Roadmap: helium ion therapy

Abstract

Helium ion beam therapy for the treatment of cancer was one of several developed and studied particle modalities in the 1950’s, leading to clinical trials beginning in 1975 at the Lawrence Berkeley National Laboratory. The trial shutdown was followed by decades of research and clinical silence on the topic while proton and carbon ion therapy made debuts at research facilities and academic hospitals worldwide. The lack of progression in understanding of principle facets of helium ion beam therapy in terms of physics, biological and clinical findings persist today, mainly attributable to its highly limited availability. Despite this major setback, there has been an increasing focus on evaluating and establishing clinical and research programs using helium ion beams, with both therapy and imaging initiatives to supplement the clinical palette of radiotherapy in the treatment of aggressive disease and sensitive clinical cases. Moreover, due its intermediate physical and radio-biological properties between proton and carbon ion beams, helium ions may provide a streamlined economic steppingstone towards an era of widespread use of multi-particle approaches to light and heavy ion therapy. This roadmap presents an overview of the current state-of-the-art and future directions of helium ion therapy: understanding physics and improving modeling, understanding biology and improving modeling, imaging techniques using helium ions and refining and establishing clinical approaches and aims from learned experience with protons. These topics are organized and presented into three main sections, outlining current and future tasks in establishing clinical and research programs using helium ion beams — A. Physics B. Biological and C. Clinical Perspectives.

Radiotherapy with Helium Ions Has the Potential to Improve Both Endocrine and Neurocognitive Outcome in Pediatric Patients with Ependymoma

“…For biological dose optimization, the modified microdosimetric kinetic model (mMKM) was used with the clinical parameters as described before [ 23 ]. All the dose specifications of helium ions are considered as biological doses (GyRBE).…”

Dosimetric response of Gafchromic™ EBT‐XD film to therapeutic protons

“…5 Therefore, LET of the primary ion beam increases along the ion beam path and reaches its maximum at the end of the range. [6][7][8] Studies have reported LET dependence in EBT-2 and EBT-3 films, 9,10 but quantitative analyses of LET dependence in EBT-XD films are scarce. Therefore, the first aim of the current study was to characterize the proton LET dependence of EBT-XD films.…”

Spot‐scanning hadron arc (SHArc) therapy: A proof of concept using single‐ and multi‐ion strategies with helium, carbon, oxygen, and neon ions

“…A recent roadmap discusses the potential role of helium ions in MIT. 53 Additional SHArc optimizations were attempted with various mixtures, for example, He+C; however, such mixtures did not provide ideal MIT conditions like improved D Phys and RBE homogeneity without increasing entrance channel dose contributions in the target volume and therefore,we conclude that this application of SHArc, that is, optimization with a single energy per angle to increase central target LET may not be feasible unless more beam energies are allowed during optimization. These results were anticipated considering prior multi-ion works,which showed difficulty in establishing uniform RBE/physical dose distributions while meeting primary optimization goals of target coverage homogeneity.…”