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- In 1975, the age-adjusted incidence of brain and other central nervous system (CNS) cancers, including cancers of the spinal cord, among adults in the United States was 5.9 per 100,000 persons. The age-adjusted incidence of these cancers among children age 19 and younger was 2.1 per 100,000. (Note: Age adjustment is a method of standardizing statistics to allow more accurate comparison of statistics obtained for different population groups.)
- In the same year, the age-adjusted rate of deaths (also called the mortality rate) from brain and other CNS cancers among adults was 4.1 per 100,000 persons; among children age 19 and younger, the rate was 0.9 per 100,000.
- Magnetic resonance imaging (MRI), which provides the resolution needed to optimally diagnose and plan the treatment of brain and other CNS tumors with surgery and radiation therapy, first became widely available in the 1980s.
- Clinical trials in the 1970s and 1980s showed for the first time that adding radiation therapy to surgery prolonged the survival of patients with glioma, the most common type of malignant brain tumor in adults.
- Chemotherapy was not a standard treatment for brain tumors because most early anticancer drugs could not cross the blood-brain barrier, which protects the brain from harmful substances. One class of drugs, the nitrosoureas, was found to cross the blood-brain barrier and, when combined with surgery and radiation therapy, was shown in clinical trials to produce a small but clear improvement in the duration of patient survival.
- In 2005, the age-adjusted incidence of brain and other CNS cancers among
adults was 6.5 per 100,000 persons; among children age 19 and younger, it
was 2.8 per 100,000. The higher incidence rates observed today are likely
due, in part, to an improved ability to diagnose brain and other CNS tumors
with advanced imaging technologies.
- MRI is now an accepted standard for imaging brain and other CNS tumors.
A newer technology called functional MRI, which measures changes in blood
flow that accompany brain activity, can be helpful in determining how well
brain regions are working, in assessing potential risk from surgery, and in
planning treatment. New intraoperative MRI machines can be used to monitor
the extent of tumor removal during surgery.
- The orally administered drug temozolomide, which first became available
in the United States in 1999 and belongs to a class of drugs known as alkylating
agents, can prolong the survival of patients with glioma when combined with
radiation therapy. High-dose chemotherapy regimens for the treatment of some
types of childhood brain tumor can delay the need for radiation therapy, possibly
reducing harm to the developing brain.
- Advanced radiation therapy techniques that target tumor tissue more precisely
and reduce radiation damage to surrounding normal tissue (such as three-dimensional
conformal therapy, stereotactic radiation therapy, and intensity-modulated
radiation therapy) are being refined.
- Researchers are exploring the use of other novel approaches such as targeted
therapy, gene therapy, immunotherapy, and vaccine therapy for the treatment
of brain and other CNS cancers.
- Scientists are beginning to understand the genetic complexity of brain tumors.
The Cancer Genome Atlas project has reported the first results of its large-scale,
comprehensive study of gene changes in glioblastoma (a type of glioma). The
Glioma Molecular Diagnostic Initiative has already made extensive genetic
and related clinical data from more than 500 glioma patients available to
researchers worldwide in a public data repository and bioinformatics work
space known as REMBRANDT. Our increasing knowledge of alterations in cell
signaling pathways in different types of brain cancer is helping researchers
design more effective treatments.
- The recent discovery (in 2003) of cancer stem cells in human brain tumors
has opened new avenues of research. Cancer stem cells make up only a small
proportion of the tumors that contain them, but are thought to drive tumor
growth and spread. Cancer stem cells may be more resistant to chemotherapy
and radiation therapy than other tumor cells, perhaps explaining why many
brain cancers are resistant to treatment.
- Despite tremendous advances in our understanding of brain cancer biology,
significant progress in our ability to diagnose and treat brain tumors, and
marked improvement in patients’ quality of life, the long-term prognosis
for most patients with brain cancer remains poor. Over the last 30 to 40 years,
the mortality rate for brain and other CNS cancers has remained largely unchanged.
- We will continue to explore the use of new imaging technologies for the
diagnosis, treatment planning, and follow-up care of patients with brain and
other CNS cancers. Promising new technologies allow doctors to measure the
volume of blood flowing through the brain. These measurements can be used
to better estimate tumor grade, size, and location before surgery. They can
also improve the ability to distinguish recurrent tumor tissue from damage
to brain tissue caused by radiation therapy, reducing the need for follow-up
surgical biopsies. Additional technologies that could be helpful in assessing
response to treatment measure tumor metabolic activity, tumor-cell proliferation,
and the amount of oxygen that reaches tumor cells.
- We will refine methods of delivering chemotherapy drugs and other agents
to the brain and CNS, such as developing drugs that have the ability to penetrate
the blood-brain barrier. Other delivery techniques, such as convection-enhanced
delivery, in which drugs or other anticancer agents are delivered under pressure
(convection) through a catheter inserted directly into or near a tumor, may
prove valuable.
- We will continue to refine radiation therapy techniques to further improve
the ability to deliver effective doses of radiation to malignant cells while
sparing the normal tissue.
- We will continue intensive research into the genetic changes that lead to
the formation of brain and other CNS cancers, which will yield new opportunities
for developing therapies that target these changes.
- We will expand our understanding of the role that cancer stem cells play
in the formation of brain and other CNS tumors and in their resistance to
treatment and use that knowledge to develop new treatments that target cancer
stem cell signaling pathways.
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