Radiation Therapy for Dogs: How It Works and Common Side Effects

If you’re a pet parent facing your dog’s cancer diagnosis, you’ll want to know about the potential treatments for canine cancers, including radiation therapy for dogs. 

You may be dealing with a lot right now, both emotionally and financially. Read on to understand what radiation for dogs involves, how it works, and what you should expect so that you feel more prepared to make decisions for your dog.  

What Is Radiation Therapy for Dogs?

Radiation therapy for dogs is the use of high doses of radiation (beams of intense energy) to kill cancer cells. Radiation will damage the DNA of cancer cells, causing the cells to die.  

While canine radiation therapy is sometimes the sole treatment recommended for a cancer, it can also be used with other cancer treatments, such as chemotherapy or surgery. 

Radiation therapy is commonly recommended for treatment of canine cancers, but there are certain issues that limit pet parents’ access to it, such as: 

• Travel: Most veterinary clinics, including some specialty centers, are not set up to give radiation therapy. Significant travel with long-term hotel stays may be necessary, depending on the treatment plan. Treatment can last several weeks. 

• Cost: Most specialized cancer treatments are expensive, and radiation therapy is no different. More details will be shared later in the article. 

• Anesthesia: Radiation therapy requires anesthesia for each treatment. Some pet parents may hesitate to have their pet anesthetized as often as the plan calls for, and some pets may not be the best anesthetic candidates due to pre-existing disease. 

How Does Radiation Therapy for Dogs Work?

Before radiation therapy, a CT scan is usually recommended to check the full extent of the tumor. This allows for precise planning of your dog’s radiation therapy. Your pet will usually be anesthetized for the CT scan to ensure they don’t move. 

Pets undergo general anesthesia for each radiation session to allow the radiation to be given precisely to the cancer cells. Your pet will usually get small doses over several treatments (i.e. fractions), so multiple short anesthetic events are typically needed.  

Conventional fractionated radiation therapy involves splitting a dog’s complete dose of radiation over 15 to 21 treatment sessions. Stereotactic radiation therapy (SRT/SRS), on the other hand, uses higher doses of radiation to hit tumors with increased precision, requiring fewer treatments. 

As mentioned, radiation damages the DNA of cancer cells, killing these cells and affecting their ability to multiply.  

Why Would a Dog Need Radiation Therapy?

The goal of your dog’s radiation therapy depends on their individual case.  

Radiation may be recommended for: 

• Killing microscopic cancer cells left behind after a surgery 

• Shrinking a tumor to make surgical removal easier 

• Treating a tumor that can’t be reached surgically (e.g., some brain tumors, nasal tumors) 

In some cases, the overarching goal is to cure the cancer.  

In other cases, it may be to improve your dog’s quality of life for as long as possible, which is termed palliative treatment. This depends on the type, stage, aggressiveness, and location of your pet’s cancer, as well as their overall health. 

Side Effects and Risks of Radiation Therapy for Dogs

Side effects and risks are usually due to one of two things: the use of anesthesia and damage to noncancerous cells that are near the tumor.  

While deaths from anesthesia are possible, they occur in less than 1% of dog patients undergoing general anesthesia, according to one study. Your pet’s risk may be higher if they have an underlying health condition, such as heart disease or liver disease. The veterinarian will take precautions to reduce anesthetic risks.

With canine radiation treatments, damage to normal cells near the tumor is an expected side effect. Your dog’s individual symptoms will depend on the location and type of tumor being treated.  

Regardless of the treated location, the following are common radiation side effects in dogs: 

• Slow regrowth of any shaved hair 

• Loss of fur (alopecia) 

• Fur growing back a different color, often white 

• Sunburn-like lesions on skin in the treatment area 

• Darkened skin (hyperpigmentation) 

More serious side effects, which can occur months to years after radiation, include damage to the nerve tissue or bones. Generally, these unacceptable and irreversible side effects are avoided with precise planning for the cancer treatment. 

If the mouth is treated, your dog is likely to develop irritation and sores within the mouth. You may notice excessive salivation (drooling), bad breath, and difficulty eating.  

Treatment of nasal tumors can result in nasal discharge and post-nasal drip. 

If the eye is near a treatment site, you may notice inflammation (swelling) in their eyelids, conjunctiva (membrane on inner eye), or cornea (clear layer in the front of the eye). Other risks include the development of dry eye, corneal ulcers, cataracts, or vision loss. 

Dogs may develop diarrhea, sometimes with blood, if the intestines are within the treated field.  

Your veterinarian should discuss what side effects are likely for your dog based on the treatment area. The risk of side effects varies by cancer type and location. Generally, around 25–50% of dogs develop some side effects from radiation therapy. 

Benefits of Radiation Therapy for Dogs

Radiation therapy is an effective, localized treatment for tumors. It can help kill microscopic cells left behind after a surgical procedure, with the intent to cure the patient of cancer.  

In some cases, radiation therapy can shrink a visible tumor so that it can be surgically removed. 

If the cancer cannot be successfully treated or surgically removed, radiation therapy can offer a treatment that improves patient quality of life and may increase lifespan. Results are sometimes seen within the first few days after treatment begins. 

Effectiveness of Radiation Therapy for Dogs

In one 2016 study, the overall tumor response rate to palliative radiation was around 75%. However, the effectiveness of a treatment will depend on the type of radiation therapy pursued, whether the pet has had other treatments, the type and aggressiveness of the cancer, and the tumor’s location. 

Quality of life for dogs after radiation is usually good, but each case is unique. Your pet’s oncologist will be your best source for considering your pet’s potential response to radiation therapy. 

Cost of Radiation Therapy for Dogs

Radiation therapy costs range from $3,000 to more than $13,000. 

This large range is due to variation in the treatment plans for different types of cancer, as well as geographic location. Your costs will be higher if your dog needs more treatments or if your dog has other health conditions that complicate treatment. 

If you decide to pursue radiation therapy but are concerned about cost, consider the following suggestions: 

• Accident and illness insurance plans may cover part of your dog’s cancer treatment if the condition is not pre-existing or is excluded. 

• CareCredit, a type of credit card, may help you finance your dog’s cancer treatment. 

• Clinical trials may be available for your dog’s cancer, which may reduce the cost. 

• Some nonprofits help cover the cost of cancer treatment in dogs. 

• Crowdsourced fundraising may help you get funds for your pet. 

Preparation for Radiation Therapy for Dogs

You will generally be asked to withhold food and water from your pet for a certain amount of time before each radiation treatment.  

Commonly, food is withheld after midnight and water is withheld for several hours. Your veterinarian should give you specific instructions on withholding food and water.  

Keep in mind that significant travel may be needed for your dog to get radiation therapy. If your dog has anxiety while traveling, speak with your veterinarian about anti-anxiety treatments, such as trazodone.  

Make sure you also ask your veterinarian for instructions about any medications you’re giving your pet. Some medications, such as thyroid or cardiac medications, are usually still given the morning of an anesthetic procedure, while others, such as blood pressure drugs or non-steroidal anti-inflammatories (NSAIDs), are generally not given.  

However, because anesthesia is given frequently to dogs undergoing radiation, instructions may vary. Again, closely follow your veterinarian’s instructions.  

Care and Recovery for Radiation Therapy for Dogs

Keep in mind that most dogs get multiple doses of radiation. While some treatment plans may only last a few days, others may last several weeks.

It's possible you’ll need to stay in a hotel if you live too far away to travel to the clinic daily. Bring along a comfortable bed for your dog to rest and recover in, such as this ATIFBOP orthopedic bed or this FurHaven Velvet Waves option. 

Most short-term effects occur in the skin or mucous membranes, like within the mouth or the intestines.

If your dog is in pain from these side effects, speak with your oncologist.

They may prescribe additional medications, such as carprofen or gabapentin, to help with your dog’s pain. Anti-nausea medications like Cerenia can also help some pets. 

If your dog is also undergoing chemotherapy, the veterinarian may give instructions for handling feces and urine. 

Long-term effects of radiation can develop months to years later. You should expect that the veterinarian will want follow-up appointments to watch for recurrence of cancer or the development of long-term side effects. 

Alternatives to Radiation Therapy for Dogs 

Some pet parents choose not to get radiation therapy for their pets. Your veterinarian may also offer chemotherapy or surgery, either instead of radiation or with limited radiation.  

If radiation therapy is not a good choice for you, it’s okay to discuss other options with your veterinarian. You can also discuss whether shorter courses of radiation could improve your pet’s comfort. 

Outside of radiation, chemotherapy, and surgery, your veterinarian can also recommend other forms of palliative care to help improve your pet’s comfort. Though it will not necessarily increase length of life, it’s important that your pet is comfortable.  

Treatments may include: 

• Pain medications like carprofen, buprenorphine, or gabapentin 

• Appetite stimulants like mirtazapine or Entyce 

• Anti-nausea medications like Cerenia 

• Anti-anxiety medications like trazodone 

• Nutrition counseling 

• Physical rehabilitation