Like other forms of cancer, brain cancer is a complex disease that has several different cell types. Rates of survival are often influenced by the type of tumour a person has and by his age.
The medical community tracks cancer statistics according to the number of years a person remains alive after he or she has been diagnosed. According to the Central Brain Tumor Registry of the United States (CBTRUS), 28.8 per cent of adult males and 31.6 per cent of adult females are alive five years after their diagnoses. The CBTRUS, which lumps brain cancer together with other central nervous system cancers, includes statistics only for brain cancers that have occurred as the primary cancer site. They do not include brain cancers that are the result of cancer which originated elsewhere in the body but spread to the brain.
"The Merck Manual" states that gliomas are the most common type of cancerous brain tumour, accounting for 65 per cent of all primary brain tumours. Gliomas are so named because they are tumours that form in the glial cells of the brain. There are several different kinds of gliomas, and the survival rates vary widely depending on the type of glioma. According to the American Cancer Society (ACS), glioblastoma multiforme has the poorest five-year survival statistics, while oligodendroglioma has the best outcomes.
ACS reports that ependymoma tumours, which form in the brain's ventricle tissue, have the highest survival rates, but, according to "The Merck Manual," they account for a mere one per cent of all brain tumours.
Generally, younger brain cancer patients have better 5-year survival rates than older patients, no matter what type of brain cancer they have. The American Cancer Society provides a breakdown of 5-year survival rates by tumour type and age range.
Brain cancer causes nearly 25 per cent of all childhood cancer deaths (those occurring before age 20), according to the National Cancer Institute. However, survival rates improved an average of 1.1 per cent per year from 1975 to 1995 (the most recent period reported). The CBTRUS says the overall five-year survival rate for people younger than 20 is 66 per cent. (This statistic includes central nervous system tumours as well as primary malignant brain tumours.)
ACS emphasises that while survival numbers can be helpful, they don't necessarily serve as a gauge for an individual person's prognosis. "A number of other factors, including the size and location of the tumour and the amount that can be removed by surgery, can also affect outlook," says ACS.