Oligodendrogliomas
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 typically is not needed, although radiation therapy may be recommended in some cases. For a Grade III oligodendroglioma, surgery is often followed by radiation and/or chemotherapy.
Mixed gliomas have cells and characteristics of more than one type of glioma, usually astrocytomas and oligodendrogliomas (oligoastrocytomas).
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 typically is not needed, although radiation therapy may be recommended in some cases. For a Grade III oligodendroglioma, surgery is often followed by radiation and/or chemotherapy.
Mixed gliomas have cells and characteristics of more than one type of glioma, usually astrocytomas and oligodendrogliomas (oligoastrocytomas).
How Gliomas Are Evaluated and Graded
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.
Cells of Grade II tumors grow relatively slowly but show signs of change. Typically considered “pre-cancerous,” cells may begin to invade neighboring normal tissue, and if surgically removed, may return as a higher grade tumor.
Grade III tumors have actively reproducing cells lacking the structure and function of normal cells. They readily infiltrate adjacent normal tissue; it is not uncommon for recurrence at a higher grade after surgical treatment.
Grade IV tumors consist of rapidly reproducing abnormal cells and are able to form new blood vessels to sustain cells’ aggressive growth. Note:Oligodendrogliomas typically range from grade II to grade III.
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.
Cells of Grade II tumors grow relatively slowly but show signs of change. Typically considered “pre-cancerous,” cells may begin to invade neighboring normal tissue, and if surgically removed, may return as a higher grade tumor.
Grade III tumors have actively reproducing cells lacking the structure and function of normal cells. They readily infiltrate adjacent normal tissue; it is not uncommon for recurrence at a higher grade after surgical treatment.
Grade IV tumors consist of rapidly reproducing abnormal cells and are able to form new blood vessels to sustain cells’ aggressive growth. Note:Oligodendrogliomas typically range from grade II to grade III.
Treatments and Outcomes Vary by Individual Circumstances
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, including those researched at the Maxine Dunitz Neurological Institute are taking a proactive approach in fighting these tumors.
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.
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Causes & Risks
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, including those researched at the Maxine Dunitz Neurological Institute are taking a proactive approach in fighting these tumors.
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.
