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A cancer of the young

Dr Anselm Lee Chi-Wai, a paediatric haematologist-oncologist at Parkway Cancer Centre, answers questions on osteosarcoma, a bone cancer.

What is osteosarcoma?

Osteosarcoma is the most common type of bone cancer. It is usually a disease of young people between 10 and 30 years of age. Osteosarcoma accounts for two per cent of all cancers in children and adolescents.

Other cancers that occur in the bone include Ewing sarcoma, Langerhans cell histiocytosis, and lymphoma.

What are the symptoms?

Pain is almost always the first symptom of osteosarcoma. But it is commonly ignored during the earliest phase.

Somehow, osteosarcoma tends to occur during the growth spurt when the child is approaching or going into puberty, and the discomfort from the disease is thought to be part of the growth.

Many a time, it is an unintended injury that brings the pain up for medical attention. Later, a swelling will appear. In some children, the affected bone may be broken (fractured) and the severe pain will send the child to the hospital.

Who are at risk?

The cause of osteosarcoma is still unknown. Boys develop osteosarcoma more often than girls. Children who have osteosarcoma tend to be taller than their peers. A small proportion of patients carry abnormal genetic changes that put them at risk for osteosarcoma.

Children with abnormal RB gene have a high tendency to develop an eye cancer called retinoblastoma. They are, at the same time, at risk for osteosarcoma.

Others with Li-Fraumeni syndrome (LFS) are at risk of getting sarcoma, leukaemia, and adrenal cancer. Their p53 gene is not working. Children who have been exposed to radiation therapy are also prone to develop osteosarcoma.

How is osteosarcoma diagnosed?

The thigh bone (femur) and the leg bones (tibia and fibula) are the most common bones affected by osteosarcoma.

A simple X-ray will give the doctor important clues for the diagnosis of the bone cancer.

A CT or MRI scan will show the characteristic findings of osteosarcoma. Getting some tissue from the tumour by a fine needle (biopsy) will provide a pathology and this is how an osteosarcoma diagnosis is confirmed.

Chest X-ray and bone scan, or PET scan alone will be used for staging to check if there is any spread of the cancer outside the primary disease location.

How is it treated?

Osteosarcoma is treated with chemotherapy and surgery. The standard treatment now is to give chemotherapy first for two to three months. When the tumour becomes smaller, it will then be removed by surgery completely. After the operation, there will be another five months of chemotherapy.

The chemotherapy regimen that produces the best treatment effect is with methotrexate, adriamycin (doxorubicin) and cisplatin (the MAP regimen).

The type of surgery recommended will depend on the extent of the tumour after chemotherapy is completed, with the primary aim of limb-salvage operation instead of amputation.

What are the chances of survival for osteosarcoma patients?

The chance of surviving osteosarcoma depends on the extent of the disease at diagnosis.

For children whose osteosarcoma is localised (no metastasis), the current long-term survival rates are between 70 and 75 per cent.

For children whose osteosarcoma has spread to some parts of the lung, the chance of long-term survival is about 40 per cent.

If the osteosarcoma has metastasised to places outside the lung, only 10 per cent of the patients can survive.

What are the complications of osteosarcoma and its treatment?

Children with osteosarcoma are at risk of losing one of their limbs affected by the cancer. Even after limb-salvage surgery, the child often needs some kind of grafts to replace the missing bone or sometimes prosthesis to substitute for joint functions.

Chemotherapy also carried short-term and long-term side effects. The immediate side effects include nausea, vomiting, mouth ulcers, sore throat, constipation, and diarrhoea. These side effects are reversible after treatment is completed.

Infections are the major concern during treatment, but careful monitoring and treatment with growth factors or antibiotics are often helpful. Hair loss can be the most unwanted side effect, but it will grow back after chemotherapy is over.

Methotrexate toxicities can sometimes affect the brain and the kidney. However, the chance that any of these will happen is very low.

Doxorubicin may have long-term side effects on the heart. And cisplatin may damage the hearing function and the kidney. Although severe hearing loss, heart failure, and kidney failure are uncommon, these functions must be closely monitored during and after treatment.