Introduction to HIFU

What is HIFU?

High energy, high frequency, focused sound waves (High Intensity Focused Ultrasound, or HIFU) allow the destruction of a precise volume of tissue within an tumour without harming surrounding structures. The newly available, advanced equipment used for this is the HAIFU JC model. Its HIFU beam heats and so destroys a very precise volume of tissue at its focus, and can be used to treat a large number of different tumour types. It is one of the first machines of its kind to be used clinically and made available commercially. Previous studies, using a similar research device at the Royal Marsden Hospital for the Institute of Cancer Research, have shown that focused ultrasound is safe and has minimal or no side effects, and can offer advantages over existing treatments.

Small tumours can generally be destroyed in one session, but large tumours may require more than one session. There are advantages in some cases to combine HIFU with other medical treatments. It is normal to follow up the HIFU treatment with one or more MRI scans to confirm the destruction of the tumour.

What are the side effects of treatment?

There is no evidence of side effects of diagnostic ultrasound. With HIFU there have been occasions when the skin has been affected by the equivalent of a mild sunburn, which clears up in a matter of days.

Initially patients treated by HIFU without anaesthetic reported discomfort during treatment The use of anaesthetic has eliminated this problem and also helps to keep the patient still during treatment. Some discomfort is felt after treatment by some patients, but this is generally mild, rarely lasts more than a few hours and can be easily controlled with standard pain relief tablets. It has been reported that there is a very small risk of an infection in the area that has been treated, which can be simply dealt with by antibiotics.

There is a risk that healthy tissue can be damaged by HIFU. However, the HAIFU JC Model enables precise pre-treatment planning and tumour targeting, which minimizes this risk.

There is no evidence that HIFU can lead to the spread of a tumour. On the contrary there is some evidence of stimulation of the immune system following HIFU treatment.

What are the intended benefits of treatment?

If the tumour is small and localized the intention of the treatment is to be curative. If the tumour is very extensive, or in a difficult anatomical region, it may only be possible to reduce the bulk of the tumour. In this case, the intention of treatment is to be palliative, the goals being to increase survival and to improve quality of life.

It has already been mentioned that HIFU treatment can stimulate the immune system In some treated patients, tumours that were not directly targeted have been seen to become smaller, and even disappear. There is also evidence from Europe, where HIFU is being used to treat prostate cancer, of a similar immune response.

To be treatable with HIFU a tumour must be “lumpy” and in a position where it is visible using imaging ultrasound. There must be a clear path for the HIFU through to the tumour. Cancers near the surface of the skin are not treated, owing to the danger of skin damage. A decision on whether or not a tumour is treatable will be made before treatment commences.