Introduction

In Hong Kong, about 180 children develop cancer each year. The incidence of childhood cancer is about 10 per 100,000 children. The common types of cancer in children are acute leukaemia, brain tumour, lymphoma, neuroblastoma and Wilms' tumour, whereas the common adult cancers, such as cancer of the stomach, breast and lung cancer are rarely found in children.

When cells in the human body develop cancerous change, they multiply at an abnormal rate. As these abnormal cells increase in number, they destroy the normal tissues and a cancer is formed. The cause of most cancers is unknown. Only a few childhood cancers are hereditary, congenital or associated with infection. For example, liver cancer is strongly related to previous hepatitis B infection.

Symptoms

The symptoms of childhood cancer vary with the cancer types. Acute leukaemia, for example, is usually associated with pallor, easy bruising and prolonged fever. Brain tumour usually causes headache, vomiting, blurred vision or loss of balance. Lymphoma or other solid tumours may produce lumps over the body, abdominal distension and bone pain.

Diagnostic Tests

The following are the examination procedures commonly required for the diagnosis and pre-treatment evaluation:

1. Blood test – Blood counts, liver function test, renal function test.
2. X-ray, ultrasound, computerised tomography (CT) scan or magnetic resonance imaging (MRI) – these methods of investigation will help to identify the site of the primary tumour and also the extent of the disease.
3. Tissue examination such as bone marrow examination, lymph node biopsy or excision of mass – to confirm the cancer type.
4. Lumbar puncture – some types of childhood cancer may spread to the brain and central nervous system. An examination of the cerebrospinal fluid by lumbar puncture (spinal tap) may help such diagnosis.

Based on these findings, the doctor will determine the appropriate treatment for the patient. During treatment, some tests or examination will be repeated in order to monitor the response to treatment.

Treatment

There are three main approaches to treatment for cancer:

1. Chemotherapy: The cytotoxic (anti-cancer) drugs can kill cancer cells and control their growth and proliferation. Medications may be administered by intravenous, intramuscular or subcutaneous injection, or taken orally. The duration of treatment depends on the type of cancer. It may last several months to two or three years.
2. Surgery: Most solid tumours, such as brain tumour or Wilms' tumour require surgery. Complete removal of the tumour will increase the chance of cure.
3. Radiotherapy: For some types of cancer, e.g. brain tumour and acute leukaemia, radiotherapy may be incorporated into the treatment regimen.

Most children do not require all three methods of treatment. The doctor will choose a combination of treatment considered best for the patient. The treatment may bring on some side effects, such as nausea and vomiting, hair loss, fever, anaemia and bleeding. However most of these complications are temporary, and will not cause permanent disability.

Prognosis

The cure rate depends on the type of cancer and the extent of the disease. With the advance of treatment, the cure rate of most cancers is improving. Children with acute lymphoblastic leukaemia now have about 70% chance of cure. However, other types such as neuroblastoma still show a low cure rate because they are usually at a late stage of development when diagnosed. Bone marrow transplantation provides another form of treatment, which may enable a better chance of cure for some previously considered ‘incurable’ cancers.