Cancer is the uncontrolled growth of the body’s own cells. Cancer cells are malignant, which means that left unchecked they will invade and destroy adjacent tissues and organs.
They are also capable of metastasis (breaking away from the original tumour site and colonising distant sites in the body). Cancer is not a single disease, but is a generic term for over a hundred different types of malignancy.
It can develop from almost any type of tissue, and a single tissue can develop several different types of cancer. Cancers are classified according to the tissue and cell types from which they arise.
Primary brain tumours arise from cells within the brain itself, rather than developing from malignant cells that have migrated from a tumour elsewhere in the body.
They also very rarely spread outside the brain itself, although they often spread to other parts of the brain and often at some distance from the main tumour site. More than half of brain tumours are gliomas, that is, they arise from glial cells that make up supportive tissue in the central nervous system. There are several types of gliomas and one tumour often contains cancerous cells of more than one cell type. Gliomas, as with other types of cancer, are classified on a scale of I to IV (lowest to highest risk), according to guidelines set up by the World Health Organisation.
Brain tumours account for only about 1.5% of all cancers, and statistically speaking, are much less of a threat than some of the more publicised forms. Nevertheless, around 7000 people a year in the UK are diagnosed with brain tumours, making the brain around the tenth most common site for cancer in men, and the thirteenth in women. They are the third cause of death in males aged 15 – 54 years and the fourth cause of death in young women aged 15 – 34 years.
Brain cancer deaths in children exceed those of leukaemia, making it the second highest cause of death in this age group after accidents, and tumours like glioblastoma multiform, the most common and most aggressive type of primary brain tumour, are a significant cause of neurological morbidity and mortality in middle age.
Tragically, the majority of brain tumours are incurable, despite significant advances in treatment regimes. Unlike most other tumours, brain tumours have a tendency also to infiltrate surrounding normal tissue, making complete surgical removal virtually impossible. Current chemotherapeutic regimes are also very unpredictable because of the large variation in drug sensitivity between individual patients.
The traditional treatments of surgery, radiation and chemotherapy are therefore generally acknowledged to be merely palliative measures and offer a cure to only a small percentage of people, the five-year survival rate being 2 – 5%. Future strategies will focus on a molecular approach to the diagnosis and treatment of brain tumours.
Areas of particular interest are the development of potential therapeutic agents and targets in the signalling pathways related to glioma and meningioma, tumour immunolmodulaton, and the identification of prognostic and diagnostic serum biomarkers associated with the development of the disease.