule?

   The number of treatments recommended and the scheduling of those treatments are 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.  The treatments are typically given daily, on a Monday through Friday basis.  Your pet can be treated as an outpatient, remain in the hospital for the entire treatment course, go home on weekends, or any combination of the above.  For outpatients, you may accompany your pet to each treatment and take your pet home soon after treatment, or patients can be dropped off in the morning and picked up later in the afternoon.

What happens at each treatment appointment?

   Prior to each treatment, an 8 hour fast is required.  Your pet will receive a thorough physical examination at each treatment visit.  It is important that you notify the doctor or the radiation therapist of any changes in your pet’s condition (e.g. vomiting, diarrhea, lethargy, etc.).  Your pet is put under a brief gas anesthesia. Total anesthesia time is usually less than 15 minutes.  The actual treatment time when the radiation is being delivered is only about 2 minutes, but set-up prior to the actual treatment takes several minutes.  If you bring your pet in for the treatments, they will usually be able to go home within 30-45 minutes.  Although anesthesia carries some risk, the risk is usually minimal due to safer agents, lower doses, and short anesthesia times.  If the doctor feels that your pet has a higher risk for anesthesia due to some other medical problems, you will be informed of that risk.

 What are costs involved with radiation therapy?

    Treatment of cancer with radiation can be costly due to the very complex equipment and the services of many health care professionals including the veterinary oncologist, the radiation therapist, the radiation physicist, and the veterinary radiation therapy technician.  Our CT based computer treatment planning is done by Dr. Sue LaRue, Diplomate, ACVS, and ACVR (Radiation Oncology), of the Colorado State University Radiation Oncology Service.  Costs for the treatment planning vary depending on the complexity of the treatment plan and the additional services required by CSU during the treatment course.  Dr. LaRue monitors each patient closely, reviewing calculations and positioning, etc. during the course of therapy.

CSU has recently purchased a state of the art 3-D planner.  The new equipment enables us to offer custom blocking to the computer planned patients. Custom blocking further increases our accuracy of treating the tumor and increases our ability to spare normal tissues near the treatment field.  The cost of treatment planning ranges from $600-$900. 

  Each treatment, including exam and anesthesia fees, is $185.  Typically 15-22 treatments are done.  Therefore, planning and treatment costs range from $3,375 (15 fractions plus $600 planning fee) to $4970 (22 fractions plus $900 planning fee) for more complex cases.  Palliative courses of therapy (3-6 treatments) are typically $225 per fraction.  Fees can vary depending on individual patient needs and will be thoroughly discussed prior to treatment.  Charges for hospitalization are separate from the radiation therapy charges and will be discussed if you plan to hospitalize your pet during radiation therapy.  A written estimate of fees will be provided for you prior to beginning therapy.  Additional radiographs called “port films” may be necessary during the course of radiation therapy and are $60 each.  Typically 2-3 port films are required during the course of treatment.  Some types of cancer, such as certain soft tissue sarcomas or mast cell tumors on the limbs may not require port films. 

What are the side effects of treatment?

  Side effects of treatment in general fall into two categories:  acute and late effects.  Acute effects typically start towards the middle to end of the treatment course and can continue for several weeks after.  These usually affect skin and mucous membranes in the radiation field. Late effects are those that can occur months to years after radiation and are dependent on the tissue in the radiation field.  Systemic side effects are generally not seen.  ACIC has prepared a presentation available on CD that discusses these effects in detail and shows pictures of what to expect.  The CD’s are available upon request.

Hair color changes and hyperpigmentation of the skin in the irradiated field are not uncommon.  This patient was successfully treated with radiation therapy for a mast cell tumor that was inoperable.