A few months ago, I flew to Seattle for a Veterinary Hospice conference. Osteosarcoma (bone tumors) was a big topic discussed in those lectures. I remember going to lectures in vet school, huddled around the power point screen armed with my highlighter. I was ready to learn everything, determined to be the best veterinarian that ever was. Our oncology professor was discussing different types of cancer. Each type of cancer required different radiation or chemotherapy with median survival days, and they all seemed to blur together until we landed on osteosarcoma.
I may have been looking at every disease with rose-colored glasses, as if there is some way to cure every patient if we just learned enough or tried a different chemo protocol. But this cancer seemed so much more sinister. I don’t remember learning anything about managing pain or any focus beyond recommending euthanasia as soon as possible. As a hospice veterinarian offering in-home pet euthanasia, and especially after going to hospice conference, I wear different glasses now. There is so much to learn about managing these patients’ pain. There are so many options beyond Tramadol and Rimadyl! As veterinarians, we fail you when we walk into a room and announce suddenly that your dog has CANCER and give you just some median survival numbers with or without treatment. I learned so much and I have come back armed with knowledge to share with you.
Here is a basic breakdown of the disease called osteosarcoma.
What is Osteosarcoma?
This is the most common bone tumor of dogs that usually affects the legs in large-breed dogs. Any bone may be affected, but 75% of the time the tumor affects a leg. The tumor develops deep in the bone and is very painful as it grows outward. The normal bone is being destroyed from the inside out. Dogs with these tumors usually have a history of intermittent lameness that progresses to constant limping. Many times, dogs are prescribed anti-inflammatory medications such as Rimadyl or Metacam. These NSAIDS (non-steroidal anti-inflammatory drugs) helps ease pain initially and the limping may resolve for a time, but as the tumor grows the pain worsens and the lameness becomes more severe. A swelling may also become visible as the normal bone is replaced by the tumor.
How Do We Diagnose Osteosarcoma?
The first step is to take x-rays (radiographs); a veterinarian will take x-rays of the affected leg. Often, there is a characteristic pattern of bone destruction (lysis) and new bone being formed at the same time. This type of tumor does not cross a joint but instead typically stays away from the elbow or heads toward the knee. Other parts of the body that this type of tumor may invade include the ribs, skull, jaw, or pelvis. These latter tumor locations are more common in small breed dogs. There are other types of tumors that may also affect bone including chondrosarcoma, hemangiosarcoma, and synovial cell sarcoma. Other tumors may also spread or metastasize to bones from other locations, and fungal or bacterial infection in the bone may have a similar appearance on x-rays.
Because so many different types of tumors may appear similar to osteosarcoma, your veterinarian may suggest a biopsy or fine needle aspirate to confirm the suspected diagnosis. A needle aspirate is often preferred since biopsy may increase the risk of fracturing unhealthy bone. The needle aspirate uses a large needle inserted into the tumor to remove some tumor cells. Certain stains are often used to confirm the diagnosis. It is also recommended that a full blood panel with urine analysis be sent to the lab to confirm the other organs are not compromised.
Chest x-rays may be ordered to determine there has not been pulmonary metastasis (visible tumor spread to the lungs) since this would change treatment recommendations. Always make certain your veterinarian has taken three views when checking for pulmonary metastasis. This means your dog or cat is positioned on his or her back, right side down and left side down. All three views are needed to be certain there are no tumors in the lungs. Unfortunately, 90% of dogs with osteosarcoma have microscopic spread to the lungs at the time of diagnosis, which means the tumor has spread to the lungs. Still, it is important to rule out visible spread to the lungs when considering palliative care or treatment options.
How Is OSA treated?
The biggest concern is pain management and stopping the spread of the tumor. Amputation is recommended to remove the source of pain. This is the best option to improve a patient’s quality of life. Many owners are reluctant to pursue amputation because they worry that the pet will not recover well. The reality is that dogs and cats do very well with only three legs and recover quickly following surgery.
A patient would not be considered a candidate for amputation if there has been visible tumor spread to the lungs (pulmonary metastasis) or if there is severe arthritis of the other weight-bearing legs. The median survival time for dogs who did receive chemotherapy for OSA is 3-5 months regardless of amputation (Source: VIN, Osteosarcoma, Wendy Brooks*). In other words, amputation does not seem to stop or slow down the spread of the tumor. Amputation is often a palliative treatment, meaning the surgery only provides pain relief.
Palliative Radiotherapy for Pain Control
If amputation is simply not an option, radiation may be directed to the tumor in 2-4 doses depending on the protocol. In most patients (75% of cases) there is improved mobility that lasts 2-4 months.
Another option is a class of drugs called bisphosphonates. These drugs are often used with palliative radiation. Bisphosphonates help suppress some of the tumor cells, osteoclasts, that are destroying bone; pain is therefore reduced. These drugs also reduce the risk of the affected bone breaking. A bone tumor replaces healthy bone tissue over time. A bone tumor is not as strong as healthy bone which means that with very little activity or force the bone may break, creating what we call a “pathological fracture.” Pathological fractures and pulmonary metastasis (tumor spread to the lungs) are the biggest risks or inevitable outcome of osteosarcoma. These drugs also appear to suppress tumor growth which means prolonging pulmonary metastasis.
The most common bisphosphonates are pamidronate and zoledronate. These medications are given as IV treatments. At this time, zoledronate seems to be a more practical pain treatment option due to fewer side effects and a faster treatment (15-minute infusion compared to several hours). Zoldronate is a viable option for pain control for patients that have not undergone amputation. This medication does require monitoring but may be given by a hospice veterinarian at home. Pain relief is often within one day with effects lasting up to 1 month.
Other pain medications to consider
There are many pain medications available for bone tumors, with the bisphosphonates showing the most promise. No single medication is a match for the pain, however, so it is important to consider a combination of medications.
These include NSAID (non-steroidal anti-inflammatory drugs) such as carprofen (commonly known as Rimadyl, Etodolac, Deracoxib, or Meloxicam). It is important to monitor liver and kidneys with these medications. These medications are considered the cornerstone of pain management and should always be part of a pain protocol if amputation is declined. Galliprant is a similar drug that is another option. Other pain relievers include Tylenol with codeine (for dogs only), Amantidine, Gabapentin, Tramadol, Amitryptaline, Minocycline, or Duloxetine.
What Does All This Mean?
The take-home message here is that amputation is best to remove the source of the pain, but there are other options to keep your pet more comfortable in hospice care. Talk to you veterinarian about options or contact Paw Into Grace today.
* Sources: VIN, osteosarcoma by Wendy Brooks and Dr. Shea Cox: Bone cancer pain lecture at International Association Animal Hospice and Palliative Care Symposium 2017