Comparison of radiotherapy techniques for breast cancer
15 March 2011
A new study comparing standard imaging and image guided radiotherapy (IGRT) for the treatment of breast cancer has been funded by the EME programme.
Radiotherapy is an effective treatment for breast cancer which kills any remaining cancer cells left after surgery. It can also improve the cure rate for women with early breast cancer. However, for a number of patients the cancer returns and these recurrences happen close to the site of the original cancer (the tumour bed). A boost dose of radiotherapy is delivered to the area to reduce the risk of recurrence.
In order to ensure that the tumour bed is always in the area targeted by the radiotherapy machine, a safety margin is added around the known tumour bed position. This safety margin accounts for daily variations in the breast position, including breathing motion during treatment. At present, checks on treatment accuracy use x-ray imaging and are limited to measurement of the positions of lung and bone due to the inability of the x-rays to see the tumour bed. Since most of these tumour recurrences occur close to the site of the original cancer, and the tumour bed cannot be seen directly, the added safety margin means that a high dose of radiotherapy has to be given to twice as much healthy breast tissue than would be needed if the tumour bed could be seen.
The study (IMPORT-IGRT), led by Professor Philip Evans of The Institute of Cancer Research, will evaluate how effective the IGRT technique is in reducing the volume of tissue treated to a high dose and what are the consequent reductions in risk to normal tissue compared with the standard technique. The study is a collaboration between the ICR, The Royal Marsden NHS Foundation Trust, Addenbrooke’s Hospital NHS Trust, Clatterbridge Centre for Oncology, Ipswich Hospital NHS Trust, Torbay Oncology Unit, Royal Preston Hospital
This builds on the IMPORT-HIGH (Intensity Modulated and Partial Organ Radiotherapy) trial led by Professor John Yarnold of The Institute of Cancer Research and Dr Charlotte Coles of Addenbrookes Hospital, which is using IGRT to enable reduced breast treatment volume. An important innovation in IMPORT is a national agreement with breast cancer surgeons to mark the walls of the surgical excision cavity with small titanium clips that can be imaged during radiotherapy. This will then allow IGRT to be used to image the tumour bed before each treatment. IMPORT-IGRT plans to quantify the size of the effect of this on treatment outcome.
“Our pilot studies suggest that safety margins around the tumour bed can be greatly reduced, leading us to expect a lower rate of long-term complications such as breast shrinkage, hardness, pain and rib fracture” says Professor Evans. “We will measure the accuracy of radiotherapy with IGRT compared with standard imaging. We will also be able to calculate the margin of healthy tissue that would need to have been added around the tumour bed if standard imaging had been used.”
The research team hope to recruit 250 women from the IMPORT trial to participate in this study.
The full project details can be viewed on the project page: http://www.eme.ac.uk/projectfiles/0915016info.pdf