Bone cancer in dogs is considered one of the most common types of cancer, especially in large and giant breeds. Osteosarcoma is the most common type of bone cancer. In this article, you can find answers to the most frequently asked questions about osteosarcoma in dogs.
What Is Osteosarcoma in Dogs?
85% of bone cancers that occur in dogs are a type of osteosarcoma. Osteo means bone and Sarcoma means cancer. Osteosarcoma is an extremely aggressive type of tumor and causes painful destruction of the bone tissues in which it is formed. Osteosarcoma is usually seen in the bones that make up the limbs. However, it can also be seen in the bones of the skull, rib cage, spine and pelvis. Osteosarcoma can spread to the lungs. It is usually seen in middle-aged and old dogs. However, large breed dogs can also develop bone cancer at a young age. The tumor that occurs inside the bone grows outward and washes the bone from the inside. This causes a very painful process. If the tumor occurs in the feet, limping occurs in the limb. This limp can last for 1 to 3 months or it can be permanent. Over time, swelling in the tumorous bone becomes visible. The bone from which the tumor is formed is not as durable as normal bone and therefore can be broken easily. This type of broken bone is called a pathological fracture and is considered a finding that confirms the diagnosis of bone tumor.
What Are the Symptoms of Osteosarcoma?
The symptoms of bone cancer in dogs vary according to the location of the tumor, its stage or metastasis. Over time, a soft or hard swelling occurs in the bone where the tumor occurs. These tumors cause a lot of pain as they break down healthy bone from the inside. Limb tumors cause limping. As the disorder progresses, symptoms such as irritability, loss of appetite, weight loss, insomnia and inactivity also appear. In some dogs, fractures occur due to the weakening of the bone over time, and in this way the diagnosis of osteosarcoma can be made. Other symptoms vary according to the location of the tumor and other underlying tissues.
How Is Bone Cancer Diagnosed in Dogs?
In dogs with suspected bone cancer, a physical examination is first performed. Swelling occurs in the bone where the tumor occurs. In addition to a physical examination, blood tests, X-rays, and a bone scan may be done to see if it has spread to other areas. In some cases, fine needle aspiration or biopsy is performed. In dogs, osteosarcoma usually spreads to the lungs. PET – CT scan is performed to understand whether the spread has occurred. When the dog’s age, breed, location and appearance of the tumor indicate osteosarcoma, amputation can be performed directly without biopsy. Diagnosis and staging of cancer are very important for two reasons. First of all, it is necessary to determine the tumor type and extent of the cancer. Diagnostic tests also provide information about the dog’s general health. Accordingly, it becomes possible to identify concurrent medical, bone, joint, nerve or spine problems that may affect treatment recommendations.
How Is Osteosarcoma Treated in Dogs?
Treatment of osteosarcoma in dogs is generally divided into two. The first is to treat the cancer itself. The second is to control the pain caused by cancer. Some treatment methods meet both requirements. Successfully treating the pain allows the dog to live a comfortable and long life. Pain is controlled in two ways with pain amputation and palliative radiotherapy. Palliative radiotherapy is usually performed with periodic infusion of bisphosphonates. Amputation is one of the best choices when the cancer occurs in a single foot and has not spread to other locations. However, in cases where there is rheumatism and the cancer has spread to the other feet or lungs, radiotherapy is preferred instead of amputation.
Since the cause of the pain is the cancerous limb, amputation relieves the pain by 100%. The decision to amputate is a difficult one, but loss of one leg in humans greatly reduces mobility, whereas dogs are quadrupedal so there is no similar effect. After a foot is amputated, there is no change in running and playing. However, some problems can be seen only in cases of rheumatism. It is very difficult for people to get used to the appearance when a foot is removed, and this has a counterpart in the social environment. Dogs, on the other hand, are not conscious of their appearance and therefore do not feel any discomfort for their appearance after amputation. The important thing here is that the household is accustomed to the new situation.
Limping surgery is a treatment method adapted from humans to dogs. Tumorous bone is removed to protect the limb and avoid amputation. Instead, a bone graft is placed, or the remainder of the bone is regrown using a technique called osteogenesis. However, it is not possible to perform limp surgery in cases where more than 50% of the bone or peripheral muscle tissue is affected by the tumor. Limping surgery is not very successful when the tumor occurs in the hind legs. In addition, bone infection, implant failure, tumor recurrence and fractures may occur after limping surgery. Amputation is a pain management strategy, but when limping surgery is performed together with chemotherapy, pain is controlled. On the other hand, the creation of new bone structure is also a long healing period and it is necessary to be very careful after the surgery. However, when it is preferred for the appropriate patient, it is considered the most correct option.
In cases where amputation is not the right option, palliative radiotherapy treatment is preferred as an alternative. Radiation therapy can be applied as 2, 3 or 4 doses according to the treatment protocol. After the first 3 weeks, there is improvement in the functions of the limb. This situation lasts for 2 to 4 months. When the pain returns, radiation is required again. With the relief of pain, activity also increases. This may cause fractures in the tumorous bone. Palliative radiotherapy is not a method that benefits every patient. The probability of controlling the pain is around 75%.
The use of bisphosphonate drugs is one of the standard treatment methods for bone tumors in humans and is also useful for pain caused by osteosarcoma in dogs. Bisphosphonates act to inhibit bone resorption, which helps control pain and bone damage caused by a bone tumor. Bisphosphonate therapy is given as a serum application for approximately 2 hours every 3-4 weeks. Although the treatment has some side effects in humans, these side effects have not been observed in cats or dogs. Bisphosphonate is one of the methods that can be preferred especially in the absence of amputation.
There are different painkillers available to control pain caused by bone tumors in dogs. A single pain reliever does not help control the pain that occurs. For this reason, a drug cocktail is generally preferred. Among the most preferred drugs are non-steroidal anti-inflammatory drugs, narcotic painkillers and various types of painkillers. In the absence of amputation or radiotherapy, analgesic drugs are used. However, pain relievers have a very limited effect on the pain caused by bone cancer. Since the use of drugs does not completely relieve the pain, sensitivity to touch, limping or immobility may occur in the tumor foot over time.
Unfortunately, osteosarcoma is a tumor that spreads quite rapidly. By the time the tumor is discovered, it has usually already spread. This spread is usually towards the lungs. Another option for treating cancer is chemotherapy. Osteosarcoma is more aggressive and more common in younger dogs than older dogs. Chemotherapy has very dramatic side effects in humans. However, this treatment does not affect dogs in the same way. Dogs usually experience 1-2 days of lethargy and nausea. This situation can be eliminated with auxiliary drugs. Hair loss usually occurs in dogs that are constantly shedding, such as Poodles or Scottish Terriers. It is very rare in other species.