Disparities in Access to Radiation Oncology Facilities Among American Indian/Alaska Natives and Hispanics in Metro and Non-Metro Washington State

Abstract

Racial and ethnic minorities in Washington State (WA) experience higher cancer mortality relative to whites. We sought to characterize differences in travel distance as a marker for access to radiation therapy (RT) facilities in WA and one possible contributing factor to cancer disparities.Geocoded mortality data from the WA Department of Health (2011-2018) were used to identify decedents with mortality related to all causes, all cancers, and cancers likely requiring access to RT (defined as estimated RT usage rate > 50% by anatomical subsite corresponding to ICD-9 or 10 code). Race was defined per US Office of Management and Budget 1997 standard and ethnicity as Hispanic or non-Hispanic. RT facility locations were identified from the Directory of Radiotherapy Centers and validated by internet search or phone calls. Road network distance from decedent's residence to nearest RT facility was calculated on a geographic information platform. Generalized mixed models were used for statistical analysis.We identified 109,134 cancer-related deaths of which 60,973 likely required RT. Among decedents with cancers likely requiring RT, non-Hispanic (NH) American Indian/Alaskan Native (AI/AN) decedents would have had to travel 1.16 times (95% CI 1.09-1.24) farther to reach the nearest treatment facility compared to NH whites. This association existed in metro counties but was more pronounced in non-metro and rural counties, where NH AI/ANs would have had to travel 1.39 times farther compared to NH whites (95% CI 1.22 - 1.58). This translated to an average of 83 miles (SD = 22) for NH AI/AN in rural areas to travel to RT centers whereas NH Whites in rural areas would have had to travel on average 59 miles (SD = 28). Hispanics would have had to travel 1.11 times farther to reach the nearest facility compared to NH whites (95% CI 1.06 - 1.16), primarily due to differences in urban areas. NH African American, NH Asian, and NH Native Hawaiian decedents lived closer to RT facilities compared to the NH white decedents. Based on our findings, we estimated that expanding the federal "safe harbor" restrictions on health systems providing transportation from 50 to 75 miles could open up needed services for 96% of rural NH AI/ANs.NH AI/ANs and rural decedents experience stark disparities in access to RT facilities in WA state. The findings call for creative initiatives to improve access to critical cancer treatment services to combat racial, ethnic and rural disparities in cancer deaths. In depth analysis of local barriers to access for minority communities is necessary to devising practical solutions such as advocating for policy change for "safe harbor" restrictions.