Gliomas
What is a Glioma?
Gliomas are primary brain tumours. They arise from the supporting cells of the brain. The two main types of gliomas are Astrocytomas and Oligodendrogliomas. Rarer types are Ependymomas and Choroid plexus tumours. Paediatric gliomas include Pilocytic Astrocytomas and Diffuse Intra Pontine Glioma (DIPG). Glioblastoma is the most common and aggressive type of Glioma.
What causes gliomas?
There is currently no known cause for Gliomas.
Past radiation exposure can give rise to these tumours. However, the vast majority of patients who have gliomas have never had significant radiation exposure.
Some people with certain genetic conditions also develop gliomas.
Where do Glioma’s occur?
Gliomas can occur in any part of the brain. Common locations are the temporal lobes and the frontal lobes.
What symptoms do they cause?
Gliomas can cause many different symptoms including (but not exclusively):
- Seizures (fits)
- Headaches
- Loss of use of your arm or leg
- Inability to speak
- Decreased vision, double vision
- Confusion
Sometimes Gliomas can be found incidentally on scans performed for unrelated symptoms.
What happens after I am diagnosed with a Brain Tumour?
Generally, with the onset of symptoms, you may have had a CT scan. The next step will be to have a MRI. This will give a more accurate picture of the tumour and other information about whether it is benign or malignant. Please see the section on the patient journey for more information.
How do we classify Gliomas?
Gliomas are graded according to the WHO criteria and are given a grade of 1-4. In addition to the grade, tumour tissue is now analysed from a molecular genetic perspective. This information helps us understand the tumour’s behaviour and can guide treatment.
What is the current recommended treatment for gliomas?
Pilocytic Astrocytomas (grade I) can often be cured by surgery alone.
On the other hand, at the present time there is no known cure for Grade 2-4 astrocytomas and oligodendrogliomas or glioblastoma.
Treatment is therefore aimed at controlling the tumour for as long as possible. There are three established methods as present.
- Surgery
- Radiotherapy
- Chemotherapy
Each of these treatments is administered by a different specialist. Ideally, these specialists should work together at the same hospital as a team to provide integrated care for the patient.
How is surgery done for Gliomas?
Surgery
Surgery for these brain tumours should ideally be performed by someone who subspecialises in the field of Neuro oncology and is part of a multidisciplinary team as described above.
Surgery is required in some form for all these tumours.
Biopsy
Surgery may just be to obtain some tissue to make a firm diagnosis. This is called a biopsy. It still requires a general anaesthetic and is usually performed through a small drill hole in the skull called a “burr Hole”. In order to locate the tumour, a technique known as stereotaxy is utilised. A needle is then passed through brain into the tumour to obtain some tissue. This tissue sample will then be analysed by a Pathologist to determine the exact diagnosis. Occasionally, the tissue obtained may not be of adequate quality to be analysed correctly. In this instance, further surgery may be required to obtain more tissue of better quality.
Surgery for maximal safe resection
Surgery may also be performed to remove as much of the tumour as possible. There is a good amount of medical evidence that states that radical surgery has the effect of lengthening survival. The aim of radical surgery is to remove greater than 95% of the tumour seen on the MRI scan.
Radical surgery may not always be possible. It depends on where exactly the tumour is located as to whether it can be achieved.
Radical surgery has become safer because of technological developments.
What if I don’t have surgery?
For some tumours, you might be advised not have any surgery and take a “watch and wait” course. This may be for a number of reasons including the location, the size and the symptoms it is causing. This involves close monitoring by your Neurosurgeon with regular MRIs. This may be the appropriate decision for low grade (grade 1 and 2) tumours.
However, there is a large body of medical evidence to state that radical surgery to remove as much of the tumour as possible is better for length of survival.
However, the only definitive way of diagnosing the type of tumour, is by obtaining tissue to analyse under a microscope. Without a tissue diagnosis, no other treatment can be prescribed. Therefore, for high grade tumours (grade 3 and 4) this is very important. Generally, with no treatment, these tumours will continue to grow and cause more symptoms and problems and eventually become life threatening.
How quickly do these tumours grow?
The growth rate of gliomas depends on the grade of the tumour.
Grade 1 tumours are slow growing and may only grow by 1-2mm per year.
Grade 2 tumours again are fairly slow growing and may grow by a few millimeters per year. However, grade II tumours can very suddenly change and start to grow more rapidly.
Grade 3 tumours are malignant and grow significantly over months.
Grade 4 tumours are very rapidly growing and tend to grow quickly over a matter of days or weeks.
What other treatments are available?
Radiotherapy
Radiotherapy is administered by a specialist known as a Radiation Oncologist.
Radiotherapy is the crucial next step after surgery for Grade III and Grade IV astrocytomas, oligoendrogliomas and glioblastoma. The need for radiotherapy for grade 2 astrocytomas and oligodendroglioma is more controversial. It appears to delay recurrence and transformation into a grade 3 but does not seem to lengthen overall survival.
Chemotherapy
Chemotherapy is used inconjunction with radiotherapy. The drug most often used is Temozolomide. Chemotherapy is prescribed and supervised by a Specialist Medical Oncologist. For more information contact your Medical Oncologist
Targeted therapies
We are now moving into the era of targeted therapies. These are specially designed molecules that target specific genetic mutations or specific cellular functions within tumour cells. There are many of these drugs in current use for a lot of other cancers. However, at present there is only one targeted therapy for IDH mutant low grade gliomas - vorasidenib. Others can be accessed through clinical trials. Please discuss this further with your surgeon or oncologist.
Vaccines
Vaccines are treatments that use the patient’s own immune system to fight the tumour. These can be targeted molecules that enhance certain cells in the immune system. Alternatively, tumour tissue obtained at surgery may be used to stimulate the patient’s own immune system to fight the tumour. Vaccines are also only available currently on a trial basis.
