HOW TO Understand Radiation Therapy for Dogs

Radiation therapy is used to kill a growing tumor and can treat larger areas that a veterinary surgeon cannot remove. It is typically only used on the part of the dog’s body that has been affected by cancer.

According to Flint Animal Cancer Center at Colorado State University, “Radiation therapy and surgery are the only modalities that can locally control solid tumors such as carcinomas and sarcomas. Radiation therapy can also be used to provide relief of pain, or improve function in patients suffering from advanced cancers.”

How Does Radiation Therapy for Dogs Work?

Radiation therapy is used to annihilate a cancerous tumor. It kills cells by releasing ionized radiation directly to the dog’s DNA, which damages it through the formation of oxygen free radicals. The cells then die off after they begin to divide.

“Cancer cells develop because of damage to DNA. This substance is in every cell and directs all activities. Most of the time when DNA becomes damaged, the body is able to repair it. In cancer cells, the damaged DNA is not repaired. Dogs can inherit damaged DNA, which accounts for inherited cancers. More often, though, a dog’s DNA becomes damaged by exposure to something in the environment, like smoke, pesticides or other carcinogens,” writes CanineCancer.com.

Radiation therapy wipes out cancer cells as they are dividing, which they are constantly doing.

PetEducation.com says, “Using radiation therapy, beams of photons, electrons or gamma rays are focused on the tumor. When the photon, electron or wave hits the nucleus of a cell, it alters it, destroying the ability of the cell to divide and grow. The slower growth rate and ultimate death of the cancer cells causes the tumor to shrink over time. Radiation affects both normal and cancer cells, but the radiation treatment is designed to produce the maximum effect on the tumor and minimize the effect on normal tissue.”

What is the Difference Between Radiation Therapy and Chemotherapy?

Chemotherapy is used to treat the entire body and focuses on tumors that have metastasized (spread to other parts of the body). It cannot control the growth of tumors, and in most cases, it will not cure them, either. Radiation therapy not only has the capacity to diminish the size of the tumor, it can also cure some cancers.

“Chemotherapy is often prescribed for cancers that have spread to several areas of the body. Chemotherapy uses drugs to kill cancer cells while radiation uses specially calibrated X-rays to target cancer tissues. Chemotherapy is different from radiation in that it typically is not a course for curing cancer,” states VetInfo.com.

What Are the Most Common Tumors Treated with Radiation Therapy?

These are the most common tumors treated with radiation, according to Flint Animal Cancer Center:

Brain tumors
Pituitary tumors
Tumors of the body and extremities (soft tissue sarcomas, mast cell tumors, vaccine-associated sarcomas)
Lymphoma
Nasal tumors
Oral tumors
Bladder tumors
Prostate tumors
Perianal tumors
Bone tumors

What Are the Types of Radiation Therapy?

There are few types of radiation therapy. Some utilize radioactive particles that can be injected into the body. Others use iodine, which collects in the thyroid gland, and is primarily used to treat thyroid diseases, like hyperthyroidism.

According to PetEducation.com, the following types of radiation therapy are the most commonly used:

“‘Brachytherapy’ is the term used to describe the radiation therapy that is administered through radioactive implants. Implants of iridium-192 are the most commonly used. Radioactive wire containing iridium-192 can be placed using a large needle, or through minor surgery.”
“Beams of radiation are the type of therapy most people are familiar with. A linear accelerator can be programmed to produce varying levels of photon or electron beams that are focused on a certain area on or within the body. These beams, or waves, are focused on the tumor, and when the actual burst of radiation therapy is over, no radioactivity remains in the body.”

How Is Radiation Therapy Administered?

Your dog will need to be anesthetized because he cannot move during the procedure.

“Using radiographs (X-rays), MRIs and CAT scans, the exact location of the tumor is located. Using mathematical formulas and mapping techniques, the machine is programmed and positioned to focus the beam on the tumor. Various points on the animal’s skin may be marked to provide ‘landmarks’ for subsequent treatments. This machine setup usually requires 30-60 minutes. The actual treatment time during the following sessions is very short, and the animal is usually anesthetized for only 10-15 minutes,” says PetEducation.com.

Radiation therapy is normally given in small dosages over the course of 2 to 5 weeks. The number of treatments your dog need depends on the type, size and location of your dog’s cancer and his health.

What Are the Side Effects of Radiation Therapy?

Side effects of radiation therapy are either acute (severe) or chronic. They also depend on the dose of radiation, but your dog will most likely experience nausea, bleeding problems and a compromised immune system. There may also be some skin issues, which will look like a sunburn. Some dogs lose their fur, but it usually grows back.

PetEducation.com says, “Acute injuries begin during or shortly after the completion of therapy. They arise in tissues within the radiation therapy field that are growing and dividing rapidly. Chronic side effects arise from damage to tissues that slowly replace old, dying or damaged cells (i.e., bone, retina [or] brain). Because these cells reproduce slowly, it takes a longer period of time for them to be replaced.”

However, newer radiation technology is designed to limit the side effects.

“Pets who are likely to develop significant side effects will often require pain medications or anti-inflammatory medications. Your oncologist, radiation oncologist and regular veterinarian will work as a team to keep your pet as comfortable as possible,” writes Veterinary Cancer Center.

Unfortunately, your dog may develop long-term or permanent side effects from radiation therapy.

“Often there can also be a risk of a long-term, permanent side effect from radiation. Fortunately these side effects are rare and your oncologist and radiation oncologist will discuss these with you before starting treatment,” says vcchope.com.

You can also give your dog a supplement containing reishi mushroom. Not only will your dog’s immune system get a healthy boost, but providing your dog with reishi during treatment will help reduce the side effects of radiation, as well as minimize his risk of infection, help with fatigue and reduce the loss of appetite and fur. It will help to reduce his stress, and relieve any pain he may be experiencing. He will also be getting a healthy dose of antioxidants to fight off free radicals, which damage the body.

Find A Vet HOW TO articles are intended for informational purposes only. You should always consult with your veterinarian about any health issues affecting your dog.

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