Radiation Side Effects

In a previous blog I mentioned how we use technology to minimize side effects to our pets when treating them with radiation.  However, there are many situations where we cannot or do not want to completely avoid normal tissues.  Almost all tumors have microscopic cells that extend into the surrounding normal tissues.  We often use the analogy of an octopus to describe a cancerous tumor.  The body of the octopus is the part of the tumor that we can see either with our eyes, or by some imaging (such as ultrasound, CT scan, MRI etc.).  If we just needed to treat this cancer would be easy to cure with surgery.  The cancer cells that extend into the normal tissue, like the arms of an octopus, often cannot be removed with surgery and these are often what we are treating with radiation or chemotherapy.  When we treat these cells we usually have to treat the normal tissues that they are invading into and this results in side effects in the normal tissues.

Radiation side effects in animals can be severe in some cases, but we are able to manage them, to get pets through treatment.  They usually start around the middle of a course of radiation, but they can get worse for up to a week after treatment is finished.  When the skin, the lining of the mouth, the eye or the colon is treated these side effects usually include redness and irritation of the area.  This looks a lot like a sunburn.  It starts as mild redness and itch, but usually gets worse until the area is very red and/or ulcerated.  When this happens pets usually need pain medications, anti-inflammatories and antibiotics to help keep the animal comfortable.  Fortunately we have many more pain options available for dogs and cats to help get them through this time.  The area is usually itchy so it is also very important that animals not be allowed to lick or chew at the area, so sometimes they need to wear a cone type collar to prevent this.

Fortunately for cats the short-term side effects are usually much less severe than in people or dogs.  Most cats who are treated with radiation usually just get dry, flaky skin or mild redness in the radiation area and they usually are not very painful.

Long-term side effects from radiation usually do not cause problems, things such as changes in hair coat color or thin skin.  Fortunately dangerous long-term side effects, such as bone destruction or radiation induced tumors, are typically very rare and can take many years to develop.

Although side effects from radiation can cause significant pain and discomfort, the radiation protocols that we use to treat animals are designed to try to minimize these effects so that we can get pets through treatment with as little discomfort as possible.

 

 

Dr. John Farrelly

New Technology for diagnosing and treating cancer in our pets.

We see technological advances around us every day.  Things that we couldn’t even imagine ten years ago are happening every day.  I am going to reveal my age here, but when I first started working with computers the text was green on a black background and graphics were cursor-sized boxes.  Today you might be looking at this blog on a smartphone while walking through the park.  Hopefully we use these changes in technology to make our lives better. 

 When it comes to caring for our pets the same is true and it is making a huge difference in the care that is available to our pets.  Today Computed Tomography or CT and MRI are available in many different centers.  PET scans (Positron Emission Tomography) These tools allow us to get an incredibly detailed look inside the body to identify diseases.  When it comes to cancer this is crucial to help diagnose tumors and to identify exactly where the tumor is in relation to the normal tissues.

However, this technology is not just useful for diagnosis.  New advances in technology are changing the ways that we have available to treat tumors.  There are approximately 70 centers in the world that have radiation therapy capabilities for treating animals.  Most of these facilities have linear accelerators for treating cancer, which allow us to focus radiation to the tumor, while avoiding the normal tissues.  Some of these facilities have a technology called intensity modulated radiation therapy (IMRT) or stereotactic radiation.  These techniques, used with advanced imaging techniques, allow us to truly pinpoint the radiation to the tumor, and minimize the dose of radiation to any normal tissues in the area.  By doing this we are able to effectively treat our pets with cancer, while making sure not to damage their normal tissues…helping us achieve our goal of effectively treating cancer, while keeping our pet’s quality of life as normal as possible.

 

I look forward to seeing what the next ten years brings to allow us to provide the best care possible for our pets.

Dr. John Farrelly

“Sammy-a simple story”

Sammy is a 9 year old Golden Retriever whose story is so simple yet so revealing that I needed to share it with you.

 

Sammy had no prior medical problems before being brought into the emergency service of one of our partner hospitals for a severely swollen left rear leg. On the initial examination, the leg was swollen from the tip of the toes all the way up to the hip. The swelling was among the most severe cases I had ever seen.  There was no history of trauma, no chance the dog was hit by a car, motorcycle or even bicycle.

 

Physical examination revealed no evidence of a fracture, insect bite, snake bite or anything else—just severe, severe swelling.

 

Unfortunately, as in many cases these days, finances were a big concern for the owner and she was considering having Sammy humanely euthanized. Our criticalist decided to try and convince her to see if –by chance—one fine needle aspirate of this swelling would give us the information we needed in order to save Sammy. Luckily the owner said “yes.” After checking the entire leg, a small area that was very slightly firmer than the rest of the leg was found. A fine needle aspirate was performed.

 

The aspirate revealed mast cells on cytology. The owner was devastated to learn that here beloved dog had cancer and again, she was considering euthanasia. But yet again, luck smiled on this very special dog. I convinced her to try one week of prednisone-before she made that final decision. By the following week, Sammy was a new dog. The swelling in his left rear leg had completely resolved—except for an area the size of a quarter right near his knee (stifle).

 

Because Sammy was now doing well, enjoying life and the massive swelling had changed to a small mass, the owner elected to have the mass removed. A “Trifecta”—the mass was found to be a low-grade mast cell tumor and our surgeon was able to get a complete excision. Sammy was cured.

 

This was not the most complex case, nor was it a case that required combination therapy or a new or novel therapy. What this case represents, is the value of a good physical exam, the value of honest heart-felt communications, and the value of hope (along with a little bit of luck).

 

Every time we see Sammy—we are so thrilled that his mom said yes.

 

 

Dr. Gerald Post - 2013

The Veterinary Cancer Center