Towards Laser Driven Particle Therapy: from in vitro studies to human tumor irradiation on mice

The novel technology of particle acceleration by high intensity lasers promises more compact and cost effective ion sources as well as electron beams of very high energy for radiotherapeutic application. However, compared to conventional beams, laser-driven acceleration results in different beam properties like ultra-short and very intensive pulses, inherent pulse-to-pulse fluctuations, low pulse repetition rate, large beam divergence and broad energy distribution. In consequence, the future medical application of these particle beams requires not only a high power laser system but also new technical solutions for dose delivery and quality assurance as well as comprehensive research on the radiobiological consequences of ultra-short radiation pulses with high pulse dose.
During the last years the laser-driven technology was developed at such a rate that cell samples and small animals can be irradiated. Within the joint research project “onCOOPtics” extensive in vitro dose response studies were already performed comparing the radiobiological effects of laser driven electron and proton beams to their conventional equivalents. As overall result, the obtained dose-effect relationships for human tumor and human normal tissue cells reveal no difference between conventional and laser-driven beams. In a second translational step, in vivo experiments were recently established at the laser system JETI. Although the experiments were motivated by future proton trials, first attempts were performed with laser accelerated electrons, since the homogeneous delivery of prescribed doses to a 3D target volume is easier for electrons than for protons. Tumor irradiation was realized for the murine sarcoma KHT and the human squamous cell carcinoma FaDu grown on nude mice ear. Doses of up to 14 Gy were applied and the radiation induced tumor growth delay was investigated and later on compared to those obtained after similar treatment at a conventional electron Linac. Moreover, the successful performance of such an experiment campaign over a period of several weeks underlines the stability and reproducibility of all implemented methods and setup components. Further experiments with laser accelerated protons are in progress.
The work was supported by the German Federal Ministry of Education and Research
(BMBF), grant nos. 03ZIK445 and 03Z1N511.