Canine bone cancers: Understanding the different types

Having your vet tell you that your dog’s diagnosis is cancer of any form will of course be very shocking and distressing, but when it comes to bone cancers this can be even more so, as many dog owners don’t really understand how bone cancer occurs and what problems it causes. Additionally, while “bone cancer” is widely used as a catch-all heading to explain the basics of what is amiss, there are actually several different types of canine bone cancers, each of which has a different action, set of symptoms, and prognosis for the dog in question.

Your vet will be able to talk you through the full details of your dog’s diagnosis, what this means for them and how treatment or management might be attempted; but in this article, we will provide a basic introduction to the various different types of bone cancers that can affect dogs, their action, and likely prognosis. Read on to learn more.

Primary bone cancer

The term “primary bone cancer” is used to describe cancers that originate within the bones themselves, rather than those that begin in another area of the body and then spread to affect the bones themselves.

There are three different types of core primary bone cancers, which are fibrosarcoma, osteosarcoma and chondrosarcoma respectively, and we will look at each of these in a little more detail further on.

Metastatic bone cancer

Metastatic bone cancer is also sometimes referred to as secondary bone cancer, and this is the type of cancer that originates elsewhere in the body and then spreads to affect other areas, such as the bones. This type of bone cancer is usually quite acute and aggressive, because once a cancer has begun to spread systemically throughout the body, it becomes exponentially much harder to treat.

In order to be able to attempt treatment of metastatic bone cancer, the original cancer itself must first be removed/treated or brought under control, and once this has been achieved, treatment of the bone cancer itself can be attempted.

This type of cancer is often complicated and has highly variable outcomes, depending on the severity of both the primary source of the illness and the bone cancer itself. If the original tumour or source of the cancer cannot be treated or placed into remission, any attempt to treat the bone cancer on its own will produce only limited or temporary results, and is unlikely to prove successful in and of itself.

Fibrosarcoma

Fibrosarcoma are slow to grow and don’t tend to spread widely nor become systemic, although there are exceptions in the rarer cases that can occur with particularly high-grade tumours. Fibrosarcoma begins in the bone’s fibrous connective tissue adjoining the bones-hence the name-and usually present as lameness or loss of strength, balance and soundness in one or more limbs, which may appear to be very mild and/or come and go.

Treatment is often possible, and chemotherapy, radiotherapy or surgery may be indicated. However, due to the location within the bone and connective tissues where fibrosarcoma usually presents, often the best choice is amputation of the limb in question in order to ensure that all of the cancer is removed and will not spread or return.

Chondrosarcoma

Chondrosarcoma occurs at the ends of the leg bones in the cartilages that connect the joints, and once more, lead to symptoms such as lameness in the affected limb that may come and go, and general unsoundness and changes in gait. Like fibrosarcoma, chondrosarcoma is not a particularly aggressive nor fast form of cancer, and rarely spreads systemically outside of the affected area.

Again, various modes of tackling the cancer such as chemotherapy and radiotherapy may be considered, but amputation of the affected limb is once more usually considered to be the best long-term resolution.

Osteosarcoma

Finally, osteosarcoma is a very aggressive type of bone cancer that is highly malignant, fast-spreading, and over time will almost invariably spread to the major organs such as the heart or lungs, which is often the ultimate cause of death in affected dogs.

Osteosarcoma develops within a specific type of bone cells that produce minerals that help to create and strengthen the bones, and unfortunately, by the time osteosarcoma begins to show symptoms, it is often very acute and challenging to treat. The symptoms of osteosarcoma are shared with both fibrosarcoma and chondrosarcoma-lameness that may be mild or acute, and that may seem to come and go.

In order to have a potential chance of treating osteosarcoma in your dog, an aggressive approach is required. Removal of the leg containing the cancer is usually hard to avoid, and chemotherapy is usually indicated after amputation too. Dogs that have had both an amputation and successful chemotherapy may survive and be able to maintain a good quality of life despite their missing limb for years rather than months, whilst amputation alone rarely extends the dog’s life for more than a few months.

Unfortunately, osteosarcoma is also the most common form of canine bone cancer-however, being aware of this can help to ensure the vigilance required to seek diagnosis and treatment promptly as soon as the dog becomes symptomatic, thereby giving them the best odds of survival.