A glioma is a common type of brain tumor that originates in the glial cells of the brain. These cells form the tissue that surrounds and supports neurons in the brain.
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An overview of gliomas
Gliomas account for around 33% of primary brain tumors. This type of brain tumor can affect an individual at any age, although it is more common among adults and slightly more common among men than women.
The treatment approach to gliomas depends on their size, location, and grade. Sometimes, the glioma is very slow growing (low grade) and may not require treatment unless it starts to grow more quickly or cause symptoms.
High-grade gliomas, on the other hand, are fast-growing and aggressive tumors that may require treatment with a combination of surgery, radiotherapy, and chemotherapy. Those with high-grade tumors generally have a poor outcome due to the high rates of recurrence.
The techniques typically used to diagnose gliomas include assessment of medical history and symptoms, a neurological exam to test balance, reflexes, vision, hearing, and cognitive ability, magnetic resonance imaging (MRI) and/or computed tomography (CT) scans to create detailed images of the brain, as well as a biopsy to test small samples of the tumor under a microscope.
Aside from the grade of the brain tumor, the treatment a person receives will also depend on the following factors:
- The amount of the tumor can be surgically removed
- Age
- The position of the tumor
- The effects of the tumor on overall health and wellbeing
The treatment for gliomas involves a team of individuals from multiple disciplines including neurosurgeons, radiotherapists, neuro-oncologists, and pathologists.
Low-grade gliomas
Monitoring
As low-grade gliomas can sometimes grow very slowly, treatment may not be required immediately after the diagnosis, unless the tumor is causing symptoms.
Therefore, a patient with a low-grade glioma is initially monitored through the use of MRI scans to assess how quickly the glioma is growing. This is referred to as “watchful waiting.” In cases of very slow-growing tumors, treatment may not be necessary until months or years later and, in some older individuals, the tumor may grow so slowly that treatment is never required.
Understanding Low Grade Gliomas Video - Brigham and Women's Hospital
Surgery
If the tumor does start to grow more quickly, surgery may be of significant benefit to patients. Overall, about 50% of patients with low-grade gliomas can expect to need surgical intervention within two or three years of their diagnosis.
The surgical removal of glioma will involve the surgeon taking as much of the tumor as is safely possible in a process referred to as “debulking.” If it was possible to completely or almost completely remove the tumor, no further treatment may be required, although the patient will still need regular monitoring through MRI scans.
In some cases, adjuvant radiotherapy may be required. This is more likely when the following factors apply:
- Age over 40
- A large amount of tumor remaining after surgery
- The presence of symptoms such as weakness in a region of the body
Outlook
The outlook after surgery for gliomas that were slow-growing is generally positive, even in cases where some of the tumors cannot be fully removed. Slow-growing gliomas can take many years to start causing symptoms again. In fact, almost 50% of patients with low-grade gliomas that were only partially removed still live for at least 10 years after they have undergone surgery and radiotherapy.
High-grade glioma
Surgery
For the very fast-growing high-grade gliomas, treatment will typically involve surgery to remove as much of the tumor as possible. In some cases, radiotherapy and/or chemotherapy treatments may also be recommended after the surgical removal of the tumor.
Radiotherapy
Although radiotherapy cannot cure gliomas, it can be used to control the tumor for as long as possible. Radiotherapy is typically carried out for five consecutive days each week, over a period of a few weeks.
For those with generally poor health status, the radiotherapy course may be shortened and only last for two weeks. The radiotherapy slows tumor growth, thereby delaying disease progression and the development of symptoms.
Chemotherapy
In cases of high-grade glioma where at least 90% of the tumor can be surgically removed, a small chemotherapy implant referred to as carmustine may be put in place during the operation. Although this implant can improve survival, the therapy is associated with uncomfortable adverse effects.
For those with a generally good health status, chemotherapy capsules called temozolomide may be used after surgery for several months and in combination with radiotherapy. Alternatively, a physician may decide to keep temozolomide in reserve as a treatment option that they can apply if the tumor starts to grow more quickly. Chemotherapy is successful in shrinking or controlling tumors in around one-third of people after they have undergone surgery.
New therapies
Some examples of therapies that are currently being developed for the treatment of gliomas include gene modification and oncolytic virus therapies. For the latter, retroviruses and adenoviruses are used to carry targeted drugs directly to cancer cells which are then destroyed, while sparing any healthy surrounding cells.
References
Further Reading
Researchers introduce CRISPR-mediated genome and cancer shredding as a conceptual paradigm to treat recurrent gliomas