Using Geospatial Analysis to Evaluate Access to Lung Cancer Screening in the United States

Abstract

BACKGROUND: Screening current and former heavy smokers 55 to 80 years of age for lung cancer (LC) with low-dose chest CT scanning has been recommended by the United States Preventive Services Task Force since 2013. Although the number of screening facilities in the United States has increased, screening uptake has been slow. RESEARCH QUESTION: To what extent is geographic access to screening facilities a barrier for screening uptake nationally? STUDY DESIGN AND METHODS: Screening facilities were defined as American College of Radiology (ACR) Lung Cancer Screening Registry (LCSR) facilities. Analysis was performed at different geographic levels using a road network to calculate travel distances for the recommended age groups. Full access to screening was defined as the entire 55-to 79-year-old population being within 40 miles of an ACR LCSR facility. No access was defined as lack of access by the entire target population. Partial access was expressed in intervening quartiles. A geospatial approach then was used to integrate accessibility with smoking prevalence and LC mortality rates to identify potential focus areas visually. RESULTS: Screening facilities addresses were geocoded to identify 3,592 unique locations. Analysis of census tracts and aggregation to counties revealed that among 3,142 counties, adults 55 to 79 years of age have full access to an LC screening registry facility in 1,988 (63%) counties, partial access in 587 (19%) counties, and no access in 567 (18%) counties. Overall, less than 6% of those 55 to 79 years of age do not have access to registry screening facilities. Variation in screening facility access was noted across the United States, between states, and within some states. INTERPRETATION: It is recommended to calculate accessibility using subcounty geographies and to examine variation regionally and within states. A foundation geographic accessibility layer can be integrated with other variables to identify geographic disparities in access to screening and to focus on areas for interventions. Identifying areas of greatest need can inform state and local officials and healthcare organizations when planning and implementing LC screening programs.

Geographic access to lung cancer screening among eligible adults living in rural and urban environments in the United States

“…As expected, Figure 2 shows more people have access as the distance to facilities increases, with almost 70% access at 10 miles to more than 99% access at 100 miles. In agreement with the previous report, 12 approximately 5% of the population does not have access at 40 miles. Overall, 5.1% of the eligible population does not reside within 40 miles of a facility, and this proportion is markedly higher among individuals living in micropolitan and rural counties at 17.1% and 24.5%, respectively.…”

“…Geospatial analysis is often used to calculate proximity, assess the availability of health services, identify gaps in resources, and inform public health policies. 12,15,16 We used Esri's ArcGIS 10.6.1 (esri.com) for mapping and spatial analysis. Maps throughout this article were created using ArcGIS software by Esri.…”

“…On the basis of a recent evaluation of methodologies for estimating access, 12 we used road network analysis (preferred over the Euclidean distance method [16][17][18] ) to calculate distances between population centers (represented by census tract centroids) and facilities. Population estimates for the 50-to 80-year age group were downloaded from the US Census (2013-2018 American Community Survey 5-year estimates).…”

If We Build It, They Will Come…Maybe

“…It also should be obvious that a favorable ratio of supply and demand can change; if unnoticed, shrinking demand in the presence of declining access will adversely affect disease control efforts. Sahar et al 9 found that nationwide, <6% of people 55 to 79 years old in the United States did not have access to low-dose CT screening based on 40-mile road distance and identified local disparities. Eberth et al 10 reported an average of 14.9% across all states of people 55 to 79 years old who did not have access within 30-mile Euclidean distance and indicated disparity in distribution of facilities across rural-urban areas.…”

“…Although visual interpretation can be very informative for policy-makers and a catalyst for action, future analyses can benefit from using quantitative spatial analysis at a more granular geographic level and integrating datasets such as mortality and incidence rates to further identify local gaps in services and refine measures of "need." 9 The VHA is a unique national health system that can coordinate services that include quality lung cancer screening across regions. Not only do the results depicted in this article provide valuable information that can assist in program planning and resource allocation, but they also can provide insight into disparities, barriers, and practices that contribute to low lung cancer screening uptake so that these factors can be addressed and overcome.…”