Osteosarcoma, also known as osteogenic sarcoma, is a type of bone cancer that’s commonly found in the limbs of canines.
It’s an extremely aggressive type of cancer that spreads quickly throughout a dog’s body. As one of the most common cancers in dogs, canines are said to be 15x more prone to the disease than humans are.
In this article, we’ll be discussing the causes, symptoms, diagnosis, staging and treatment options for osteosarcoma in dogs.
We’d like to thank the following veterinarians for their insightful contributions for this topic:
*Disclaimer: The information in this article is not meant to replace the advice and expertise of vets. You should consult a vet on your dog’s health condition for an accurate diagnosis.
Types of Osteosarcoma in Dogs
While this type of cancer can affect any bone, it’s mostly found in the front limbs near the shoulder, wrist and knee.
In some cases, the bone tumour can develop in the skull and spine, as well as in soft tissues such as muscles, tendons and mammary glands.
Osteosarcoma in dogs can be split into two main types: appendicular and axial.
Appendicular Osteosarcoma
Signs and symptoms• Instances of swelling at the affected bone
• Abnormal gait and lameness
• Increased lethargy
• Reluctance to participate in activities like walking and playing
Appendicular osteosarcoma refers to the development of cancerous tumours at the bones of the limbs and it accounts for about 75% of all osteosarcoma cases.
Starting from the core of a bone, the tumour grows outwards progressively and destroys the bone from within.
As time passes, the intensity of the pain increases with instances of swelling becoming more obvious as the tumour continues to grow.
Axial Osteosarcoma
Signs and symptoms• Instances of swelling at the affected bone
• Difficulty eating and loss of appetite
• Difficulty breathing
Axial osteosarcoma involves the growing of tumour cells in bones not related to the limbs. Some of the bones most commonly affected include the skull, ribs, vertebrae and jaws.
As axial tumours don’t progress as rapidly as appendicular tumours, they are difficult to detect as symptoms may be subtle.
In fact, it’s possible for an axial tumour to exist for 1-2 years before being discovered and diagnosed by medical professionals.
Causes of Osteosarcoma in Dogs
As with many other types of cancers, it’s difficult to pinpoint an exact cause of osteosarcoma in dogs.
Most cases of this cancer seem to be caused by a combination of several factors such as its genetic makeup and history of injuries. However, medical professionals are not 100% certain if the disease is also affected by environmental factors or nutritional factors.
Genetics
Dr. Leslie Brooks suggests that there could be a genetic component as large breeds of dogs with long limbs are found to have increased risk of suffering from the cancer.
Here are some breeds that are more susceptible to osteosarcoma:
• Golden Retriever
• German Shepherd
• Rottweiler
• Labrador
• Great Dane
History of Injuries
Dogs who’ve had a history of bone fractures or orthopedic implants also have an increased susceptibility to osteosarcoma. This is because these conditions stimulate the growth of cells for bone formation.
How to Diagnose Osteosarcoma in Dogs
A combination of tests may be required to accurately diagnose osteosarcoma in canines.
Radiography
Radiography, which mainly involves the production of medical imaging through X-rays, is one way to analyse the bone structure of a dog and to check for anomalies.
Limitations
However, there are certain non-osteosarcoma related ailments that resemble the appearance of cancerous bone tumors.
As such, further testing has to be done, and this may be done in the form of blood tests, urine analysis and tissue sampling.
Tissue Sampling
Fine Needle Aspiration
Fine needle aspiration (FNA) is a tissue sampling procedure that most doctors prefer over bone biopsy.
In FNA, a bore needle is used to extract a sample of cells from the tumorous bone.
Limitations
Although this method is sufficient to detect osteosarcoma, a radiographic diagnosis will usually be conducted to confirm the results.
Bone Biopsy
Bone biopsy is a form of tissue sampling whereby a small piece of bone is harvested for analysis under a microscope. Through a microscopic examination, it’ll be easier to determine whether cancer is present in the bone.
Limitations
However, one issue with this method is that it can be difficult to get an accurate and representative sample as the bone tumour is bounded by an area of swelling.
Furthermore, performing a bone biopsy can cause increased pain and lameness in the canine. In the worst of cases, the weak spot created from the hole may cause the bone itself to fracture.
Staging and Prognosis of Osteosarcoma in Dogs
Staging of osteosarcoma in dogs is categorised into 3 different stages and 2 substages. The stages are based on the TNMG system of tumour, node, metastasis and grade.
Stage 1: Presence of localised low-grade tumours (grade 1) without evidence of metastasisStage 2: Presence of localised high-grade tumours (grade 2) without evidence of metastasis
Stage 3: Presence of metastatic tumours
Substage A: Intramedullary lesions
Substage B: Local extramedullary spread
According to Dr. Joanna Woodnutt, most cases of osteosarcoma in dogs are diagnosed at Stage 2, Substage B.
Prognosis Factors
Dr. Woodnutt also provided insight as to some of the prognostic factors of dog osteosarcoma:
• Size of the tumour
The larger the tumour, the worse the prognosis.
• Location of the tumour
Dogs with osteosarcoma of the shoulder will have a worse prognosis.
• Age of the dog
Younger dogs (less than 7 years old) and older dogs (over 10) have better prognosis than those in the 7-10 year old group.
• Size of the dog
Smaller dogs (those weighing less than 40kg) have a much longer survival time on average. This may be because they can cope better with amputation and therefore have more treatment options.
Note!
On a whole, the prognosis for osteosarcoma in the long term is poor. Dr. Sarah Wooten shares that only 15% of dogs beat the odds and survive for a prolonged period of time after being diagnosed.
Treatment Options for Dog Osteosarcoma
Although osteosarcoma in dogs is treatable, there’s currently no known cure for the disease. As such, treatment usually focuses on either 1 of 2 main goals:
1. Easing the severity of the pain
2. Controlling the spread of the cancer as much as possible
(eliminates pain) | (reduces pain) | (reduces pain) | ||
(localised) | (systemic) |
Amputation
What is it and how is it done?
Amputation refers to the surgical removal of the affected limb. It’s the most common treatment option that dog owners opt for.
How effective is it?
Amputation is considered the best option for dogs struggling with intense pain, and it helps that dogs aren’t psychologically affected from the loss of a limb. Healthy dogs can also function perfectly well with just 3 legs.
Limitations
While amputating an affected limb can help a dog eliminate the source of pain, chemotherapy sessions are still advised to help control the spread of the disease and increase the likelihood of survival.
Limb-sparing Surgery (LSS)
What is it and how is it done?
Also known as limb salvage, limb-sparing surgery involves the removal of the cancerous tumour and the replacement of the tumourous bone.
How effective is it?
This procedure helps to greatly reduce the level of pain a dog has to manage, while still preserving the limb. However, the dog will suffer from a decreased range of motion.
Limitations
However, this surgery can only be performed if less than 50% of the limb is affected by the tumour. The feasibility of the procedure is also dependent on the location of the tumour.
Radiation
What is it and how is it done?
Radiation therapy is utilised to shrink the cancerous tumour and provide a form of pain relief for dogs with osteosarcoma. This is done by exposing the site of the tumour to high concentrations of radiation to kill the cancer cells.
How effective is it?
Radiation treatment is usually split into 3 doses over a month, with pain-relieving effects and improved limb functionality lasting for up to 4 months.
Limitations
The treatment has to be re-administered when the pain intensifies again.
Chemotherapy
What is it and how is it done?
While treatment options like amputation, limb-sparing surgery and radiation provide localised treatment at the location of the cancer cells, chemotherapy serves as a systemic treatment.
How effective is it?
Chemotherapy serves to control and contain the spread of cancer cells throughout the body, for as long as possible.
Limitations
Chemotherapy does not help with reducing the levels of pain a dog suffers from. It is generally provided after radiation treatments, or after the physical removal of the cancerous tumour through surgery.
Frequently Asked Questions
How long does my dog have to live with osteosarcoma?
Several factors affect the prognosis of your dog who has been diagnosed with osteosarcoma.
Some examples include
• the age of your dog,
• the extent of spread of cancer cells and
• the location of the tumour.
According to Dr. Amanda Jondle, the median survival time for dogs who don’t receive chemotherapy for osteosarcoma is expected to live between 6 to 12 months from the time of diagnosis, regardless of whether they had amputation.
How many cases of osteosarcoma occur in dogs per year?
According to the book A Dog in the Cancer Fight: Comparative Oncology in Osteosarcoma, it’s estimated that no fewer than 10,000 new diagnoses of osteosarcoma in dogs are made annually in the USA alone.
Can osteosarcoma in dogs be misdiagnosed?
It’s possible for osteosarcoma in dogs to be misdiagnosed. This is because the symptoms of bone cancer are both broad and subtle.
As such, this cancer can often be misdiagnosed as an injury or fracture, and other conditions such as arthritis.
When does osteosarcoma in dogs affect the lungs?
As lungs are blood-rich cells, cancerous cells are likely to metastasize there first. More often than not, the cancer has already spread to the lungs by the time visible symptoms such as inflammation are observed.
In fact, Dr. Wooten estimates that more than 85% of dogs diagnosed with osteosarcoma already have cancer spread to the lungs by the time they are diagnosed.
How painful is osteosarcoma in dogs?
Osteosarcoma in dogs is said to be incredibly painful, and the majority of vets would recommend amputation of the affected limb to alleviate your dogs suffering.
Are there any natural treatment methods for dogs with osteosarcoma?
Some natural treatments that owners have tried so far include incorporating supplements such as antioxidants and organic flaxseed oil into your dog’s diet.
However, these methods are not scientifically proven via research to be effective as of yet. Your best course of action would still be to seek expert advice from veterinarians.
Caring For Your Dog With Osteosarcoma
Finding out your dog has osteosarcoma can be distressing, but remember that you have to stay strong for your beloved canine.
When it comes to seeking treatment or simply caring for your dog with osteosarcoma, it’ll be best to seek professional advice from licensed veterinarians.
All pet owners are also encouraged to get the appropriate insurance policy for their pets to minimise the financial impacts from the potentially costly healthcare bills.
