Apr 4, 2007
Where physics meets surgery
Radiation therapy is traditionally a drawn-out affair during which patients are irradiated in small fractions over a period of several weeks. This is inconvenient for patients as well as for overstretched clinical teams. Intraoperative radiation therapy (IORT), the intensive irradiation of a tumour or tumour bed while it is exposed during surgery, is one streamlined alternative being looked at by more and more oncology teams.
In principle, for some treatment sites, IORT could replace adjuvant external-beam radiotherapy with a single radiation dose delivered during surgical tumour removal. Alternatively the technique can be used as a boost dose to shorten postoperative treatment cycles. Despite its undoubted potential, however, the use of IORT is restricted by the limitations of existing equipment and facilities.
A team from Ninewells Hospital (Dundee, Scotland) reported on its clinical experience with IORT - specifically the Intrabeam system from German equipment maker Carl Zeiss - at the UK Radiation Oncology (UKRO) conference in Edinburgh last month. Rather than a large linac, IORT uses a portable X-ray source that's "small enough to fit into the palm of your hand", according to Kris Armoogum, a physicist involved in testing the Intrabeam system at Ninewells.
After the surgeon cuts out a tumour, the source is fitted with a spherical applicator the right size to fit into the tumour bed. The applicator is positioned in the wound and a high dose of radiation administered while the patient is still anaesthetized. After this process is complete, the wound is sewn up and the patient is free to go.
"There are plenty of advantages for the patient, who can come in and have a lumpectomy and their radiation treatment in one day in hospital and go home... as opposed to having to come in for external-beam therapy for the next five weeks," explained Philip Peacock, Carl Zeiss area manager for surgical products. He added that this represents a big financial saving for many patients and their families, as well as for the government.
At the moment, IORT is being used to treat breast and neurological tumours. "Some patients from the early days have had their five-year follow-up and their results have been very positive; certainly as good - if not slightly better - than with external-beam therapy," claimed Peacock. The experience at Ninewells Hospital backs this up, but Armoogum also emphasized several practical issues associated with IORT applications.
Because IORT is administered during the surgical procedure it requires a diverse team of surgeons, physicists, nurses, oncologists and anaesthesiologists to work together. Armoogum stressed the need for a dedicated IORT coordinator to ensure that everyone ends up in the right place at the right time. Irradiating patients during surgery also adds significantly to the time they spend under general anaesthetic. This means that unless theatre efficiency improves, IORT will not be suitable for many elderly or weak patients.
The procedure is also quite intensive for the physicists involved. They can only set up the IORT system, calculate the irradiation time and take care of radiological protection for the patient and surgical team once the tumour has been removed and the wound measured. At least two physicists are required, and they have to work fast. Armoogum anticipates that this could lead to workflow problems, and that more physicists will be needed if IORT is adopted on a large scale.
Carl Zeiss is currently modifying the Intrabeam system to treat tumours in other locations. Peacock told medicalphysicsweb: "It has potential for other cancers, but there are issues with the shape of the applicator, and positioning, that haven't been resolved yet. Colorectal is an area that's being looked at."
Armoogum is also optimistic about the prospects for IORT: "Through reliance on an oncology nurse to coordinate the programme we have successfully set up an IORT service. Our experience could serve as a model for introducing IORT into other centres."
About the author
Michelle Jeandron is science and technology reporter on medicalphysicsweb.