Glioblastoma Multiforme (GBM) Radiotherapy

Glioblastoma Multiforme or GBM, is a high grade tumour that arises from the brain and can invade within the brain but does not spread to elsewhere in the body. It is aggressive and tends to arise and progress quickly. Unfortunately, this has a significant impact on the person as it is a brain cancer. Normal work, social and family interactions deteriorate and sufferers of GBM become increasingly reliant on caregivers as time passes.

The diagnosis is first suspected after symptoms such as seizures, headaches, stroke-like weakness, speech disturbance or a change in personality are investigated, usually with an MRI brain scan. A tissue sample confirms the diagnosis. A neurosurgeon will perform this and the extent of the operation may vary from a small sample called a biopsy, a subtotal resection where some but not all the tumour is removed as safely as possible and, in some cases, a gross total resection is done where all visible tumour is removed. The extent of surgery depends on the amount of tumour and its location, as sometimes not all visible tumour can be removed safely. Unfortunately, there is always microscopic disease that is left behind despite the best operations, hence further treatment is required. This will be radiotherapy with likely addition of chemotherapy, or chemotherapy alone.

The next step is to check the tissue for further molecular and pathological features that might need to be addressed by the treating clinicians. There may be a need for recovery from the surgery with rehabilitation and for the operation wounds to heal before further treatment. Typically, 3 to 4 weeks may be needed for this. The robustness of the person with GBM will need to be assessed prior to considering any further treatment. I use ECOG status as a more objective measure of performance status.

There are numerous options for radiotherapy and this is best discussed with the treating radiation oncologist. More standard regimes range from 1 week, 3 weeks or 6 weeks of radiotherapy. This treatment requires a planning CT scan and a mask to be custom fitted over the head so the treatment can be accurately delivered. It is usually delivered 5 days a week and may typically last from 10 to 20 minutes depending on the complexity of the plan.

There are a number of common side effects that can occur with treatment and this can include tiredness, scalp hair loss, and headaches amongst others, usually towards the completion of the radiotherapy or soon after. Ongoing permanent side effects than can occur include poorer short-term memory and difficulty concentrating as well as others. The severity and range of side effects depends on the specific features of the tumour and treatment and the underlying preexisting features of the person with GBM.

Chemotherapy may be an option as well. This can be alongside the radiotherapy or by itself. The most standard chemotherapy is an oral tablet called temozolomide. Further cycles of chemotherapy may be given after the initial radiotherapy as well for several months. This chemotherapy does require at least weekly blood tests to ensure it can still be taken safely. The common side effects from temozolomide includes nausea and vomiting, an increased risk of bleeding, a weakened immune system and risk of severe infections. There are others as well which can be discussed with your clinician.

Some cancer centres in certain countries may also offer another treatment called tumour treatment fields. These are transducers, which are placed on the scalp and deliver electric fields of different frequencies to the brain.

Glioblastoma is a devastating disease with no cure as yet, but research continues. If you would like to know more on GBM and its treatment, other websites I can recommend include the Targeting Cancer, and EVIQ websites. I hope this information helps you and do recommend you clarify any concerns or further questions you have with your oncologist.

© Ramesh Pandey March 2025