Intraoperative delivery of cell-killing boost radiation - a review of current and future methods

Techniques for intraoperative radiation therapy (IORT), the applications of tumor bed radiation immediately after surgery or utilising intracavitary access, have evolved in recent years. They are designed to substitute or complement conventional external beam radiation therapy in selected patients. IORT has become an excellent treatment option because of good long-term therapy outcomes. The combination of IORT with external beam radiation therapy has the potential to improve local control. The purpose of this paper is to present IORT techniques using gamma and electronic sources, as well as more conventional nuclide-based approaches and to evaluate their effectiveness. Common techniques for radiation of tumor cavities are listed and compared. Radionuclide IORT methods are represented by balloon and hybrid multi-catheter devices in combination with appropriate afterloaders. Electron beam therapy dedicated for use as intraoperative radiation system is reviewed and miniature x-ray sources in electronic radiation therapy are presented. These systems could further simplify IORT, because they are easy to use and require no shielding due to their relatively low photon energies. In combination with additional imaging techniques (MRI, US, CT and NucMed) the application of these miniature x-ray sources or catheter-based nuclide therapies could be the future of IORT.