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Osteosarcoma is cancer of the bone. It is seen more commonly in large or giant breed dogs and occasionally in cats. It is so common in Irish Wolfhounds that any lameness should be investigated as soon as possible. It can affect any bone in the body, but usually is seen in the long bones of either the front or rear limbs. It is a painful cancer because of its destruction of the bone in which it is growing. Hence, lameness is usually the first symptom noticed. The tumor itself, will not be obvious in the early stages and may not be seen on radiographs (X-rays). However, as the cancer progresses, it will be easily palpated (felt), and is usually diagnosed from the distinctive findings on radiographs. When it involves one of the bones of a leg, lameness occurs, and as it progresses, the lameness gets worse to the point the dog may not use the affected limb. In approximately 80% of cases, the cancer will spread (metastasize) to other parts of the body and often to the lungs. This spread, in most cases, has already occurred before the tumor is diagnosed.
If diagnosis is made early in the course of the disease, amputation of the affected limb is typically done, and many animals do extremely well after removal of the affected leg. In some cases, radiation plus a limb-sparing operation may be appropriate. Chemotherapy and/or immunotherapy may also be recommended to slow the progression of the cancer. However, in a number of cases, especially those involving geriatric or elderly animals, surgery, radiation and/or chemotherapy are not viable options.
In any case of osteosarcoma, pain management is important to keep the dog comfortable. NSAID’s are probably the most effective medications for pain relief with osteosarcoma, but because this cancer is so aggressive, even this class of medication can’t completely control the discomfort. Many veterinarians add opiates or opiate derivatives to the mix. However, in my experience, pain management using opiates or their derivatives, and other combinations of medications, can have detrimental effects on individual dogs to the point the animal is more uncomfortable from the medications than the cancer itself. Tramadol is an example, and is often part of the pain regimen veterinarians use. Please see my blog on the negative effects of this drug.
When this cancer involves an elderly dog, or a dog that is a poor candidate for any of the more aggressive treatment modalities mentioned above, I recommend using a bis-phosphate as an adjunct to the NSAID’s. Many oncologists recommend the injectable form of this class of medications, but the expense may make this approach unreachable. However, Fosamax (Alendronate), an oral medication used for treatment of osteoporosis in humans, has been shown to be effective in helping to control pain in osteosarcoma affected dogs. Its mechanism of action involves diminishing the breakdown of bone by osteoclasts, the main cell involved with osteosarcoma formation. If started early in the course of the disease, it can even slow down the progression of the cancer, especially if the involvement is in the lower front or hind limb. Please contact me for more information on how to use this medication if your dog has been diagnosed with osteosarcoma. It has to be given using a strict regimen of once a day treatment that also involves a NSAID that is given once a day (I recommend Deramaxx). It is best purchased via an application called GoodRx. All of this is important information that needs to be discussed before starting it.
Unfortunately, I am often called as an end of life consultant when the disease has progressed beyond the point of being helped with any of the above treatment plans. This is especially true when the cancer involves either the upper front leg (humerus or scapula) or the upper rear limb (femur or pelvis). Cancer in these areas tends to be more aggressive and amputation may not be an option, even in a young dog.
Most of the clients with elderly dogs that have been stricken with bone cancer, will not consider amputation or radiation or chemotherapy. Consequently, pain mitigation is the only possible approach for prolonging their dog’s life. That is why it’s important to be aware of the “good” pain relievers versus the “bad” ones.
Generally, if the pain from the cancer is minimized, many of these dogs, including the older ones, can continue to function well with three legs (they will not use the affected leg) even those with metastasis to the lungs. As the cancer progresses, however, the dog will become less and less able to move. This may also be compounded in the geriatric dog that also has neurologic weakness in the hind limbs. (see Geriatric Neuropathy under News). The earlier the diagnosis is made and the sooner adequate pain relief is prescribed, the better the dog will do. If amputation is performed, most dogs will be pain free after the initial recovery from surgery. The same may be true of the cases treated with radiation and limb sparing, and/or immunotherapy or chemotherapy. It’s extremely important to understand all of the possible treatment modalities and their side effects.
Following are several links to websites that will give you more information.
https://www.iwfoundation.org/articles/fosamax-revisited-12-06-2012
https://pubmed.ncbi.nlm.nih.gov/10958534/
BONE CANCER IN DOGS
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