The bone cancer that often develops in the tibia (shinbone) near the knee, humerus (upper arm bone) near the shoulder, and the femur (thighbone) near the knee is called osteosarcoma. Osteosarcoma is one of the most prevalent types of malignant bone cancer. It accounts for at least 3 per cent of the cancers that develop in children.
While other types of cancer can end up spreading to the bone, osteosarcoma is one of the few that begins in the bones and can spread (or metastasise) to other parts of the body. Most cases of osteosarcoma often occur during growth spurts in adolescence. This type of cancer is also more common among boys than in girls.
Osteosarcoma symptoms can vary depending on its location. However, some of the most prevalent symptoms of the condition include:
- Bone pain (when lifting objects, while in motion, and even at rest)
- Bone fractures
- Limitation of joint motion
The severity of pain brought about by the condition can vary from one patient to another. While some will notice only dull pain, others may experience the kind that keeps them up at night. In addition, people with osteosarcoma may notice that the muscles in the affected area may appear smaller (atrophy). Some symptoms of the condition can mimic growing pains (i.e. leg pain secondary to normal bone growth). However, if the pain persists past their initial growth spurts or if the pain is causing severe pain or discomfort, seeing a doctor is recommended.
A variety of tests may be used to accurately diagnose the condition. When conducting a physical examination, the doctor will look for signs of redness or swelling. Medical history, previous illnesses, and past medical treatments of the patient will also be looked into. A simple blood test may also be required to check for tumour markers (alkaline phosphatase). Tumour markers are chemical readings in the blood that will indicate cancer presence.
Other tests that are used to help diagnose osteosarcoma can include:
- X-ray – can produce images of the hard (calcified or ossified) tissues inside the body, including the bones
- MRI scan – makes use of powerful magnets and radiofrequency waves to produce images of the internal organs
- CT scan – a 3D X-ray used to examine the soft organs and bones
- PET scan – a full body scan using a special tumour marker (usually used to detect cancer)
- Bone scan – an imaging test that can show abnormalities in the bone that other imaging tools may miss. Bone scans are also used to check if cancer has spread to other bones.
- Biopsy – removal of a tissue sample from the bone for testing
Treatment of osteosarcoma can include chemotherapy (drugs used to kill cancer cells), followed by surgery to remove the tumour or cancerous cells. In most cases, surgery can effectively remove the bone cancer while chemotherapy can help ensure the remaining microscopic cancer cells in the body are eliminated.
Surgical treatment for osteosarcoma can be amputation or limb-salvage surgery. Nowadays, osteosarcoma in the leg or arm is often treated with limb-salvage surgery instead of amputation. In limb-salvage surgery, the bone and the muscle affected are removed. A gap will be left in the bone and is filled by a bone graft (often from a bone bank) or a special metallic tumour prosthesis. These may be matched to the size of the bone defect. However, since there is a higher risk of fracture and infection with bank bone replacement, metal prostheses are often used when reconstructing the bone after the tumour removal. If cancer has spread to the blood vessels and the nerves surrounding the original tumour, amputation is often the likely option.
However, amputation can come with short and long-term side effects. For instance, it will take at least 3 to 6 months before the patient will be able to learn to use a prosthetic (artificial) arm or leg proficiently. And that is just the start of a long social and psychological rehabilitation. Oftentimes, with limb-salvage surgery, the patient can already bend the knee (or the affected body part) almost immediately.
For children with tumours around the knee, a continuous passive motion (CPM) machine may be used to help improve motion. Rehabilitation and physical therapy for 6 to 12 months after the surgery can help the patient walk (with crutches or walker, initially) and then without any assistive devices eventually.
Post-surgery complications can include slow healing of the surgical wound and infection. In some cases, the bank bone or the metal prosthetic device may require replacing as the body grows, or when implants lose fixation after many years of use. In addition, chemotherapy may also result in unpleasant side effects. Some of the likely side effects can include:
- Hair loss
- Tingling in the arms and legs
- Fluid retention
Fortunately, the survival rate for osteosarcoma that has not spread to other parts of the body is at 60 to 80 per cent. Also, osteosarcoma that develops in the leg or arm often has a better prognosis compared to those that develop in the shoulder blades, spine, ribs, or the pelvic bone.