What is an Oligodendroglioma tumour?
An Oligodendroglioma, sometimes referred to as an oligodendroglial tumour, is a rare, usually slow-growing tumour that forms from oligodendrocytes, which are a form of glial cell. It is more commonly diagnosed in adults rather than in children.
What is a glial cell?
Glial cells form a web of connective glial tissue to support the neurons (nerve cells) within the brain and spinal cord. Types of glial cells include astrocytes, oligodendrocytes and ependymal cells. Oligodendroglioma, astrocytoma and ependymoma brain tumours are therefore all classified as glioma tumours because they develop from glial cells, and in some cases a “mixed glioma” brain tumour may develop that contains a mixture of these different cells.
Historically, the classification of all brain tumours has been guided by how the tumour cells look when observed through a microscope (histopathological classification). This process is still very much in use today and provides a crucial starting point for understanding your individual brain tumour. Oligodendroglioma histology would indicate one of the following subgroups:
Oligodendroglioma Grade 1 is a low-grade or slow-growing form of brain tumour
Oligodendroglioma Grade 2 is also classified as a low-grade form of brain tumour.
Oligodendroglioma Grade 3 is a high-grade tumour, meaning that it grows quickly compared to a low-grade glioma brain tumour. It is also known as an anaplastic oligodendroglioma.
Oligodendroglioma Grade 4 would be reclassified as a glioblastoma multiforme (GBM) because it would be likely to include a variety of glial cells that had undergone a range of genetic changes.
It is now also possible to take a sample of your tumour during surgery or a biopsy procedure and test the genetic profile of the tumour, which gives a more accurate indication of a prognosis. As well as histopathological assessment, reports on the classification of suspected oligodendroglioma should include molecular markers such as:
IDH status – IDH stands for “Isocitrate Dehydrogenase”. This is an enzyme involved in the production of energy by brain tumour cells. Research has indicated that different forms of gliomas have differences between these enzymes, though their role in tumour initiation (how a tumour first begins) and tumour growth is still being explored. As part of this research, a number of drugs that can potentially influence IDH enzymes are being investigated.
1p/19q deletion – The word “deletion” refers to the fact that when you look at one of the chromosomes, the genes at positions 1p and 19q are missing. Tumours with a 1p/19q deletion are identified as oligodendroglioma tumours and may respond better to certain chemotherapy drugs, such as Temozolomide or Carmustine, than other tumours without the deletion.
MGMT methylation – This is tested for in all high-grade gliomas, which are grade 3 or grade 4. MGMT is short for O6-methylguanine-DNA methyltransferase and whether it is 'methylated' or 'unmethylated' indicates how effectively the tumour cells can repair the damage inflicted on them by certain chemotherapy drugs, such as Temozolomide. Patients with higher levels of MGMT methylation respond better to Temozolomide treatment. Methylation means the transfer of a methyl group (CH3) from one molecule to another, which affects the way the tumour behaves.
UK treatment pathways for oligodendroglioma can be found in the National Institute for Health and Care Excellence (NICE) guidelines and are summarised here.
Treatment for a low-grade oligodendroglioma
Surgery would be the first line of treatment. This enables a biopsy to be taken to confirm the diagnosis, and if the tumour is in an accessible place, as much of the tumour as possible would be removed.
After surgery, patients with no signs of any tumour left may be offered active monitoring: meaning no further treatment would be offered at this stage apart from scans every 3 to 6 months. Only when they were signs of the tumour returning or progressing would radiotherapy and chemotherapy be offered.
Patients whose tumours can’t be completely removed (for example, because complete removal carries a high risk of damage to surrounding healthy brain) will be offered radiotherapy followed by 6 rounds of PCV chemotherapy. This is a combination of the drugs procarbazine, CCNU (lomustine) and vincristine. Depending upon the molecular markers identified in the tumour, the chemotherapy drug temozolomide may also be considered appropriate.
Treatment for a newly diagnosed Grade 3 oligodendroglioma brain tumour
The first line of oligodendroglioma grade 3 treatment would be surgery, followed by PCV chemotherapy and radiotherapy. PCV chemotherapy is a combination of the drugs procarbazine, CCNU (lomustine) and vincristine. Depending upon the molecular markers identified in the tumour, the chemotherapy drug temozolomide may also be considered appropriate.
The order in which chemotherapy and radiotherapy would be given is decided based on discussions with the patient, taking into consideration factors such as the personal challenges of making multiple hospital visits and concerns around fertility. If you are concerned about fertility, radiotherapy would be given first.
Learn more about brain tumour treatments.
What causes an oligodendroglioma brain tumour?
A glioma brain tumour develops from cells that begin as neural stem cells. From this state they become progenitor cells, and then glial cells. When glial cells form a glioma tumour, damage can be seen in the DNA and they no longer undergo apoptosis, which means programmed or purposeful cell death. Apoptosis is an important process that enables our bodies to destroy cells that are faulty or at the end of their natural life cycle. When this process fails to happen, cells grow in an uncontrolled way and build up to form a tumour.
Discover more about risk factors for brain tumours on the ‘What causes a brain tumour?’ page of our website.
How can we find a cure for oligodendrogliomas?
Research we are funding across all of our Brain Tumour Research Centres will help lead towards finding a cure for oligodendroglioma brain tumours.
Our team at the University of Plymouth Low-Grade Brain Tumour Centre of Excellence are researching a range of mutations in brain tumour cells that initiate tumour progression and drive growth, transforming slow-growing low-grade gliomas into high-grade gliomas. Their discoveries are designed to enable new treatments to be developed and tested to halt and hopefully reverse this process.
Pioneering research at our Brain Tumour Research Centre of Excellence at Queen Mary University of London is focused on using glioblastoma multiforme (GBM) stem cells to help develop unique, patient-specific treatments that should also benefit those with other types of glioma brain tumours.
The team of research and clinical experts at our Centre of Excellence at Imperial College, London, are part of a global collaboration looking at how the ketogenic diet can influence GBM metabolism and help in the effective treatment and management of living with this brain tumour. They are also studying the influence of arginine deprivation on GBM cells and are working towards a clinical trial to investigate this further. They expect that their discoveries will also benefit other types of glioma brain tumours.
Scientists at our Centre of Excellence in the University of Portsmouth are looking at mitochondria in GBMs, exploring ways to ‘shut down’ these ‘batteries’ that supply energy to these and other types of glioma brain tumours. Find out more.
We also fund BRAIN UK at Southampton University, the country’s only national tissue bank registry providing crucial access to brain tumour samples for researchers from all clinical neuroscience centres in the UK, effectively covering about 90% of the UK population, and an essential component in the fight to find a cure for all types of gliomas.
How do I find a clinical trial for oligodendroglioma?
You can read about clinical trials and other research opportunities here on our website.