Malignant Brain Tumors
Gliomas: Malignant Tumors Originating in the Brain
The term “brain tumor” encompasses a wide range of tumors growing from many different types of cells; each type of tumor has individual characteristics. Many aggressive and challenging brain tumors grow from glial cells (or glia). Glial cells act as scaffolding and glue to hold, nourish, insulate and protect neurons, the brain cells that send and receive electrical impulses responsible for neurologic function.
Brain tumors arising from glial cells are called gliomas. Because there are different types of glial cells there are different kinds of gliomas, including:
Astrocytomas can occur anywhere in the brain but are most commonly located in the cerebrum, the largest part of the brain where higher brain functions such as thought and movement are processed.
This type of tumor arises from astrocytes, star-shaped cells that play several roles in the brain. Astrocytes are supportive components of the brain’s “white matter,” the tissue containing the electrochemical “transmission lines” that connect nerve cells. Astrocytomas are found in both adults and children (see pediatric astrocytomas).
Because they can grow very slowly, certain low-grade astrocytomas may need nothing more than close observation. Others will be removed surgically and have little if any effect on longevity and quality of life.
Higher-grade astrocytomas typically require surgery, when possible, chemotherapy and/or radiation therapy. Grade IV astrocytomas are also called glioblastoma multiforme, which is the most aggressive type of brain tumor.
Astrocytomas can occur as Grade III and Grade IV tumors at the outset. Many, however, arise from pre-existing Grade II astrocytomas that progress to a higher grade in four to five years.
Comprising 19 percent of all primary brain tumors, glioblastoma multiforme is the highest-grade glioma (Grade IV) and most malignant form of astrocytoma. Glioblastoma multiforme can be diagnosed at nearly any time in life but incidence increases in middle age.
Gioblastoma tumors are able to extend their reach into adjacent tissues and form “satellite” tumors at distant sites within a patient’s brain.
Cedars-Sinai scientists have conducted extensive research into gioblastomas and developed innovative, experimental approaches to treatment. Several clinical trials are now underway.
The brain and spinal cord are bathed in cerebrospinal fluid contained within ventricles of the brain and the central canal of the spine; ependymomas grow from ependymal cells that line these structures. Ependymomas make up about six percent of intracranial gliomas and about 60 percent of all newly diagnosed spinal cord tumors.
Ependymomas are more common in females than males and in children than adults (see pediatric ependymomas). Although average age at diagnosis is 22, there are peaks at ages 5 and 34. In adolescents and adults, many low-grade intracranial Ependymomas, including those occurring in a patient’s spinal cord, can be completely removed surgically without long-term consequences. Higher-grade tumors tend to be resistant to treatment.
Oligodendrogliomas are slow-growing transformations of oligodendrocytes; cells that wrap around axons, the fibers that carry electrochemical signals from neurons. Oligodendrocytes maintain “insulation” that enhances the transmission of signals.
Oligodendrogliomas make up about three percent of primary brain tumors; they usually occur in young adults and range from Grade II to Grade III. Because oligodendrogliomas are less likely than other gliomas to spread into normal brain tissue, surgery alone is frequently very beneficial. When complete surgical removal of a Grade II tumor is possible, additional therapy usually is not needed, although radiation therapy may be recommended in some cases. For a Grade III oligodendroglioma, surgery is usually followed by radiation and/or chemotherapy.
Mixed gliomas have cells and characteristics of more than one type of glioma, usually astrocytomas and oligodendrogliomas (oligoastrocytomas).
When a brain tumor is detected, treatment decisions will be based on a variety of factors, including the risk posed by the tumor’s aggressiveness.
Primary brain tumors – those that originate in a patient’s brain – are categorized according to a standardized four-level scale developed by the World Health Organization. Grade I represents the least aggressive and Grade IV the most aggressive tumors.
Grade I tumors consist of slow-growing cells similar to normal cells in appearance. If treated at this stage, the outlook for long-term survival is usually good. Grade I tumors are rare in adults.
In general, younger patients tend to have better outcomes because their immune systems are stronger, but malignant gliomas are most often diagnosed in people who are middle-aged or older. Patients undergoing standard treatment for the most aggressive gliomas currently have an average length of survival of 15 months. It is important to remember, however, that some patients live considerably longer, and new experimental therapies are taking a proactive approach in fighting these tumors.
(Quote – hopeful/cutting edge)
For the majority of high-grade gliomas (grades III and IV) and many low-grade gliomas, surgical removal – when possible – will be the first step in treatment. Not all patients are healthy enough to undergo surgery, and some tumors are situated in inaccessible locations or have spread so extensively that surgery may not be an option. Also, gliomas typically have a soft texture and irregular shape, with projections extending into healthy brain tissue, making them especially difficult to treat. Some microscopic tumor cells inevitably remain even after the most successful surgery, but overall treatment effectiveness and length of survival are generally found to be better when “image-complete resection” – the removal of all tumor cells visible on MRI – can be achieved.