Heavy ion microbeam radiation therapy for the treatment of radiation resistant cancers

Richard Shaw, Medical Physicist, Herbert-Herman Cancer Center, Sparrow Health System
Tuesday, Sep 01, 11:00 AM - Special Seminar
1200 FRIB Laboratory

Abstract:  The aim of this proposal is to use the NSCL to study the radiobiology of heavy ion, microbeam radiation therapy (HIMRT). In particular, we will study how HIMRT affects normal tissues and radiation resistant cancers. Microbeam radiation therapy (MRT) is an experimental radiation therapy (RT) technique that is showing promise in enhancing outcomes of cancer treatment. MRT uses high-intensity, thin “slits” of radiation, such as photons or protons. The beams are narrow enough to consider how an array of cells responds to very high doses of ionizing radiation, while cells a short distance away experience a substantially reduced dose. In contrast, the response to conventional radiation therapy (CRT) is linked to the homogeneous distribution of radiation over larger volumes. MRT is being investigated as a method to treat cancers that are resistant to CRT. Investigators hypothesize that very small radiation beams can induce microscopic changes that cancerous tissues have more difficulty repairing than normal tissues. When comparing MRT to CRT, investigators are concluding that the viability of normal tissues is significantly higher after MRT treatment and that genetic damage to normal tissue is significantly reduced. They project that this might bolster normal tissue protection during treatment. The largest pre-clinical data is being presented from European Synchrotron Radiation Facility (ESRF) using low-energy, photon-based MRT to irradiate animals. Experiments at ESRF observe favorable results suppressing and ablating tumors, even for very aggressive, radiation resistant tumors. In addition, they demonstrate the ability to control intracranial tumor growth in rodents while sparing normal tissue. Irradiated duck embryos show that normal brain tissue has approximately a 10-fold increase in radiation tolerance for MRT as compared to CRT, which is crucial to maintaining the brain’s function following treatment. Though these results are encouraging, most MRT facilities are hamstrung by their use of low photon energies that have limited penetration and intensity. This reduces their therapeutic capabilities for humans. The use of broad beam heavy ion RT (i.e. carbon ion RT facilities located in Japan, Italy, Germany and China) is ideal for targeted RT, due to its penetration capabilities and sharp Bragg-peak, and has an enhanced radiobiological response due to its high linear energy transfer. By combining heavy ion charge particle therapy with MRT, HIMRT will achieve a superior balance of tumor control versus complications than with either broad beam heavy ion RT or MRT alone.