The most common bone cancer is osteosarcoma.

Osteosarcoma a highly malignant bone tumor.

Bone cancer usually affects the limbs, but can also occur in other bones in the body.

Amputation or a limb sparing surgery can be performed to remove the tumor.

What is it?

• There are two types of bone cancer: primary and secondary.
  • Primary bone cancer is a type of cancer that originates in the bone itself.
  • Secondary bone cancer begins in another part of the body and metastasizes (moves) into the bone.
    
  • Secondary bone cancer may be difficult to treat if many tumors are present in other areas of the body.
    
  • Primary bone cancer in the limbs is treated by amputation of the limb if the cancer has not spread.
    Chemotherapy is usually needed after a limb amputation to provide the best outcome.

Pertinent Anatomy

• Bone tumors usually occur at the end of the radius (an arm bone) near the wrist, the end of the femur (upper leg bone) near the knee, and in the upper end of the humerus (upper arm bone) near the shoulder.

Clinical signs

• Breeds commonly affected
  
  • Large and giant breed dogs including Greyhounds, Rottweilers, Dobermans, Newfoundlands, and Saint Bernards
    
  • Small breed dogs and cats can be affected, but the risk is much lower than for large dogs
• Age
  
  • Older animals over seven years are mainly affected
• Sex
  
  • Males have a higher incidence of bone cancer than females
    
• Signs
  • Lameness or limping
    
  • Painful swelling that often occurs suddenly
    
  • Pathological fractures (fractures unrelated to an injury)
    
  • Weight loss and lethargy
    
  • Inappetite
    

Diagnosis

• Radiographs of the affected limb are needed to diagnose bone cancer. Radiographs of three views of the chest are also recommended to evaluate for spread of cancer to the lungs.
  
• A comprehensive blood profile including a CBC (complete blood count) and a chemistry panel is recommended to check internal organ function and to ensure that a safe anesthetic protocol can be selected for your pet.
  
• A urinalysis is sometimes used to further check internal organ function.
  
• A cardiac (heart) ultrasound is sometimes performed before chemotherapy. Certain kinds of chemotherapeutic drugs cannot be used in animals with heart muscle problems.
  
• Bone biopsies may be taken if the diagnosis of bone cancer is unclear. This procedure requires anesthesia and may require pre-anesthetic bloodwork to ensure the patient is cleared to undergo general anesthesia. In this procedure small bone pieces are obtained from the site suspected of bone cancer and sent to a diagnostic laboratory for interpretation.
• A bone scan should be strongly considered to look for spread of the bone cancer to other bones. This is not readily available, but we can make arrangements to have this scan done.
  
• If your animal has a history of hip or back problems x-rays may be taken of the pelvis in the case of a rear limb amputation. This ensures your dog can be mobile after the amputation surgery and that no other diseases are present that would contraindicate surgery.

Treatment

• Bone cancer is an extremely painful disease. Amputation of the affected limb is recommended to alleviate pain in the limb. Amputation requires that your animal undergo general anesthesia. The affected limb is removed surgically either at the shoulder (for a front limb) or at the hip (for a back limb). Most animals walk well after an amputation.
  
• In less aggressive types of bone cancer amputation alone can be enough to resolve the cancer.
  In more aggressive types of cancer chemotherapy is needed after the operation to extend the life of the animal.
  
• In some cases a limb-sparing surgery can be done if the tumor is at the wrist-end of the arm bone called the radius. In this procedure the part of the bone with the tumor is removed and replaced with a living bone graft from a donor animal (see photo above right). The graft takes about two to three months to heal. After the healing process takes place the animal is able to use the limb very well. Alternatively, a bone graft from a cadaver can be used.
• Another technique to salvage the limb is to place a metal spacer in place of a bone graft; the metal spacer is fastened to the bone with a very long, strong plate and screws (Kuntz endoprosthesis). See photo right.
  

Potential Complications

• Complications during surgery are rare but can occur. Death under anesthesia is a risk, but is lessened by pre-anesthetic testing to reveal under-lying diseases that may complicate surgery. The anesthetic risk is also lowered by sophisticated monitoring equipment such as an ECG (electrocardiogram) to monitor the heart’s electrical activity, blood pressure monitors, temperature probes, respiratory rate monitors, and pulse oxymetry to monitor oxygen saturation in the body. The use of gas-inhaled anesthetic agents, intravenous fluids and ventilators also lessen any risk of complications.
  
• Post-surgical infections are more common with limb sparing techniques that use the Kuntz endoprosthesis or the cadaver bone grafting technique (about 40%) but are rare following ampuation of a limb.
  
• Seromas may occur at the surgical site. A seroma is an accumulation of fluid in the tissues. The body will usually absorb the fluid, but the fluid is sometimes drained if needed.
  
• Cancer can sometimes recur at the surgery site or at other sites in the body. Signs that were present at the initial diagnosis of cancer should be monitored for after the surgery, including lameness, lethargy, inappetite, or weight loss.
  

Home Care

• After the amputation has been completed, intensive care in the hospital must be provided. Intravenous fluids may be administered. Most patients are able to return home after two days for an amputation and three days for a limb-sparing procedure.
  
• An epidural is administered before the surgery to control pain. In some cases an epidural catheter is placed for easy administration of epidurals for several days after surgery. Your pet may be sent home with an epidural catheter and injections for you to administer. A pain patch may also be placed on your pet to control pain. This is a clear plastic patch that gives pain medication through the skin for four days after the surgery. In addition, your animal may be administered oral pain medications for several days after the surgery.
  
• Your pet may have a bandage to cover the incision in place for several days after the surgery. The bandage should be kept clean and dry to prevent infection. The animal should not be allowed to chew or lick at the incision after the bandage is removed.
  
• Animals with amputations sometimes take a few days to learn how to walk on three legs. Usually after two to three days your pet will walk well.
  
• If chemotherapy is recommended for your animal it is generally started two weeks after the amputation surgery. Your animal will need to see an oncology specialist for this treatment. The chemotherapy is given every two to three weeks for ten to eighteen weeks.
  
• Your pet will have bloodwork done during chemotherapy to make sure he or she is not reacting to the medications.
  
• Side effects to chemotherapy are usually rare. Sometimes patchy hair loss can occur at the treatment site. Vomiting and weight loss can occur. Infections can arise as chemotherapy lowers the white blood cell count in the body. White blood cells help control infection in the body.
  
• Radiographs are taken periodically to ensure the cancer has not spread. Your animal should be observed for any abnormal signs (weight loss, lethargy, limping) during the post-operative time.
  

Prognosis

• Most animals do well after the amputation surgery. After the recovery period many owners report their animals are able to run and play normally again.
  
• In cases where the cancer has not spread to other body parts the limb amputation may be the only treatment required. These animals do extremely well post-amputation but must be monitored for recurrence of cancer.
  
• Animals receiving chemotherapy after the amputation usually have a survival time of about one year. Owners report their animal’s quality of life after the amputation considerably improves.