Radiosurgery for brain tumours

Editor—Brada and Cruickshank criticise the use of radiosurgery in general and gamma knife radiosurgery in particular, apparently because of the lack of any controlled trials or robust case-control studies to show its efficacy.¹ Of course controlled trials are desirable, but if treatments are withheld until data from such trials are available then few, if any, neurosurgical operations or conventional radiotherapy treatments would be carried out. David Forster and his team at Sheffield have reported studies of gamma knife radiosurgery for otherwise inoperable arteriovenous malformations and for acoustic neuromas.² Is a controlled trial of radiosurgery needed when the end point is angiographically proved obliteration of the arteriovenous malformation or reduction of tumour volume as seen on magnetic resonance imaging?

To denigrate radiosurgery is misleading. Nor should it be a matter of choosing between open surgery or radiosurgery, because both methods can be used in concert. A large skull base meningioma can be reduced in size by open surgery to allow radiosurgery to be given to the difficult remnant, thus reducing overall morbidity for the patient.

A debate exists about the two methods of applying radiosurgery—the gamma knife and the linear accelerator³; certainly maintenance of the linear accelerator equipment is much more demanding, and the number of patients who can be treated per machine is lower than with the gamma knife. The linear accelerator, however, can be used with tumours elsewhere, whereas the gamma knife is appropriate only for intracranial lesions. Both methods are needed.

Brada and Cruickshank assert that radiosurgery for brain tumours is associated with a higher toxicity than that seen with conventional fractionated radiotherapy “without the assurance of long term efficacy.” This is misleading, for the two techniques are entirely different and have different objectives. Radiosurgery creates discrete tissue damage in one session—hence the term “surgery.” It is used to treat discrete abnormalities with well defined margins, unlike conventional radiotherapy.

More and better follow up studies are of course needed, but Brada and Cruickshank’s editorial does not convey reasoned information to doctors wishing to know more about radiosurgery. If I had a small acoustic neuroma, a deep arteriovenous malformation, a small but inaccessible skull base meningioma, or a solitary metastasis then I would prefer gamma knife radiosurgery to open surgery. I am impressed by its accuracy, simplicity, relative safety, and efficacy and the fact that it is virtually an outpatient procedure.