Cyberknife treatment for prostate cancer

Cyberknife is an exciting new tool for the eradication of benign and malignant tumours (cancers that are localised in one place). With other radiotherapy techniques the dose is limited by the damage that could be done to the surrounding normal tissue if higher dosage was delivered. Cyberknife uses the same type of radiation that is used in conventional radiotherapy, but whereas conventional radiotherapy encompasses some normal adjacent normal tissue in the high dose zone (and spares this tissue from damage by treating in lots of small dose fractions/treatments), Cyberknife can safely place a huge dose of radiation on the target whilst sparing the surrounding normal body tissues by virtue of a very steep dose gradient at the margin of the targeted prostate gland. Cyberknife can even give a focal boost within the gland (e.g. if only the right lobe and mid gland region was biopsy positive). Such a high dose of radiation delivered to the tumour can destroy it as effectively as removal by a surgical operation. It may be marginally superior to IMRT for certain tumours and gives treatment over only one week.

The technique employs a device called a Linear Accelerator (Linac) that generates a beam of radiation. This is mounted on a robotic arm which can manoeuvre the Linac to direct its ‘pencil’ beam from any angle with a high degree of accuracy, utilising sophisticated computer control. The tumour is scanned and every point in the tumour is located precisely by three dimensional co-ordinates which are stored in the computer (this is called Stereotactic Mapping). The patient lies on the therapy couch/table in the treatment room and the on-table imaging facility allows the tumour to be localised (located by the hardware). After the target tumour has been localised, the robotic arm automatically lines up the Linac to deliver beams of radiation from many different directions. The direction of the beam is controlled by advanced planning software so that the tumour is slowly obliterated by a radiation dose that is built up over a period of time from one to several hours.

Many cancers may be effectively treated by Cyberknife, which forms a non-invasive alternative to many surgical options, without the inherent risks that are always present with surgical procedures. Cancers and tumours in the head, brain, spine, lung, liver, pancreas, prostate and sarcomas may all respond well to this new technique. The Cyberknife can also treat metastases, where the primary cancer has spread to other parts of the body.