Osteosarcoma, or bone cancer, is a common cancer in dogs, especially in large and giant breeds. Approximately 85 percent of canine bone tumors are osteosarcomas. Over the course of more than 20 years, Flint Animal Cancer Center surgical oncologist Dr. Bernard Séguin has diagnosed and treated hundreds of patients with bone cancer. He has dedicated much of his research to advancing treatments to reduce complications and improve patient quality of life for this common canine cancer. Dr. Séguin recently reflected on his work with canine bone cancer.

How was osteosarcoma diagnosed when you completed your fellowship and started your career?

Osteosarcoma was often initially diagnosed based on “circumstantial evidence.” As FACC founding director Dr. Steve Withrow used to say “If it looks like a duck, walks like a duck, and quacks like a duck, what do you think it is? A duck!” What he meant is that if the lesion is in a large or giant breed dog, in a typical anatomic location, radiographically has the features of osteosarcoma, and the dog is not from an area with a fungal disease, then it is osteosarcoma until proven otherwise. So, we would move forward with the surgery to address the tumor in the bone based on this and then get confirmation of the diagnosis with histopathology once the tumor was removed. Interestingly, most dogs were evaluated with a bone scan back then. With all the dogs and data accumulated from doing these bone scans, they eventually figured out it was not necessary to do this screening in all the dogs.

What were the treatment options for canine bone cancer?

Treatment options were amputation or surgical limb spare for the tumor in the leg and chemotherapy to prolong survival. For owners who wanted a palliative approach, palliative radiation therapy was available. Surgical limb sparing was still considered cutting-edge at that time since it was offered in very few places.

What were patient outcomes?

For owners who chose to prolong survival with chemotherapy, the average survival was 10 to 12 months. Otherwise, survival was around five months. Sadly, these numbers have not changed in the last 20 years. Overall, dogs had a good to excellent quality of life while being treated and after having been diagnosed with osteosarcoma. But complications did arise, particularly in dogs with limb sparing and these could affect quality of life.

What advances have you seen in canine osteosarcoma diagnosis and treatment?

In terms of diagnosis, needle aspirates were not used to diagnose osteosarcoma and are now commonly used. This allows a relatively minimally invasive way to get a diagnosis before therapy. A needle aspirate is not rocket science but sometimes it is the simple solution that makes a big difference. Another advance is the adoption of PET-CT to determine where else in the body the cancer might be. This is definitely more complex but very powerful. As for treatment, stereotactic radiation therapy is an advance made in the last 10 years.

What challenges have you faced in treating bone cancer over your career?

Arguably, the biggest challenge has been to improve how long dogs live beyond their diagnosis. Being a surgeon, the challenge that I face is the complications seen with limb sparing surgery. As a result, I have worked on developing novel surgical techniques for limb sparing with the intent to decrease the risk of complications. Complications can be devastating for the dog and consequently the owners and can have such a negative impact on the quality of life.

What is considered cutting-edge treatment for canine bone cancer today?

I am particularly focused on using 3D technology to create personalized implants for the purpose of limb sparing. With this approach, an implant is created that fits the patient perfectly, as opposed to traditional implants that may not fit so well.

There are other treatment modalities that are currently being used or investigated to kill the tumor without having to remove it. In addition to stereotactic radiation therapy, other techniques include microwave ablation and histotripsy, but these are not used or offered at CSU.

While these modalities are very appealing because a big surgery is not required, what we have learned from the experience with stereotactic radiation therapy is that the bone is then at high risk of a fracture. The tumor might have been killed by the treatment, but the bone has been weakened by the destruction caused by the tumor and this is not changed with the treatment. So, we are looking at different ways to make the bone stronger to prevent a fracture.

One approach we have worked on is to develop a novel way to deliver bone cement into a bone after stereotactic radiation therapy to make it stronger. But that, in itself, is not a complete solution that addresses all the forces that can break a bone. We are also working on developing a new implant that would complement cementoplasty. Also, on the horizon but truly in the earliest stages of discovery in dogs, is a treatment that could help the body strengthen the bone without relying on a surgeon to place foreign materials in the bone.

Great Dane

Along the same idea of allowing the body to make its own bone, through a current pilot study, we are investigating bioreplaceable

implants for surgical limb sparing. The idea is that after the segment of bone that has the tumor is removed surgically, instead of using implants made of metal, we are using an implant made of a material that allows the body to grow new bone to fill in the defect. (Learn more about the first patient enrolled in this study.)

In addition to my work on the primary tumor site, I am collaborating with other teams to help develop therapies that are aimed at treating metastatic disease. In dogs with osteosarcoma, about 90 percent will experience metastasis. I am currently collaborating with a project looking at immunotherapy for osteosarcoma. A team of scientists at Northwestern University are looking into growing autologous tumor-infiltrating lymphocytes and natural killer cells from tumors with the goal of using these to treat metastatic disease.

How are we moving the needle?

Basic science is instrumental to develop new therapies. And new therapies are often developed when different disciplines come together. Therefore, collaboration is paramount to allow new ideas to flourish and be investigated to where they are available to patients. A good example is the amazing technology that had to be developed to create 3D printing. I’ve relied on collaborators in mechanical engineering to design and produce personalized 3D implants, and other partners to develop the bioreplaceable materials we are testing.

What are your hopes in the next 10 years for the diagnosis and treatment of canine bone cancer?

A cure! We cannot give up. We must find a cure but it is a very difficult nut to crack. On a more realistic level, my hope is to have treatments that will restore the normal health of the bone where the tumor grows and treatments that do a better job at prolonging survival than what we currently offer. From the diagnostic perspective, a reliable diagnostic test that is even less invasive such as a blood test. I think we are getting closer.