Radiotherapy techniques for intracranial tumours

The central nervous system (CNS) consists of the brain and the spinal cord. CNS tumours are relatively rare (<2% of all cancers and cancer deaths). Their incidence with age has two peaks, one in childhood (5-9 years) and the other >50 years where it increases with age. They can be malignant or benign. Even benign tumours can be critical due to their location in brain tissue (e.g., compressing the surrounding tissue) and possibly fatal. Radiosensitivity differs among CNS tumours, e.g., high-grade gliomas are generally radioresistant while medulloblastoma is more radiosensitive. Radiotherapy (RT) is usually given following surgery and can be radical (with curative intent) or palliative (to relieve symptoms). For instance, treatment of CNS germinomas and medulloblastoma is likely to be curative while only short-term palliation is achieved with high-grade astrocytomas. The majority of CNS tumours develop within the brain. Figure 1 shows a schematic classification of intracranial tumours according to site. However, some tumours, e.g., medulloblastoma, ependymoma, germinoma and CNS lymphoma can spread to the spine via the cerebrospinal fluid pathways. In this paper, RT of intracranial tumours will be reviewed briefly with more emphasis on the methods that have been developed and/or used at the Royal Marsden Hospital, UK.