Tumours in the central nervous system
OUTLINE
There is a difference between the central nervous system (CNS), which is composed of the brain, the cerebellum and the spinal cord and the peripheral nervous system, which is made up of all the nerves which run through the body and the structures which surround the nervous system. Tumours in the nervous system are rare: their incidence is not more than forty to sixty per hundred thousand. The majority of these, especially those of the central nervous system, are malignant. In Belgium, this type of tumour represents less than 2 % of all cancers. In a child, tumours of the CNS are the main cause of death from cancer. By and large, the causes which are responsible for the development of these tumours remain unknown. Ionising radiation comes first in the risk factors for cancerous tumours. The impact of radio waves emitted by mobile telephones on our brain is debated amongst the scientific community.
SYMPTOMS
There are four signs which might indicate a tumour in the brain: intracranial hypertension (headaches, nausea, vomiting and changes visible on examining the back of the eye), manifestations of epilepsy, motor deficits (weakness in a part of the body) and cognitive disturbances (disturbances in memory and confusion). There is however no need to panic: the vast majority of headaches for example have nothing to do with brain tumours. Tingling or loss of strength in one or several limbs, or in a segment of the body are alarm signals of a tumour of the peripheral nervous system, but these signs may also occur in many other complaints.
DIAGNOSIS
Apart from classical examinations using medical imaging and analysis of sample tissues under the microscope, the tool of choice for diagnosing SNC tumours is magnetic resonance imaging. This non invasive technique which has no secondary effects supplies high precision images in 2D and sometimes even in 3D. There are other additional imaging techniques, such as the PET Scan, and they help to draw up improved surgical intervention by targeted diagnosis and/or therapy.
TREATMENT
Patients suffering from cancer of the CNS are looked after by a multidisciplinary team where neurosurgeons, neuroradiologists, neuroendocrinologists, neurologists, medical oncologists, anatomical pathologists and radiotherapists approach each patient case together so as to ascertain a treatment which is best adapted to each situation.
The initial treatment for most initial brain tumours is surgery. More than 200 patients are operated on each year at Saint-Luc University Clinics, for malignant and benign tumours of the nervous system. In this institution a complex, ultra-modern surgery has been developed which is set to be a global leader for at least a few years yet. A very high-field MRI room is combined with a neurosurgery room. This allows the quality of the intervention to be monitored, even though it is not complete.
Surgical techniques have evolved very much in the last few years. Neuro-navigation, which has been used for 11 years, enables surgery to be carried out with computer assistance. The device shows the information in the microscope eyepieces, which the surgeon uses to operate. It is a little bit like GPS for a surgeon. Thus a lesion can be located with great precision and, using the computer screen, the neurosurgeon knows the exact position of the instruments in the patient’s brain and can therefore determine, with a great deal of precision, a path to the chosen target area. This technique is essentially used for pathologies which require millimetric precision, such as when operating on cerebral tumours. The benefits of this surgical method are key for the patient since comfort is markedly improved. Moreover, thanks to the millimetric precision of these interventions, the operating area can be better targeted for very small openings. The risks are thus limited; the patient wakes up faster and the length of stay in hospital is shorter.
The very high field MRI room has equipment which is the only one of its kind in the world and is connected to a neurosurgery room. Neuro-navigation has become a routine practice.
Often the tumour cannot be completely removed due to its infiltration, and there is a risk of considerable side effects in the patient. Post-operative radiotherapy is therefore often recommended. Thanks to developments in imaging and IT, the volume to be treated and the organs at risk are precisely defined, enabling the establishment (in 3 dimensions) of the radiation beams in such a way as to deliver a homogenous dose to the tumourous volume, while protecting the healthy adjoining tissues. In neuro-oncology, the technique of irradiation by TomoTherapy Hi-Art is mainly used to treat tumours at the base of the skull. This device on the one hand allows more targeted irradiation, and on the other very high precision treatment. Only some centres in Belgium, of which ours is one, have this device. Click here to learn more about Hi-Art.
The emergence of effective new chemotherapy agents in the treatment of cerebral tumours has radically changed the treatment of these cancers. These chemotherapies can be administered concomitantly with radiotherapy in the treatment of certain tumours, or as a supplement to them. Administration of these chemotherapies increases patient survival and also their quality of life.
Another revolution in the treatment of malignant tumours of the brain is the emergence of targeted therapies. Some medications specifically destroy tumourous cells by interacting with receptors shown on tumorous cells or their ligands (Anti-EGF). Other molecules specifically target the vessels which feed the tumours (Anti-VEGF).
Another development axis is the identification of genetic signature as factors in the prognosis and which are predictive of response to chemotherapy (MGMT methylation, chromosome loss: 1p19q).
RESEARCH
Research in oncology by the neuroradiological team in the medical imaging department applies mainly to two themes. The first is defining the best target for cerebral biopsy so as to guide the neurosurgeon’s movements and to be able to determine as precisely as possible the grade of tumour before treatment. The second theme is to clarify the therapeutic effects of surgery, radiotherapy and chemotherapy in the course of treatment, so as to adapt the treatment according to the results. In both these themes, perfusion images are at the centre of our research: magnetic resonance imaging of a thousand sections, gained in one minute to detect the degree of tumour neovascularisation.
