Inequitable access to proton beam therapy in Europe: Efficiency, equity, and strategic infrastructure planning to...

Proton beam therapy (PBT) may reduce treatment-related toxicity, but access remains highly unequal across Europe and may worsen as cancer incidence rises. We aimed to quantify current accessibility, project supply-demand dynamics to 2030, and identify where additional capacity could most reduce spatial inequality.

We analysed PBT accessibility across 31 countries (EU-27, UK, and EFTA; 69,918 subregions) using the enhanced two-step floating catchment area (E2SFCA) method. Projections to 2030 included a baseline scenario incorporating planned facilities and rising cancer incidence, and an equity-optimised scenario assessing one additional single-room PBT unit within each eligible country, with countries ranked by the absolute reduction in the national weighted Gini index.

Estimated demand for PBT in 2025 totalled 78,500 patients. Despite existing infrastructure, over 56,000 patients lived in areas with no access or critical shortages (E2SFCA < 0.25). Projections to 2030 reveal divergent regional trajectories: Southern and Eastern Europe are projected to improve spatial equity through planned expansions, whereas Northern and Western Europe face declining capacity-to-demand ratios. Among the ten countries with the largest absolute modelled reductions in inequality, adding one strategically located single-room PBT facility was projected to reduce the national weighted Gini index by a mean of 35.4 %.

Substantial capacity deficits and spatial inequities persist across the European PBT landscape and are projected to intensify by 2030 without targeted policy intervention. While centralised, high-throughput centres remain efficient in smaller, densely populated countries, they are insufficient to ensure equitable access in geographically extensive nations, where decentralised networks incorporating single-room facilities may be more effective.