Optimal use of light ions for radiation therapy

The light ions have a unique role in the development of modern radiation therapy where Biological Optimized Radiation Quality and Intensity Modulated Radiation Therapy (QMRT and IMRT) are increasingly coming to clinical use, not least through a systems biology approach to therapy optimization. The traditional dose distributional qualities of light ions like penumbra and depth dose are ideally suited for high quality radiation therapy, and their radiation biological properties are also ideal for eradicating large complex generally hypoxic tumor volumes with minimal damage to surrounding normal tissues. The remaining challenge to a more wide spread clinical use of light ions are to improve the sensitivity and specificity of Molecular Tumor Imaging to more accurately localize the tumor tissues and to develop fast scanning systems that preserve the fundamental biological and physical advantages of the light ions. For optimal application it is essential to modulate the ion beams and select the best possible ion species depending on the molecular and anatomic properties of the tumor and that is where systems biology will play a key role. For small hypoxic tumors the high apoptotic induction at the Bragg peak of lithium ions is ideal whereas large tumor masses may require carbon and oxygen ions and microscopically invasive tumors may be best treated by photons, electrons, protons and helium ions. (author)