Radiosurgery is the use of a special type of radiotherapy also known as stereotactic radiotherapy or Gamma Knife treatment. In this treatment careful computerised planning and a specially adapted radiotherapy machine are used to give very high doses of radiation to very small areas within the brain. Because the radiation is focused very precisely on the abnormal area of brain tissue there is virtually no damage to any of the surrounding normal brain and the treatment allows high doses of radiation to be given safely.

Two types of machine are used for this treatment, either a cobalt unit which, because it produces gamma rays, has often be called a 'gamma knife', or a modification of a normal linear accelerator (which produces a beam of high energy x-rays to kill the tumour cells).

Stereotactic radiotherapy has been used for some years to treat completely benign, non-cancerous, abnormalities of blood vessels in the brain and has been very successful. Its role in the treatment of secondary brain cancers is less certain but is the subject of much study and discussion at the present time.

When a primary cancer in another part of the body spreads to the brain it usually produces several new cancers, or secondaries, affecting several parts of the brain. Stereotactic radiotherapy would usually only be possible if there are three or fewer secondaries present and is only suitable for small tumours - usually about 4cm (one and a half inches) is the maximum diameter. Occasionally, if only a single secondary cancer is apparent an operation might be possible.

So far there have been no controlled clinical trials comparing surgery with radiosurgery in people with solitary brain metastases but it is thought that people treated with radiosurgery have a similar survival to those treated with surgical removal of the tumour. So radiosurgery is an alternative to surgery.  It has the advantages of not needing an operation and can be done on an out-patient basis.

For radiosurgery to be considered a number of other conditions would usually have to be met, including:

• the patient is reasonably fit and otherwise healthy
• there is no sign of uncontrolled cancer anywhere else in the body
• there has been quite a long interval between the time when the primary cancer was diagnosed and the appearance of the secondary cancer in the brain

If your husband's cancer fitted this picture then it is possible radiosurgery might be offered. This is still a very specialised technique, however, and currently in the UK is only available at some 13 hospitals, so some travelling for the treatment might well be involved.
Quite often if stereotactic radiotherapy is done then it is often followed by a course of 'normal' radiotherapy to the whole of the brain in case there are any other microscopic small seedlings of secondary cancer present which did not show up on the original scans.