Osteosarcoma is the medical term used to depict bone cancer. This is the most common form of bone cancer seen in dogs. It typically affects dogs belonging to large, giant dog breeds, predominately affecting their limbs. For this reason, osteosarcoma of the legs is often referred to as 'appendicular osteosarcoma'. The main bones affected are the long bones, therefore the ankle, hip and shoulder bones are the most commonly affected sites. However, osteosarcoma and other forms of bone cancer may also involve the spine, jaw, ribs and skull.
This disease mainly affects middle aged to elderly dogs, however at times it may strike at any age, sometimes even affecting younger dogs. Owners of breeds predisposed to osteosarcoma should therefore be aware of this possibility, and always keep it in a corner of their mind.
Symptoms Suggesting Bone Cancer in Dogs
Typically osteosarcoma develops deep within the bone causing the bone to gradually deteriorate from the inside out. As the bone is eroded and destroyed, it is replaced by a more fragile structure, known as 'tumorous bone'.
As the bones are weakened and replaced by 'tumorous bone', they become more and more prone to fractures that can take place with minor injury. Such fractures are medically known as 'pathological fractures' and unfortunately there is no way to allow such fractures to heal since there is really no healthy bone and therefore no viable supporting structure.
The main and first symptom seen in dogs affected by osteosarcoma is pain. Affected dogs may therefore develop lameness which at first may appear intermittent, going randomly on and off, but with time, the lameness becomes quite constant, becoming a chronic companion. In some cases, some local swelling can be seen and tenderness may be felt upon carefully palpating the bone.
To make things worse, osteosarcoma not only destroys healthy bones but it also tends to metastatize (spread) to distant organs. The most common cause of death in dogs affected by osteosarcoma indeed is metastasis to the lungs. Signs suggesting metastasis to the lungs are unexplained episodes of coughing and gagging.
How Bone Cancer is Diagnosed
It is unfortunate that often, treatment for bone cancer is delayed because owners and (vets too, sometimes) believe the dog is simply suffering from a temporary sprain. Therefore when they notice that after some rest and a few days on pain meds the dog gets back to being lame, more diagnostic testing is done.
At this point the first step to an accurate diagnosis is to have the limb x-rayed. Most cases of osteosarcoma are easily diagnosed this way, because veterinarians will notice right away areas where the bone has been eaten away. Yet, if the x-rays do not provide sufficient proof and other conditions need to be ruled out, veterinarians may request a bone biopsy.
Because pain is the main issue dogs affected with osteosarcoma must deal with, amputation of the limb is mostly recommended because it can greatly reduce pain therefore offering dogs some better quality of life.
However, bone cancer is a form of cancer with a high mortality rate regardless of treatment, and it is up to the vet to decide if the dog is a good candidate for amputation, while it is up to the owners to decide if they can financially afford such surgery. For those who can afford it, there are also several leg sparing surgeries available. According to Onlink.org, the average survival rate in dogs affected by osteosarcoma and treated with surgery and chemotherapy is approximately 1 year.