What is stereotactic radiosurgery?
Stereotactic radiosurgery uses radiation delivered with the goal of submillimetre accuracy in order to maximise the dose of radiation given to a tumour without damaging the surrounding tissues. In order to do this, very exact patient positioning and treatment delivery is necessary. Using imaging scans, a team of doctors including a radiation oncologist, and often a neurosurgeon or a neurologist work together with a radiation physicist to pinpoint the position of the tumours and plan exactly how to treat it, keeping in mind the vital structures near the tumour which must be avoided.
What are the types of stereotactic radiosurgery?
There are three main methods used to deliver stereotactic radiation: Linac based stereotactic radiotherapy, Gamma Knife stereotactic radiosurgery, and proton beam therapy.
All types of stereotactic radiotherapy work in a similar manner, in that specialised equipment is used to focus many small beams of radiation on a tumour. Each beam has very little effect on the tissue it passes through but a high dose is delivered to the site where all the beams intersect.
During Gamma Knife stereotactic radiosurgery, a metal helmet/frame is fixated to the patient’s skull under local anaesthetic. The tumour is treated using focused beams of gamma radiation via pinholes in the helmet.
In Linac based stereotactic radiotherapy no frame is required. The patient is kept in position using a tight-fitting thermoplastic cast and a linear accelerator rotates around the patient’s head, delivering photon radiation in an arc. This is the technique used at Christiaan Barnard.
During proton beam therapy, no frame is required. The patient is positioned in the same way as in Linac-based treatment. However, instead of a Linear accelerator being used, a machine called a cyclotron is used to deliver heavy charged particles called protons. Proton beam therapy is not available in South Africa.
Why is stereotactic radiosurgery used?
Stereotactic radiosurgery is often used in the place of normal surgery to treat tumours that are located in surgically inaccessible areas of the body. It is also frequently used to safely treat tumours which are situated in close proximity to other critical structures.
Are there any side effects?
Fortunately, stereotactic radiotherapy generally has much fewer side effects than other forms of external beam radiotherapy. Because the treatment area is typically much smaller, less healthy tissue is affected by the radiation. A common side effect of the treatment is fatigue, so we recommend that you rest after your treatment session.
What does the treatment involve?
Before treatment begins, your doctor will perform CT or MRI scans to determine the size and location of your tumour, and to plan your treatment.
During the treatment session itself, you will be positioned on a treatment couch. You will be asked to remain completely still during treatment, a mask and/or other immobilisation devices may be used to assist with this.
You shouldn't feel any pain or discomfort during the treatment session, which generally takes between 30 and 60 minutes to complete.