Technology
Transforming treatments for skull base brain tumours
Patrick Grover provides an insight into how focal radiation treatments have transformed the management of challenging brain tumours in recent decades, providing safer options for patients.
Although the majority of skull base tumours are benign and slow growing, they can be complex to treat and present a risk to brain function. The bones that form the skull base also form the eye socket, nasal cavity roof, part of the sinuses and the bones surrounding the inner ear. An abnormal growth here can put specific brain functions at risk, and so often warrant treatment. As these tumours form deep within the skull base, surgical excision can be difficult and requires a specialised team. There can be a risk of damage to the nerves and blood vessels surrounding the tumour, in some cases making surgery unfeasible. Treatments for brain tumours are regularly
advancing as developments in imaging and technology are integrated into modern medical practice. Focal radiation treatments such as Gamma Knife radiosurgery have transformed the management of these tumours over recent decades.
Non-invasive focal therapy Radiation can be delivered in different forms. The most focused and targeted is termed ‘stereotactic radiosurgery’. For well circumscribed, deep-seated tumours, this is the best option as this form of treatment can target a high dose of radiation to the tumour, while minimising any spread to the normal brain. This is because it uses up to 192 focused beams of gamma radiation which individually carry a low dosage and converge at a single point to deliver a high dosage of radiation, targeting the intended area only. One of the most common forms of stereotactic
radiosurgery is called ‘Gamma Knife radiosurgery’. This technique achieves the highest level of accuracy by using a stereotactic frame that is fitted to the head during the treatment. The other advantage of radiosurgery is that it is non- invasive, and therefore in some circumstances it avoids the need for open surgery. It is convenient and performed as a day case. However, it does have some limitations and cannot be used to remove a tumour that
is already causing symptoms. The aim is to arrest growth and, as a general rule of thumb, a tumour that is less than 3cm in size can be considered for radiosurgery. Smaller is better for this treatment type, as larger tumours can be susceptible to swelling reactions in the brain. Larger or more diffuse tumours may be considered more suitable for conventional ‘fractionated’ radiotherapy instead over a number of sessions of treatment. The majority of tumours, particularly those
of a smaller size, are suitable for treatment with stereotactic radiosurgery techniques such as Gamma Knife radiosurgery. As this has the benefit of being non-invasive, it has a lower risk of injury – for example, to the facial nerve, in the region of 1% of cases or less. Gamma Knife radiosurgery does not remove the tumour, but can help prevent further growth in approximately 95% of tumours, or more, depending on the size. There are risks of
exacerbating balance problems, for example, for a period of time, or accelerating hearing loss, but compared with ongoing tumour growth these side effects are usually well tolerated. Treatment is carried out as a day case, and normal activities including work can continue within a few days.
Treating large tumours For large tumours, especially those causing significant pressure on the brain resulting in symptoms, surgical removal performed by a highly experienced team is the preferred treatment. Depending on the location and critical structures involved, this may be a total or partial removal. With a total excision, the chance of recurrence in the future is extremely low. The pressure on the brain should be relieved with the prevention of further symptoms, and there is often improvement in existing symptoms. This improvement in symptoms
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Image provided courtesy of Elekta
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