Tracking down the links between charged particles and biological response: A UK perspective.

The UK has a long history of radiobiology research into charged particles, with interest likely to expand in the coming years following the recent government announcement of £250 million to build two proton beam therapy facilities in the UK. A brief overview of research and facilities past and present with respect to radiation protection and oncology along with biological consequences and underlying mechanisms will be presented and discussed. Increased knowledge of the mechanisms underpinning the radiation action on biological systems is important in understanding, not only the risks associated with exposure, but also in optimising radiotherapy treatment of cancer. Ionizing radiation is always in the form of structure tracks which are a unique characteristic of ionizing radiation alone producing damage grossly different and far more biologically effective than endogenous damage. The track structure is the prime determinant of biological response to DNA, with charged particles of increasing LET leading to an increase in the frequency and complexity of clustered DNA damage. High-LET particles will also produce non-homogeneous dose distribution through a cell nucleus resulting in correlated DNA breaks along the path of the particle and an increase in the probability of complex chromosomal rearrangements. However it is now well established that there is variety of phenomena that do not conform to the conventional paradigm of targeted radiobiology, but there is insufficient evidence to assess the implications of these non-targeted effects for radiotherapy or relevance to risk for human health. [ABSTRACT FROM AUTHOR]