Over recent years the use of radiosurgery has expanded beyond just the treatment of cancer. KATHLEEN ARMSTRONG reports
RADIOSURGERY is a radiation delivery-based procedure traditionally used to treat small, defined tumours in the brain. It works by giving a high dose of radiation to targets in a single dose and is used to treat a range of tumours, including acoustic neuromas of less than 3cm, secondary brain tumours, pituitary adenomas, and haemangioblastomas. It is also used for non-cancerous conditions such as arteriovenous malformation (AVM).
However, over recent months and years its use has been expanded to treat tumours in other parts of the body, including lung, prostate, spine and pancreatic tumours and functional disorders such as trigeminal neuralgia or Parkinson's tremors/rigidity.
And its application does not stop there, with interest growing in broadening the application of radiosurgery.
A type of stereotactic radiotherapy, radiosurgery technology comes in three main types. The first, and oldest, is Cobot 60-based technology, the most well-known of which is the Gamma Knife from Elektra.
The Gamma Knife was first developed by Swedish neurosurgeon, Lars Leksell, in the 1950s. Patients are placed with a head frame fitted under local anaesthetic for the minimally-invasive treatment, holding their head still while the radiation is being delivered. This allows the treatment to be delivered with more accuracy. However, it can also inhibit the ability of the machine to reach some more-challenging tumours, such as those located below the base of the skull. To resolve this, Elekta developed the Extend programme, which furthers the application of Gamma Knife surgery, working alongside the latest generation technology, the Leksell Gamma Knife Perfexion.
Clinical trials are currently underway in the US testing the use of Gamma Knife radiosurgery for the treatment of temporal lobe epilepsy, as an alternative to temporal lobectomy surgery. The use of radiosurgery is also being explored for the treatment of chronic cluster headaches.
A second type of radiosurgery is the linear accelerator. The treatment is delivered without the need for a head brace as it moves with the patient to deliver its radiation beam. The main technologies of this kind are Accuray's CyberKnife and the Varian and Brainlab Novalis Tx radiosurgery platform. The CyberKnife was developed in 1987 by Dr John R Adler, a professor of neurosurgery and radiation oncology at Stanford University Medical Center. Using a robotic arm, the technology X-rays the patient before the delivery of each radiation beam and compares the location of the tumour with results of a CT scan taken before the treatment. This allows it to take into account any movement by the patient.
The Varian Novalis Tx is a stereotactic linear accelerator platform which allows treatment to be given in 30 minutes or less. A range of new stereotactic body radiation therapy (SBRT) protocols developed for the lung and liver were presented at the Novalis Circle's international conference in November 2010. This included a new protocol delivered by Dr Bin Teh, vice chairman of the Department of Radiation Oncology at The Methodist Hospital in Houston, Texas. The procedure involves the use of fractional SBRT to control primary, recurrent and metastatic lung cancers.
"For the first time in 50 years, we have a new treatment option - F-SBRT - that can positively impact patients living with primary or metastatic lung cancers," Dr Teh told the conference.
A new SBRT treatment protocol for the liver was also introduced at the Novalis event by Dr Percy Lee, a radiation oncologist at the University of California - Los Angeles (UCLA) Jonsson Comprehensive Cancer Center. The treatment protocol, which incorporates chemotherapy, not only controls tumours in the liver, but also reduces complications after liver transplantation.
For the first time in 50 years, we have a new treatment option that can positively impact patients living with primary or metastatic lung cancers
"In the past, physicians hesitated giving patients awaiting liver transplants radiation treatment, because a broad application was considered far too toxic," Dr Lee said. "Using Novalis Radiosurgery we can deliver very high doses of radiation to precise locations in the liver, minimising liver toxicity and controlling tumour growth. By minimising toxicity, patients are able to maintain their health and are more likely to be considered candidates for liver transplantation."
The third type of treatment - proton, or particle, beam radiosurgery - is still relatively new and there are only a few centres around the world delivering the therapy. In the UK, there is currently only one centre - the Clatterbridge Centre for Oncology NHS Foundation Trust. In the Douglas Cyclotron Unit, the Clatterbridge Centre provides treatment for cancers in the eye, including choroidal melanomas, choroidal haemangiomas, iris melanomas and conjunctival melanomas. It works by sterilising the tumour cells so that they can no longer reproduce. However, the application of proton beam therapy is much broader and in other parts of the world, such as the US, proton beam therapy is currently being used to treat prostate, lung, eye and other cancers. Clinical trials are also underway to assess its use in a range of other treatments, including early stage breast cancer and liver cancer.
Using Novalis Radiosurgery we can deliver very high doses of radiation to precise locations in the liver, minimising liver toxicity and controlling tumour growth
In October 2010, the Coalition government announced that it was investing £43m to increase access to proton beam therapy for high-priority patients.
"This £43m will be used to treat patients abroad," the Government said. "We're already looking at building a unit here, but that will take time and is a decision for the next spending review period."
The Government says the £43m will have benefited around 400 patients a year by the end of the current spending review period.
The uses of radiosurgery are constantly expanding as the technology is refined and clinicians discover new treatments. Its precise delivery means less damaged tissue and quicker treatment time for patients - cutting edge in more ways than one.