GIS-Based Spatial Accessibility Analysis of Radiation Therapy Center in Eastern Visayas, Philippines

Radiation therapy centers are vital for effective cancer care, yet in the Philippines, their distribution is uneven, with most facilities concentrated in urban areas. This disparity highlights the need for assessing accessibility to inform the allocation and development of new centers, especially in Eastern Visayas. Geographic Information Systems (GIS) offer a valuable framework for this analysis. In this study, land travel data were collected using the Google Directions API from Google Cloud Services. A multimodal transport model was developed to estimate the weighted travel time (WETT) from various municipalities to the nearest facilities. Spatial accessibility was assessed using the spatial accessibility index (SPAI) calculated through the Modified Huff Three-Step Floating Catchment Area method, which incorporates data on satellite-derived nighttime lights and cancer incidence from Philippine Health Statistics. The results reveal a maximum WETT of 14 hours and 21 minutes between Las Navas, Northern Samar, and the Philippine Oncology Center in Quezon City. Las Navas also has the lowest SPAI value of 1.390, indicating that high WETT correlates with low accessibility. Establishing new radiotherapy centers in Northern Samar could significantly improve access to treatment for residents.