Brain Tumours - Tumours of the central nervous system (CNS-Tumours)
Author: Gesche Tallen, MD, PhD, Reviewer: Prof. Dr. med. Ursula Creutzig, English Translation: Dr. med. Gesche Tallen, Last modification: 2011/08/19
Brain tumours are the most common solid tumours occurring during childhood and adolescence and, following leukaemias, the second most frequent cancer in this age-group. They account for about 23% of all malignancies and can develop at any age. In Germany, approximately 410 children and adolescents below 15 years are newly diagnosed with a brain tumour each year. The incidence among boys is slightly higher than among girls (German Childhood Cancer Registry, annual report 2008).
A primary brain tumour or a tumour of the central nervous system (CNS), respectively, is a solid tumour in the brain or in the spinal cord arising from abnormal CNS cells which can display malignant behaviour such as uncontrolled proliferation or loss of their initial function.
The human CNS controls and regulates almost all our physical, mental, emotional and intellectual functions. It consists of multiple centres for various tasks consisting of many different types of cells. There are many different types of brain tumours in children and adolescents. The most common types, however, are medulloblastomas and astrocytomas. There are benign and malignant brain tumours. Yet, no matter whether the tumour is benign or malignant, the bony skull always limits the space that the growing tumour is occupying. This causes increased pressure in the head and harms vital regions of the brain, infiltrates them, and thus can have fatale consequences. Some brain tumours (medulloblastomas, ependymomas) can spread into the spinal cord. The occurrence of metastases outside the CNS is, however, very rare.
Like for other childhood malignancies, the factors responsible for the development of a brain tumour are not completely identified yet. We know so far, that leukaemia patients who received radiation of the brain as part of former treatment protocols, as well as patients with certain congenital cancer syndromes have an increased risk of developing a CNS-tumour. Neither environmental nor lifestyle factors have been proven to promote the development of CNS-tumours.
Histological type, localisation and size of the brain tumour determine the symptoms. Due to the increased pressure inside the skull, most brain tumours cause headache, vomiting, dizziness, and sometimes also impaired vision. In case of fast growing brain tumours, these symptoms often progress rapidly, whereas in patients with slowly growing tumours, these symptoms develop over a longer period of time. When a small child shows a disproportionately increasing head circumference, or when headaches recur or persist in a child or a teenager, they should see a doctor. The presence of a brain tumour should be ruled out, before other diagnoses, such as migraine, are made. Depending on its localisation in the CNS, a brain tumour can cause additional symptoms, such as gait disturbances, change in handwriting, seizures, various disorders of sensation, and/or paralyses.
To obtain (or rule out) the diagnosis of a brain tumour, various imaging procedures are used, in particular magnetic resonance imaging (MRI). When the brain tumour is located in a region that the paediatric neurosurgeon finds accessible for surgery (after having considered possible risks and complications), tumour tissue is usually obtained by biopsy or by (partial) tumour removal for histological work-up. The tumour type and degree of malignancy are classified according to the predominating cell type and its biological properties based on the World Health Organization's (WHO) Classification of Tumors of the Central Nervous System. The international classification of brain tumours distinguishes four different grades: benign tumours, for instance, are classified as WHO grade 1, malignant tumours as WHO grade 4.
Treatment depends on the type of tumour, its degree of infiltrative growth (spread to adjacent brain regions), its biology (WHO grade), the possible extent of tumour removal, and the patient’s age. The most common treatment forms are neurosurgery and/or chemotherapy and/or radiation therapy. Most patients with benign brain tumours (e. g. astrocytomas WHO grade 1 or 2) remain under observation (by a specialised paediatric oncology team) after the tumour has been resected. This means that regular physical control examinations/MRI will be carried out in order to detect a recurrent disease at an early stage and to apply appropriate treatment. In Germany, patients with malignant brain tumours (e. g. higher-grade astrocytomas or ependymomas (WHO grades II, III and IV) as well as medulloblastomas) receive an adjuvant chemotherapy and, depending on their age, radiation therapy of the CNS. Some tumours, e. g. tumours in the posterior fossa can cause a blockage of cerebrospinal fluid circulation, thereby generating hydrocephalus. This condition often requires a drainage (shunt-implantation or ventriculostomy) before the treatment of the tumour itself can begin.
Due to the vulnerability of the nervous system which is still developing during childhood and adolescence, the tumour as well as its treatment can cause physical, mental and psychological disorders, which require – even after the intensive treatment phase – professional long-term care. Thanks to standardised therapy concepts for the treatment of children and adolescents with brain tumours, the overall cure rates have increased during the last 10 years. At the same time, late effects resulting from therapy decreased due to continuously improved supportive care regimens. However, much more basic and clinical research is needed to define treatment concepts, by which the quality of life of long-term survivors can be further improved.
