Dogs are often afflicted with many of the same diseases as found in the human species. Whether they occur in the soft tissues of the muscles and organs, or in the hard skeletal frame of the bones, dogs many times develop severe illnesses that have to get serious attention at the veterinary hospital. Osteosarcoma in dogs or cancer of the bones is a disease that presents one of the more serious challenges to dog owners. Dogs do develop several types of bone cancers, but osteosarcoma is the commonest occurring in 85% of bone tumors.
Bone tumors affect mainly the appendicular (limbs) of larger dogs. However, the cancer also grows in the axial areas such as the sinuses, the skull, ribs, and vertebrae, but these are found mostly in the smaller canines. The tumor grows from inside the bone to the outer part destroying the tissues of the bone and making it extremely brittle. A dog with osteosarcoma will easily break a bone while jumping or running and this can be an extremely painful condition.
Very often osteosarcoma is not diagnosed until the late stage and 90% of the time it has metastasized or spread to other parts of the body mainly the lungs and surrounding bones.
What are the chances of your dog getting osteosarcoma?
Size and age – Osteosarcoma is found mainly in larger and giant breeds of dogs and Golden Retrievers, Great Dane, Irish Setter, Doberman Pinscher, Rottweilers, Greyhounds and Flat-Coated Retrievers are especially prone to appendicular bone cancer because of their size and weight. Smaller dogs are most likely to get the cancer in their ribs. It has been found also that older dogs from 7 years on in the larger breeds have a higher chance of developing the disease. Smaller adult dogs are more disposed at between 4 1/2 and 5 1/2 years.
Previous trauma – A known cause has not been found for osteosarcoma in dogs. However, several possible factors seem to have links to a dog developing the disease. Dogs that have had trauma to a bone previously tend to develop the disease. Where a previous fracture to the bone is healed, bone growth tends to occur. Dr. Kim Cronin, Oncologist at the University of Pennsylvania indicated that the disease usually anchors itself where bone remolding has occurred.
The doctor explains that where there are occurrences of cell damage, and the cells seek to reconstruct their DNA when healing, errors in coding occur and cell growth usually takes place in the area resulting in tumors (Osteosarcoma (bone cancer), n.d.).
Implants – Implants in bones sustained through several activities are also suspected for the development of osteosarcoma. Metal implants to hold broken bones and joints together, bullets lodged in the skeleton, and bone transplants have been presented as factors that influence cell growth.
Additionally, it is well known that dogs that have been injected with plutonium during experiments develop osteosarcoma, in addition to those that had sex hormone applied or have had their gonads removed. A 2002 study of both male and female Rottweilers found that a quarter of the animals that had elective gonadectomy developed spontaneous osteosarcoma later (Cooley et al, 2015).
Genetics – Genetics has also been found to play some part in the development of osteosarcoma. In clinical experiments conducted, osteosarcomas have been found to contain the p53 tumor suppressor cells.
What are the signs of osteosarcoma?
The most pronounced sign exhibited by a dog with osteosarcoma is lameness. You may observe that your dog suddenly is limping and he is having difficulty placing his foot on the ground. Lameness may come as a result of a fracture that occurs in the bone and it therefore becomes very painful. A dog with osteosarcoma will also develop a painful mass or swelling in the area of the bone which is affected. The swelling occurs because the tumor extends from the inner part of the bone into the surrounding tissues.
Dogs with axial skeletal osteosarcoma will display symptoms depending on the primary site of the cancer. Cancer in the bones of the lower jaw regions will see your dog having difficulty swallowing and opening his mouth. In the orbital areas (surrounding the eyes) the eyes may bulge from their sockets. The dog’s face may look somewhat deformed, and there are instances of excessive nasal discharge.
The dog may also become very sensitive to heat, light or other stimuli. Those cancers that develop in the bones of the spine and the skull will cause the dog to experience neurological problems such as seizure, while pelvic cancers will cause diarrhea.
The symptoms described here can be very painful and your dog may constantly whimper, and lose its appetite resulting in weight loss. Your dog may also find it difficult sleeping, becoming lethargic, and refuses to exercise. Because of the pain he may understandably become irritable and aggressive.
How is osteosarcoma in dogs diagnosed?
Several methods are used to get a definitive diagnosis on osteosarcoma. According to the Ryan Veterinary Hospital at the University of Pennsylvania, the diagnosis is important to determine the type of cancer, while providing information on the general health of the dog.
The procedure may also identify any co-existing medical problem that could be affecting the dog, and all of these will determine the type of treatment that he will get.
- Examine the dog yourself – Usually it is the dog’s owner who would have started the process of diagnosis because you have observed some signs that you are not comfortable with. Give the dog a light physical examination to determine painful regions, raised or swollen areas, and other signals such as sensitivity. This information you will take to the vet who will start a physical examination of the animal.
- Physical examination – The vet will conduct a physical examination taking into consideration what you have observed about your dog. The physical will identify any mass that may be present, observe any neurological symptoms, and inform other methods of examination to better determine the problem. Additionally, the doctor will examine other areas for tenderness and pain that may suggest that a tumor may have spread to other sites.
- Radiography (X-Ray) – The oncologist will ask that a radiograph or x-ray of the affected and surrounding areas be done. The radiograph will show in a sunburst pattern where any bone is protruding or where there is a deterioration of bone mass. Usually a radiograph of the lungs is also called for.
- Biopsy – Where the radiograph is not clear enough to make a definite diagnosis, the oncologist will also do a biopsy. The biopsy involves a small incision to remove a piece of the affected area to test for cancer. The doctor could do either an incisional biopsy, removing just enough for diagnosis, or an excisional biopsy where the entire tumor is removed and tested.
A biopsy is mandatory because tumor cells are not distinct enough in the initial stages and therefore may not be pronounced on the radiograph. Also, you want to rule out other problems that can resemble osteosarcoma such as fungal bone infection. A biopsy however is a delicate procedure as the process can result in the spread of cancer cells. Because the primary area is bone in itself, it is difficult to be able to gather enough bony material for testing. Also, care has to be given as there is a risk of bone fracture.
- Advanced imaging – The doctor may also order advanced imaging such as Magnetic Resonance Imaging for short MRI, or a CT scan which are more invasive in detecting cancer and if there is spread to other regions.
What are the options for treatment?
Osteosarcoma is a very aggressive disease which demands very aggressive means to combat the problem. The treatment of canine osteosarcoma is of two purposes: to reduce the pain caused, and to provide a better quality of life for the dog. Several treatment options exist; but your dog’s general health and the extent of the spread of the cancer will determine which method is used to make him better. Most likely the intent is to apply curative treatment to a cancer that is contained in its primary location. This could mean administering one or a combination of treatments for a cure.
Amputation – One of the first options in appendicular osteosarcoma is to amputate the affected limb. This sounds like a radical way of dealing with the cancer but the operation serves the purposes of removing the tumor and eliminating the source of pain. This will significantly improve the quality of life for the dog and unlike humans, dogs usually adjust to their new condition quickly and are back to their old ways, engaging in running and jumping.
Dogs that are overweight will find activities stressful however on three legs, and it is therefore a good idea to place him on a diet before surgery or in the process.
Limb-sparing surgery – You can choose the option not to remove the limb of your dog in the case of osteosarcoma and instead remove just the area of the tumor. Dogs with small tumors are the best candidates however. This option is also recommended where the dog has a pre-existing orthopedic disease or neurological condition and full removal of the limb would cause further complications.
The operation is also generally a suitable choice when the tumor is confined and has not been spread to other locations. Additionally, if there is a fracture and where the cancer does not involve a great deal of the soft tissue, then limb-sparing surgery is considered. The best candidates for this procedure are dogs with tumors in their front leg at the “wrist”. In this procedure only the tumor is removed and grafting of the bone is done to repair and grow new one in the affected area.
Chemotherapy – Generally osteosarcoma has already metastasized to other parts especially the lungs by the time the disease is discovered and diagnosed. The greater the spread the less of a survival outlook there is for the dog. Chemotherapy is used to help to stop the spread and by administering drugs like Cisplatin, Carboplatin and Doxorubicin to the animal can prolong life beyond amputation or limb-sparing surgery.
With surgery alone, the dog has a life expectancy of 4 – 6 months. However when chemotherapy is applied, especially in conjunction with other therapies, survival is extended to one year.
Radiation – When amputation is not considered as an option for treatment, radiation is given as a means of palliative care. Radiation therapy is geared towards eliminating pain, inflammation and swelling in the dog so that his quality of life can be improved. The dog is given 3 doses of the treatment weeks apart for about five weeks. Dogs generally benefit from this type of treatment quickly especially if combined with pain medication. Relief can last for 2 – 4 months and the doctor may recommend that the next dosage be given in one month to extend the period of pain relief.
Radiation therapy has its risks, however. For one, when the pain is relieved after treatment, the dog feels a whole lot better and tends to resume its normal activities of movement. This can result in fractures and aggravation of the problem. In addition, treatment directed at a particular area of the body creates the tendency to develop redness and dryness of the skin called radiation dermatitis. This actually looks like sunburn. However a topical cream from the doctor can soothe the area.
The growth of osteosarcoma in axial regions is not as rapid as in the appendicular bones and the problem is therefore more difficult to treat. The same methods of treatment are applied, however.
How do you care for a sick dog?
Maintain normal activities – Many dog owners will never accept the idea of their dog being amputated, since they cannot imagine them surviving on three legs only. However, as aptly indicated at caninecancer.com dogs do not have any social hang-ups about walking around on three legs. It is us humans who are self-conscious about our appearances after losing a limb to surgery and rightly so for the social implications. Dogs will be back to their normal self as soon as an amputation is carried out, once they are in otherwise general good health.
As the dog owner, you may be the one who needs to get used to seeing your dog in an unusual condition. Therefore, the dog will expect that you treat it in the same way as you normally did.
Handling complications – It is said that 10% of dogs that have had limb-sparing surgery have had some form of complications. Implant failure, infection, and recurrence of the tumor are possible and therefore you will need to monitor your dog and follow-up with the doctor for treatment. There is no known specific reason for infection, but it is thought that poor coverage of the soft tissue, use of orthopedic implants and applying doses of chemotherapy drugs can all complicate the dogs system and make him prone to infection.
Help your friend – Although your dog may want to run and skip along, you may need to put a bit of control on him so that he doesn’t fracture the leg in the case of limb-sparing surgery. Amputees also may need to go easy especially if they are overweight since this could place excessive pressure on the other limbs. Another way that you can help your dog is to keep floors and walkways free from clutter so he does not go bouncing into and breaking things.
You could also purchase material that gives some traction to help him when he is getting up. Sandy, owner of Bo was hardly prepared for the changes in her dog after surgery. Ice and laminate floors were suddenly dangerous places to be. Bo was not able to climb stairs, jump into the car, and walk up ramps or even a slight hill. In these instances he had to be carried in a sling. She had to be extremely careful when handling the dog on a leash for with a slight correction the dog could topple over.
These are some things that you may not hear from the vet, but will discover on your own.
Palliative care – Osteosarcomas can be extremely difficult to treat especially when originating in the axial regions. The disease can also cause excruciating pain and treatment can take a toll on the animal. In many cases you can only help by providing palliative care, giving support and comfort to the rest of life.
The energy will wane, the immune system destroyed and healing can be slow. You can make life bearable by giving food that is easier to chew and swallow, and that has less carbohydrate and more protein. Palliative care should include medicine to relieve pain and make quality of life as comfortable as possible. Just being there for your dog will also help.
Osteosarcoma in dogs can change the life of a dog and its owner in dramatic ways. It is important therefore, that everyone who loves and owns dogs is aware of the behavior of the disease and knows how to handle it. Pain and other symptoms are part of the process. But fortunately you can lean on the knowledge and expertise of the professionals to maintain a good quality of life for dogs with the disease. As dog owners, you should also give some consideration in how to handle the dog in its condition.