Background: In 2019, the Philippines enacted the National Integrated Cancer Control Act (NICCA) to decentralise cancer care. However, implementation remains limited by a lack of data to guide effective resource allocation. This study provides high-resolution, quantitative baseline data of radiotherapy (RT) accessibility in Luzon, the country’s largest island group, to identify priority areas for infrastructure development.

Methods: A cross-sectional geospatial analysis for 698 municipalities was conducted using the Enhanced Two-Step Floating Catchment Area (E2SFCA) model, integrating provider capacity, population demand and calibrated travel time. Access was modelled under two scenarios: one including all 43 RT facilities and another restricted to the 12 public centres. To quantify financial toxicity, we developed a novel metric, the travel-cost-to-wage ratio. We performed spatial autocorrelation and multivariable regression analyses to identify geographic clusters and key determinants of access.

Results: Profound inequities in RT access were identified. Considering all facilities, 240 municipalities (34.4%) home to 7.5 million people, had no potential access within a 120-minute catchment. The public-only scenario revealed a near-total system inadequacy, with 12.2 million people lacking access. Spatial analysis confirmed a stark core-periphery pattern, with a well-served core centred around the national capital and along the primary north-south expressway network, contrasted with vast, statistically significant ‘RT deserts’ in outlying regions. For 4.9 million people, a single round-trip to the nearest public facility costs more than a day’s minimum wage; this travel-cost-to-wage ratio was the strongest predictor of access (odds ratio = 0.83, p < 0.001).

Conclusion: Spatial access to RT in Luzon is profoundly inequitable, characterised by a stark core-periphery pattern and an inadequate public system that leaves millions reliant on private care or entirely without access. This study provides a data-driven roadmap to guide the strategic implementation of NICCA, ensuring that future resource allocation targets the identified RT deserts to address these critical gaps in cancer care.