Radiation treatment for dog brain tumors: A personal experience

If you read our previous post, you know about the steady decline and worsening symptoms that led to our Boston Terrier, Jack’s canine brain tumor diagnosis. Once the neurologist showed us the MRI results in February 2018, we knew things were bad. The size and position of his brain tumor were clear, and with a cystic meningioma diagnosis, the clock was ticking.

Jack could barely stand without falling over, his appetite was gone, and he had already lost 25% of his body weight. Multiple veterinarians gave him about one month to live. We definitely wanted to do something to prolong his life, but we had to do it quick. What lay ahead was a ton of research, many decisions to make, and lots of doctors’ visits … all in a very short amount of time.

What to do when your dog has a brain tumor
When a dog gets a terminal cancer diagnosis, there are several medical courses of action you can take. And the decision you end up going with can be highly personal and dependent many factors. We aren’t doctors, but we did navigate the often confusing journey that dog owners have to take when presented with a cancer diagnosis. The following were the medical options presented to us (as we understood them) for a canine brain tumor:

  1. Surgery — where tumor is physically cut out and removed. In our case, this was not an option, given how deep inside the brain Jack’s tumor was. Doctors could not reach the cancerous growth without doing significant damage to the rest of the brain. Getting a biopsy of the tumor was not even an option in Jack’s case. While not good for us, surgery is a viable option for many, especially if the tumor is clearly defined, easily accessible, and has not metastasized (or spread) throughout the body.
  2. Chemotherapy — where the patient is administered a drug (typically orally or through an injection) that attacks the cells in cancerous tumors, hopefully killing them off without damaging other parts of the body. Chemotherapy is often used to treat cancer that has spread, or metastasized throughout the body. In our case, chemotherapy was not an option due to the fact that most chemo drugs are ineffective on cystic meningiomas, as many cannot cross the blood-brain barrier.
  3. Radiation therapy — where powerful X-rays are focused on a tumor, damaging the DNA in the cancerous mass. While radiation doesn’t kill the tumor cells right away, when those damaged cells attempt to divide and grow, they will die. Because Jack’s tumor was deep within his brain and couldn’t be treated by other methods, this was a good option for us.
  4. Palliative care — where the symptoms of the tumor are treated, but no effort is made to remove or stop the tumor from growing. Palliative care would include the administering steroids and anti-convulsant drugs in an effort to make the dog more comfortable, but will not result in the cancer going away. So in effect, while drugs like the steroid prednisone might reduce the swelling in the brain (AKA edema), thus minimizing pain and suffering, it will not shrink the the tumor itself. On prednisone alone, the doctors gave Jack only 30 days to live, so we wanted to go above and beyond palliative-only treatments.

After learning about the options, we chose to pursue radiation therapy because Jack, while 13 years old, was in good health otherwise. We didn’t think he was ready to go, and we certainly wanted to have him around for as long as possible as long as his quality of life was good.

Radiation therapy

So from there it was off to talk to a radiation oncologist in Austin, who spent about an hour going over how radiation works and some of the risks involved with the procedure. We also talked about the many different types of radiation therapies available.

Radiation treatment works by delivering a predetermined dosage of radiation to the tumor or tumors. A CT scan must be performed before any radiation is delivered to map the location of the tumor so the radiation oncologist knows where to direct the x-ray beam.

Types of radiation treatments available have names such as IMRT (intensity-modulated radiation therapy), SRS (stereotactic radiation surgery), SRT (stereotactic radiation therapy), and “conventional” radiation therapy. You might also see brand names such as CyberKnife and TrueBeam.

The differences between these technologies can be a bit confusing at times. Regardless of the specifics, the main differences we found between treatments are the number of treatments required and the precision / accuracy of the radiation dosage delivered to the tumor. The type of treatment that’s best for your dog might be a determining factor in which vet you go with, as the machines are very expensive and some vets don’t have access to the latest technology.

Besides dosage, one of the main concepts to understand is “fractionation.” To improve the safety of the radiotherapy, the radiation dosage is often divided up, or “fractionated” across multiple treatments. So instead of 1 single treatment session, the patient might go in 3, 5, or even 20 or more times.

Based on our research, the number of treatments required is highly dependent on how precisely the machine can deliver the radiation and how much risk you are willing to take. Here’s a quick rundown on how everything was explained to us.

Conventional radiation therapy
Conventional radiation therapy was explained to us as having the accuracy of a shotgun. While the beam used will definitely hit the tumor, it will also hit surrounding healthy tissues as well. As a result, the dosage of radiation needs to be delivered in small fractions so that healthy tissues have time to recover between treatments. And because “normal” non-cancerous cells are more adept at repairing themselves than tumor cells, eventually most of tumor will die off and shrink.

With conventional radiation therapy, we were told Jack would need more than 20 treatments, doled out over the course of a month. This would keep the risk of side effects very low. Here’s the problem though … your dog will need to be anesthetized for every treatment, which can be stressful and hard on their health. And with Jack having a heart murmur, we definitely didn’t want him to go under that many times. Also, with Jack’s estimated 30 days to live, we didn’t really have the time to do 20 treatments.

Newer radiotherapy technologies (SRT, IMRT, SRS, TrueBeam, Cyberknife, etc)
SRT, IMRT, and Truebeam are all newer, much more accurate technologies than conventional radiation. Doctors said that if the beam used in conventional radiation is a shotgun, these technologies produce a focused beam more akin to a rifle, capable of much more accurately hitting the target. Some of these technologies boast millimeter accuracy.

As a result of the improved accuracy that come with treatments like stereotactic radiation therapy, radiation oncologists are capable of delivering the radiation dosage in fewer sessions, while keeping the risk of damaging healthy tissues low (although some radiation oncologists still advise going with 20 sessions to reduce risk even further). In our case, Jack received SRT treatment from a TrueBeam machine, in 5 fractions. Our radiation oncologist determined this would be the best balance for us given the characteristics and location of the tumor, and us not wanting Jack to be subjected to anesthesia too often.

This is the TrueBeam machine used to treat Jack’s brain tumor. It looks a bit like a robot from a science-fiction movie. Notice that the device (like many others used in radiotherapy) rotates around the patient to deliver radiation from multiple angles to more effectively target tumors or reduce the risk of damaging surrounding tissues. Also note that this treatment was first used on humans, then more recently, veterinarians started using them.

Risks of radiation
With any medical procedure, there are risks. And radiation therapy is no different. In Jack’s case, because the tumor was right next to the optic chiasm (which controls vision), we were told that one of the main things that could go wrong would be loss of vision, or total blindness. And while the chances of this happening were less than 1% with 20 fractions of traditional radiation, reducing the number of treatments to 5 more powerful fractions using an SRT machine raised the chances to 5%.

Additionally, radiation therapy is not a guaranteed cure for cancer. More than likely, some tumor cells will survive the radiation and might grow back over time. In other words, radiation is great at halting the growth of a tumor or even shrinking it, but the cancer might come back eventually.

How long does radiation extend life?
We were told that the median added life time following radiation therapy is 18 months. That means that some dogs live longer, and some don’t live as long. IT was explained to us that the distribution looks roughly like a bell curve, with 18 months being in the middle, and most outcomes falling close to the median. However, a small percentage dogs live much shorter than that and some live much longer.

How much does radiation cost?
Radiation therapy isn’t cheap, and the cost can be a deciding factor for many, especially those without pet insurance. While the actual costs of radiation therapy is around 7 to 8 thousand dollars (in Texas … your results may vary), when you add the required MRI and CT scan, plus multiple specialist visits, a more complete figure is closer to 11 or 12 thousand dollars.

The costs for SRT and conventional radiation are about the same. While newer machines cost more to use, with conventional radiation you have to pay for 20 hospitalizations and 20 rounds of anesthesia vs 5 or fewer with SRT.

How long does each radiation treatment last?
While delivering the radiation itself lasts only minutes, we still had to drop Jack off bright and early, before 8AM each day. And then after the treatment was done for the day, the doctor wanted to observe Jack for a couple more hours just to make sure he was OK and to wait for the anesthesia to wear off. Most days we were able to pick Jack up at around 3PM, but other days he stayed ’til 5PM.

Initial prep for radiation therapy takes a while, as doctors and technicians need to ensure the computer is calibrated to precisely target the brain tumor. They also have to make sure the molds used in keeping your dog’s head still (could be a mask or a “bite block”) are set up correctly so that they can reliably deliver radiation accurately to the correct location each day. As a result, we got Jack back after closing time on Day 1.

Other radiation considerations
Your dog needs to be healthy enough to get radiation treatment. Because radiation is hard on the body, and your dog will need to recover afterwards, treatment might not be right for all patients. Additionally, because multiple rounds of anesthesia can be risky, you will want to check with your general veterinarian to make sure everything else is OK first. They can also serve as impartial third party to guide you though the process.

In our case, we made sure to get a echocardiogram to make sure Jack’s heart would be strong enough for the procedure. If your dog has a heart murmur, we strongly recommend talking to a cardiologist or an internist before surgery. In general, if you have concerns about other health issues, do your homework and make sure to ask questions during your vet appointments.

Also, it’s better to get radiation sooner rather than later. Your dog will only get weaker as the brain tumor grows. Additionally, because there aren’t that many radiation oncologists, there’s usually a waiting list. If time is of the essence, don’t delay in scheduling an appointment for treating your dog.

Note: We’ve heard of some cases where a dog goes through something called “palliative radiotherapy” instead of the regular, more intense curative procedure because of other health concerns.

Jack’s initial radiation treatment results for cystic meningioma
As we mentioned before, Jack received 5 fractions of radiation during his SRT / TrueBeam treatment. Each day we got him back from the vet, we noticed some significant changes.

Day 1: 20% of dosage delivered — No big changes observed, but Jack was a little more fiesty than usual, which indicated that he was getting his energy back.

Day 2: 40% of dosage delivered — Appetite was coming back, and Jack was able to eat larger chunks of meat. Previously, his bite was weak and he could not chew or swallow some foods.

Day 3: 60% of dosage delivered — Jack loved to cuddle again, and stopped flinching when you reached to pet his head. This lead us to believe that he was in less pain. In fact, he started walking right up to us and demanding pets by nuzzling his head in our hands. His vision was much improved, and it felt like Jack was surprised to be able to see clearly again. He stared at us in the eyes very intensely, where before he would not make eye contact.

Day 4: 80% of dosage delivered — Jack’s sense of smell came back, and he started to sniff for the scent of other dogs outside, and he began to mark again. He also started lifting his leg up to pee for the first time in months. His appetite was ravenous after this treatment, where we would barely eat anything before. It felt like we were getting our dog back again.

Day 5: 100% of dosage delivered — Jack started making normal dog noises again. He began to whine to let you know what he wanted. He even walked up the stairs at the hotel a few times on his own. Previously, we had to carry him up every single time.