Prioritizing radiotherapy infrastructure in depopulating societies: a 2050 blueprint from Akita, Japan.

Clinical Snapshot

Key Findings

• P Value: Not applicable — deterministic spatial modelling study; inferential statistics not used

• Effect Size: Current single IMRT facility: 70.3% coverage (285,273 residents uncovered). Optimised five-facility placement: 99.99% coverage (89 residents uncovered). Under 2050 projections, three optimised facilities maintain >99% coverage.

• Primary Outcome: 60-minute automobile travel-time coverage for IMRT-capable facilities in Akita Prefecture

• Nnt Or Sensitivity: Mean travel time reduced from 42.5 minutes (current single IMRT facility) to 14.2 minutes (optimised five-facility scenario); three temporally stable core locations identified across all projection horizons (2020–2050)

• Confidence Interval: Not reported — deterministic optimisation model; no probabilistic uncertainty bounds provided

Clinical Application

The optimisation methodology is computationally accessible using open-source tools (OSRM, OpenStreetMap) and publicly available population data, making replication feasible for health planners in other regions. However, actual facility establishment requires substantial capital investment, workforce recruitment, and regulatory approval — none of which are modelled. The identification of three stable core locations provides a practical starting point for long-term infrastructure planning. Australia faces analogous challenges in rural and remote radiotherapy access, with geographic inequity in cancer treatment well-documented by the Australian Institute of Health and Welfare. The p-median methodology used in this study could be directly applied to Australian states with dispersed, ageing populations (e.g., Western Australia, Queensland, South Australia). IMRT is funded under Medicare Benefits Schedule (MBS) item numbers for eligible indications, and the TGA regulates linear accelerator equipment. The RACGP and Cancer Australia have both identified geographic access to cancer care as a priority equity issue. Australian health planners could adapt this framework using ABS mesh population data and PSMA road network data. The 60-minute threshold used in this study aligns broadly with Australian rural health access benchmarks, though Australian distances are typically far greater, suggesting a longer threshold may be more appropriate in the Australian context. State-based cancer plans (e.g., NSW Cancer Plan, Victorian Cancer Plan) could incorporate this modelling approach for IMRT infrastructure prioritisation. Residents of super-aged, depopulating regions requiring access to IMRT for cancer treatment; most directly applicable to Akita Prefecture, Japan, and analogous demographically declining prefectures. Methodology is transferable to any jurisdiction with comparable population mesh data and road network information.

Abstract

In super-aged and depopulating societies, repeated travel requirements for radiotherapy (RT) can amplify geographic inequities in access to advanced techniques. The aim of this study was to determine optimal placement of intensity-modulated radiotherapy (IMRT)-capable facilities in Akita Prefecture-a leading-edge case of Japan's demographic transition-using p-median optimization under population projections through 2050. Using 1-km mesh population data for 2020 and official projections for 2030, 2040 and 2050, we calculated one-way automobile travel times from each mesh centroid to RT facilities with the Open Source Routing Machine based on OpenStreetMap road data. A 60-min travel-time threshold defined access coverage. IMRT-capable facilities were identified from official insurance-designation lists. Optimal placement was determined using a population-weighted p-median model, with the number of facilities prespecified as one per 200 000 population. In 2020, 10 external-beam RT facilities provided near-universal 60-min coverage (99.99%; mean 12.8 min), whereas the single IMRT-capable facility covered only 70.3% (uncovered 285 273; mean 42.5 min). Optimized placement with five IMRT-capable facilities increased coverage to 99.99% (uncovered 89) and reduced mean travel time to 14.2 min. Under population projections, optimized placement maintained >99% coverage through 2050 with three facilities, and three core locations were consistently selected across all time horizons. These temporally stable core locations can serve as priority targets for long-term IMRT infrastructure investment in aging and depopulating regions.

References

1. 1.Koike, Y., Nakamura, S., & Wada, Y. (2026). Prioritizing radiotherapy infrastructure in depopulating societies: a 2050 blueprint from Akita, Japan. Journal of Radiation Research. https://doi.org/10.1016/j.ijrobp.2025.08.041