What is Gamma Knife radiosurgery

Gamma Knife radiosurgery (GKS) is a safe, effective and non-invasive procedure that uses radiation to treat conditions in and around the brain. It is sometimes used as a replacement for conventional surgery, but at other times it may be effective in situations where there is no conventional surgical alternative available. Radiation treatment is delivered with great precision to abnormal tissue within or around the brain, whilst at the same time minimising any dose to surrounding healthy tissue. The name 'Gamma Knife' is in some ways misleading - no knife or cutting implement is actually involved at any stage. The term 'Gamma Knife' is intended to convey the idea that this radiation treatment is in some ways delivered as though it were an actual knife, because it offers a similar sort of precision and targeting to that offered by actual surgery. Indeed it uses radiation in much the same way as a surgeon uses a knife.

How does Gamma Knife Work?

Radiation damages the DNA in the cells of the tumour or other abnormality being treated, such that the cells that make up the abnormal tissue targeted can no longer reproduce. Eventually, when these cells come to the end of their natural life span, they find that they are unable to reproduce and replace themselves because the DNA essential to this process is no longer functioning properly. It follows that tumours that naturally grow quickly will be more rapidly destroyed by GKS than those which are more indolent - and indeed this is what we observe. Some lesions which are very inactive in terms of cell function may take up to 2 or 3 years or more to respond to treatment -this is typically the case for instance with blood vessels, and arteriovenous malformations (see below) usually resolve over this sort of time period.

Is Gamma Knife radiosurgery safe?

Yes - in terms of the risk of damage to tissue around the target area. Having said that, as with any form of surgical or radiation treatment, there will always be some small risk attached and this can never be reduced to zero. However, in the case of GKS this can nearly always be brought down to very low levels - indeed one of the more common reasons for recommending GKS is that the overall risk compared to open surgery is frequently much lower. This is sometimes so much the case that the surgical alternative may actually carry a higher overall risk than that of the condition being treated, thereby rendering it effectively inoperable other than by radiosurgery. The precise nature and magnitude of any risk will vary with the size, nature and position of the lesion being treated. You should ask your treating doctor to elaborate on the details of this with respect to your own individual situation - he will be more than happy to give you a very full explanation of all that is involved.

Is Gamma Knife radiosurgery effective?

Yes. GKS has now been used worldwide for about 40 years to treat benign and malignant tumours. It has also been used to obliterate arteriovenous malformations (AVM) and in the treatment of some other disorders including trigeminal neuralgia and some forms of epilepsy. During this time period the results of many thousands of treatments have been published in papers in the medical literature, and the efficacy of GKS is indeed thoroughly well established and accepted. For many conditions a success rate well in excess of 90% can now be confidently predicted, though this is not necessarily the case for all such conditions. As above, you should ask your treating doctor to elaborate on the details of this with respect to your own individual situation.

Furthermore, patients are usually still suitable for GKS even if they have previously undergone conventional neurosurgery, radiation therapy, chemotherapy, or (in the case of an AVM) an embolisation procedure.

What are the possible complications of Gamma Knife radiosurgery?

Serious complications of GKS are really very unusual. Minor side effects, which generally resolve within a few hours, are sometimes seen and do not usually present the patient (or the doctor!) with a significant problem. It is fair to say that the large majority of patients suffer no side effects whatsoever, apart perhaps from a feeling of being a bit tired and 'washed out' at the end of a busy day's treatment!

We tend to think of complications in terms of those which may occur early i.e. soon after treatment, and those which can occur at a later stage, perhaps some weeks or months following GKS:

Early Complications:

• Common:
Some local discomfort of the scalp relating to the pin sites which are used to fix the frame - resolves within a few hours, almost certainly by the following morning.

Headache - again usually mild, resolving rapidly.

Mild nausea.

• Rare:
Skin reddening and irritation.

Epileptic seizures - in susceptible patients.

Swelling of surrounding brain tissue.

Delayed Complications:
• Common:
None

• Uncommon:
Visual Loss, Hearing loss, Epileptic seizures, Radiation effects on surrounding brain tissue. Hair loss (very localised) adjacent to treated area. These complications tend to relate only to treatment for particular conditions - (see the relevant sections under 'diagnosis text' [below] for details pertaining to particular tumour/problem).

 

What are the potential benefits of Gamma Knife radiosurgery over conventional surgical techniques?

Benefits May Include:

• The risks of infection, haemorrhage and spinal fluid leakage are eliminated, as is the scarring and potential disfigurement that results from conventional neurosurgery.

• The small risk associated with general anaesthesia is also eliminated. A mild sedative is occasionally used.

• GKS usually only involves a single night's stay in hospital, and frequently not even that, as opposed to the extended stay often necessitated by surgery.

• GKS can be sometimes be used in conjunction with conventional surgery, usually taking the place of the more risky component of the latter. In other words, where conventional surgery is absolutely required, its risk can be reduced by partially substituting GKS as a ''boost'' to perform the final part of the job.

• An individual who might be a relatively high risk candidate for conventional surgery may be a much safer candidate for GKS.

• Efficacy when prior surgery or radiation therapy has failed to control the disease - hormone secreting pituitary gland tumours might be a particularly good such example.

• Unlike conventional whole brain radiotherapy Gamma Knife radiosurgery is directed very specifically at the target. This spares most of the adjacent normal brain tissue from exposure to unnecessary excess radiation.

• ''Fractionation'' is not required - unlike conventional radiotherapy which is often delivered in many fractions over several weeks, GKS can nearly always be delivered as a single treatment over the course of less than a day. Multiple hospital visits are therefore avoided.

• As a day case treatment GKS offers the prospect of return to work, driving, and other normal social activities within a few days in the vast majority of cases. This is frequently as soon as the day following treatment.

• Established effectiveness over 40 years of experience worldwide, with a very low rate of complications.

Will the Gamma Knife procedure hurt?

The stereotactic frame is fitted under local anaesthesia. This involves the administration of 4 small injections around the circumference of the head, in order to numb the sites where the 4 pins are to be used to secure the frame. The experience of these is the same as when visiting the dentist for the purpose of having a tooth put to sleep for filling or whatever. Indeed the same local anaesthetic drug is used in both instances. Very quickly, after a brief stinging sensation, these areas will go numb. The frame is then attached. As the pins are secured you will feel a strange "pressure" sensation which quite soon passes off. The whole procedure takes about 5 - 10 minutes, and after the frame is fitted you will gradually get used to the sensation. After a short while you will no longer feel this, and you will almost forget that the frame is there at all! Frame fitting undoubtedly involves a small degree of discomfort, but most patients tolerate it remarkably well, and tend to comment that it was much preferable to the idea of having a major surgical procedure performed. At the end of the procedure the frame is removed. This only takes a minute or two, and is really not at all traumatic.

Will I be radioactive?

No. All radiation stays within the treatment room. The Gamma rays used in the treatment do not remain in the body.

Will I have any swelling or oedema?

In the postoperative period some tumours can swell a little as a result of their being injured by a dose of radiation. This may be manifest as a slight increase in apparent size of the tumour as assessed by MRI or CT scanning at about 6 - 9 months post treatment. This appearance must not be misinterpreted as tumour growth. It is self-limiting, and will soon be followed by reduction back to original size, or even smaller. If this temporary swelling (which is actually indicative that the treatment is starting to work) causes any symptoms, then a short course of steroids or other medication is sometimes used to treat the swelling.

Will I lose my hair?

The vast majority of patients have no risk whatsoever of losing any hair at all. Furthermore, even in those few cases where hair loss is a possibility, such hair loss will never involve the entire scalp - as typically happens with conventional whole brain radiotherapy. Only a small number of patients will have tumours sufficiently close to the scalp to carry the risk of any hair loss at all. If a lesion to be treated is very close to the inside of the skull, it is possible that enough radiation will be delivered to the scalp such that a patch of hair may be lost. This hair usually grows back, though it may be a little lighter in colour and finer in texture than previously.

Can Gamma Knife radiosurgery cause another tumour?

Theoretically yes - all forms of radiation can in principle cause tumour formation - but instances of this actually happening in real life are so rare that we haven't even been able to measure such a low risk number. There are some individuals (with rare conditions) who are at risk from developing further tumours because of their underlying condition, and very occasionally (perhaps a dozen times out of tens of thousands of patients over several decades), such new tumour formation has been reported. Based on existing experience, the incidence of radiation caused tumours is extremely low

How will I feel following treatment?

Most patients feel just as well as they did at the beginning of the day. Some tiredness is quite common, especially if the treatment has occupied most of the day. A little discomfort at the pin sites and a mild headache are also quite common - this may persist for up to a day or two. Mild nausea may also occur during the first 48 hours following treatment. For these reasons we like to keep most patients in hospital overnight for a few hours observation, and mild anti-nausea and headache medication is routinely prescribed for patients who may require it - nearly everyone is fit to be discharged home by 10 or 11 o'clock the following morning, and a sizeable number of patients don't even require an overnight stay.

Following treatment when can I go back to work?

As soon as you feel well enough. There is no reason why you should not go back to work the following day - some patients have even been known to return to work later the same day, but you should not feel pressured to be quite so valiantly stoical! It is fair to say that most people return to work within less than a week.

Following treatment how soon can I travel (by motor vehicle / bus / train / plane)?

Again, as soon as you feel well enough. There is no reason why you could not travel the following day, or even some time later on the actual day of treatment.

When will I see an improvement or know if the treatment has worked?

Generally the effects of GKS are manifest gradually over many months, in some cases even up to 3 or 4 years. This is one of the reasons for an annual review (at least) of each case. Some lesions gradually resolve and eventually disappear altogether, while others simply stop growing - this is frequently all that is required in order to pronounce treatment as successful. In a few cases, where the aim is to stop intractable pain, some relief may occur in the hour following treatment. However, beneficial effects in this situation usually take about 4 to 6 weeks following treatment to become apparent.