Editorial: upright, gantry-less treatments for particle therapy: a potential paradigm shift

Particle therapy can offer physical and biological advantages over conventional photon radiotherapy, yet its widespread adoption remains limited by the cost, scale, and complexity of the accelerators and rotating gantries involved. Upright patient positioning with fixed-beam delivery has re-emerged as a potential alternative that may simplify particle therapy systems. Here we consider upright, gantry-less particle therapy through the lens of philosopher Thomas Kuhn's five criteria for scientific change: (1) simplicity, (2) scope, (3) fruitfulness, (4) consistency, and (5) accuracy. Eliminating rotating gantries stands to improve simplicity by reducing mechanical complexity, weight, and maintenance requirements. This in turn should enable more robust and modular treatment rooms. Early studies also suggest that upright positioning has broad scope: it can reproduce most beam geometries achieved using gantries and appears feasible across multiple anatomical sites. Upright treatments may be fruitful in terms of reducing capital, construction, and operational costs. They will also bring opportunities for technological innovation and potentially for improved patient throughput due to faster ingress and egress. Regarding consistency, upright treatment postures more closely match normal, everyday physiology and are often associated with greater comfort for certain patient groups. Finally, in terms of accuracy, preliminary studies suggest suitable setup reproducibility and comparable treatment planning quality. Upright particle therapy therefore represents a promising alternative delivery model. Further treatment-planning studies, health-economic analyses, and prospective clinical trials are warranted to determine the role of upright systems alongside or in place of gantry-based systems.