Modern medicine relies on advanced radiation-based techniques for cancer treatment, dependent on the parallel fundamental development of condensed-matter and atomic and molecular physics. Representative examples of these include the radiotherapy using ion beams or hadrontherapy, recently introduced in Spain (featuring unprecedented dose-delivery precision and cancer cell-killing ability, minimising damage to healthy surrounding tissues), and targeted radionuclide therapy (in which antibodies or other cancer-cell targeting molecules are linked to alpha-, beta- or Auger-emitting radionuclides, whose emitted radiations of different penetration range are suitable for treating either extended tumours or small cell-scale metastases).

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A Common Mechanistic Feature and Necessary Research

A common mechanistic feature of such techniques is the production and propagation of numerous low-energy electrons, presenting a large cell-killing ability. The latter feature cannot be understood by studying energy deposition at the macroscale, but it is due to the complex patterns of damaging events that low-energy electrons are capable to induce in the volumes with dimensions similar to the sensitive DNA molecules, i.e., at the nanometre scale. Research in condensed matter and atomic and molecular physics is necessary to get a better understanding of the fundamental physical processes underlying the induction of complex biomolecular lesions by inelastic collisions.

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Optimisation and Challenges

Nonetheless, current radiation transport simulation codes lack accurate enough probability distributions for the interaction of low-energy electrons with biological materials different from liquid water, which hinders the modelling. In this project, complementary semiempirical and theoretical models and Monte Carlo simulation methods will be appropriately combined, in order to achieve more detailed and accurate simulations of the interaction of charged particles, particularly low-energy (< 100 eV) electrons, with condensed-phase biomaterials beyond the liquid water approximation (i.e., DNA and other relevant biomolecules such as proteins, lipids, etc. contained in living cell environments). Results from time-dependent density functional theory calculations will be used within the dielectric formalism, which will be further corrected by means of semiempirical low-energy corrections, in order to provide accurate interaction probabilities for low-energy electrons with these materials. The implementation of the new set of energy-loss data in Monte Carlo radiation transport codes, both for ion and electron beams, will produce more detailed simulations of the swift charged particles track-structure in complex biological targets, in order to assess the clustering of damaging events in nanometric targets.

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Potential Impact on Hadrontherapy and Targeted Radionuclide Therapy

These improvements in the modelling might lead to a better understanding of the physical mechanisms behind hadrontherapy and targeted radionuclide therapy and, eventually, to a further optimisation of such advanced medical treatments.