Pancreatic Cancer

CyberKnife stereotactic radiotherapy and its side effects

CyberKnife treatment is a form of highly focused radiotherapy (see ‘Radiotherapy and chemoradiotherapy’) also known as stereotactic radiotherapy or radiosurgery. Unlike conventional radiation therapy techniques traditionally used to treat pancreatic cancer, the CyberKnife machine delivers a high dose of radiation in a single or small number of treatments.
 
The CyberKnife robotic radiotherapy machine is mounted on a highly manoeuvrable base which is controlled by a state of the art guidance system. During the CyberKnife procedure, cameras monitor any patient movement, including breathing, so that the robot can reposition the beam in order to minimise damage to healthy tissue. The area liable to be damaged by this type of radiotherapy is smaller than that liable to be damaged by traditional radiotherapy, but because a high dose of radiotherapy is given in a relatively small number of treatments, the damage itself can be quite severe. For example, CyberKnife treatment can cause severe ulceration and bleeding, a serious complication, but to a small area of the bowel. CyberKnife treatment requires no anaesthesia and patients can usually be treated and go home on the same day.
Although there are potential advantages in using this treatment, most of the published research has been done observing what has happened to people treated with it, rather than comparing it with standard treatments. Without controlled clinical trials it isn’t possible to tell whether a new treatment is any better than an existing one (see ‘Clinical trials’). Because there has been very little testing, doctors know less than they’d like about the side effects of this treatment or how well it works for people with pancreatic cancer. The National Institute of Health and Clinical Excellence (NICE), which advises the NHS on which treatments represent value for money, is assessing the potential benefits of CyberKnife. CyberKnife machines are currently only available in a few NHS hospitals and private clinics and may not be available outside of a clinical trial. 
 
Two men we interviewed had had CyberKnife treatment at a private clinic in London. Michael had had a Whipple’s operation followed by chemoradiotherapy, but in March 2010 he had a recurrence. He was delighted when a multidisciplinary team at a private clinic decided that he was suitable for CyberKnife treatment. Another man, Peter (Interview 43), had inoperable pancreatic cancer. He had some chemotherapy and then heard about CyberKnife treatment. He asked his consultant to refer him to a doctor in a private clinic that provided this treatment.
Before CyberKnife treatment starts people have CT scans. They may also have an MRI scan or Positron Emission Tomography (PET) scan (see ‘Other diagnostic investigations’). A PET scan can show how body tissues are working, as well as what they look like. The doctor puts information from the scans into the CyberKnife machine’s computer. By mapping a tumour three dimensionally before treatment, doctors can calculate the dose of radiation to match the shape, density and position of a tumour. The tumour is then ‘marked’ with tiny particles of gold to define the position of the tumour with millimetre precision. The marker is called a fiducial.
People return to the clinic on another day for the treatment itself. The patient lies inside a plastic mould made to the shape of their body to restrict their movement. This is placed on a movable treatment table and the robotic arm moves around them. During treatment they have to lie very still. The treatment does not hurt. Patients usually have one to five treatment sessions, which can be on consecutive days. Each session generally lasts from 30 to 90 minutes depending on the dosage and the complexity of the tumour, and the treatment duration is considerably more than standard chemoradiotherapy.
The side effects of CyberKnife treatment are similar to the side effects people experience after standard radiotherapy. Although the treatment is convenient as it is given over a small number of treatments (1-5 treatments, compared to 25-30 treatments for standard radiotherapy) but the risk of bleeding and bowel ulceration is higher than standard radiotherapy or chemoradiotherapy. (see ‘Side effects of radiotherapy and chemoradiotherapy’). Michael had some quite bad side effects but Peter had none.
Last reviewed June 2015.
Last updated June 2015.

 

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