Residents in American Indian/Alaska Native (AI/AN)-majority and rural census tracts must travel greater distances to reach lung cancer screening (LCS) facilities, according to a study published in Annals of Internal Medicine.¹

The researchers noted that early-stage lung cancer diagnosis improves prognosis as patients with localized lung cancer have higher 5-year survival rates than those with metastasized lung cancer (60% vs 6%).² Therefore, in 2021, the US Preventive Services Task Force (USPSTF) recommended annual LCS for those aged between 50 and 80 who have a 20-year history of smoking 1 pack per day and either currently smoke or have quit within the past 15 years.³

However, the density of LCS facilities is not uniform nationwide.¹ Past research found that 15% of the US population and 48% of the rural population aged 55 to 79 did not live within 30 miles of an LCS facility.⁴ Also, the average distance to the nearest LCS facility was 44 miles for 454 of the 594 federally recognized AI/AN tribes, with 140 tribes located more than 200 miles from a facility.⁵

Because of its potential role in screening uptake, the researchers examined differences in LCS facility access by race, ethnicity, and rurality.¹

Some populations face significant disparities in accessing lung cancer screening facilities, with American Indian/Alaska Native (AI/AN)-majority and rural census tracts facing the greatest travel distances. | Image Credit: Nattakorn – stock.adobe.com

The study was conducted at the census tract level. Consisting of 2500 to 8000 people, census tracts are relatively permanent geographic units roughly equivalent to neighborhoods used to tabulate and present data from the census.

The outcome variable was road network distance in miles between a census tract and the nearest LCS facility. The researchers represented census tracts by the latitude and longitude of population-weighted centroids. Similarly, LCS facilities were represented by the latitude and longitude of their geocoded address. Curated by the American College of Radiology, the LCS Registry provided the names and addresses of facilities offering LCS as of January 2021 using low-dose computed tomography; all facilities associated with the American College of Radiology were included.

The independent variables were census tract rurality and racial and ethnic composition. The researchers used the 2019 Community Survey 5-year data to create a categorical indicator of each census tract’s predominant racial and ethnic identities. They chose people aged 45 to 84 based on the USPSTF annual LCS guidelines and the availability of US census data by race and ethnicity. The researchers classified census tracts as majority (>50%) AI/AN, Asian, Black, NHW, no single race, or Hispanic.

Census tract rurality was defined with rural-urban commuting area (RUCA) codes. The researchers considered primary codes 1 to 3 as metropolitan, 4 to 6 as micropolitan, and 7 to 10 as small town/rural.

They explained that census tract characteristics were summarized by medians with IQRs or by frequencies with percentages. In particular, the distance variable was log-transformed to account for skewness. Additionally, the researchers used ordinary least-squares regression models to examine the associations between the distance to the nearest LCS facility and each census tract’s rurality, race, and ethnicity.

The study sample included 71,691 (98.5%) of the 72,757 US census tracts. Of these, AI/AN-majority census tracts accounted for 0.2%; among the AI/AN-majority tracts, 77.4% were in micropolitan or small town/rural areas. Consequently, based on the researchers’ defined racial and ethnic categories, the AI/AN population had the smallest census tract representation.

Overall, the geometric mean (GMR) distance to the nearest LCS facility was 6.5 miles. However, mean distances to the nearest LCS facility were generally much larger in more rural tracts. Compared with 4.4 to 6.9 miles in other majority census tracts, AI/AN-majority tracts had the longest GMR distance to the nearest LCS facility at 49.6 miles. Therefore, AI/AN majority and small town/rural census tracts indicated a trend toward greater GMR distances to the nearest LCS facility than other race- and ethnicity-majority and metropolitan census tracts.

The researchers determined that distances to the nearest LCS facility in AI/AN-majority census tracts were 5.26 times (426%; 95% CI, 4.62-5.99) farther than those in NHW-majority tracts. Conversely, distances to the nearest LCS facility in Asian-, Black-, and Hispanic-majority tracts were 16% (GMR, 0.84; 95% CI, 0.79-0.90), 39% (GMR, 0.61; 95% CI, 0.59-0.63), and 7% (GMR, 0.93; 95% CI, 0.90-0.95) shorter, respectively, than those in NHW-majority tracts.

Adjusting for RUCA categories reduced the mean distance in AI/AN-majority census tracts, but it was still 3.16 times the distance in NHW-majority tracts. It also reduced the observed advantage among Asian- (GMR, 0.90; 95% CI, 0.85-0.95) and Black-majority (GMR, 0.79; 95% CI, 0.76-0.80) census tracts. Additionally, adjusting for RUCA categories changed the GMRs from slightly closer to farther away for Hispanic-majority tracts (GMR, 1.09; 95% CI, 1.07-1.12).

Lastly, the researchers acknowledged their study’s limitations, including the common misclassification of the AI/AN race in census and vital statistics data; this impedes the planning, implementation, and evaluation of public health strategies to address health disparities within this population. Despite their limitations, they used their findings to encourage future actions and research.

“This study offers insights into the placement of future imaging locations and use of mobile LCS units to ensure that all populations have equitable access to LCS services,” the authors concluded. “Future research documenting the extent to which equitable access to LCS facilities affects LCS uptake and lung cancer outcomes would be an important contribution to achieving cancer health care equity.”

References

1. Amiri S, Wilshire CL, Muller CJ, et al. Census tract rurality, predominant race and ethnicity, and distance to lung cancer screening facilities. Ann Int Med. doi:10.7326/M24-0124
2. Cancer stat facts: lung and bronchus cancer. National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) Program. Accessed January 9, 2025. https://seer.cancer.gov/statfacts/html/lungb.html
3. US Preventive Services Task Force, Krist AH, Davidson KW, et al. Screening for Lung Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;325(10):962-970. doi:10.1001/jama.2021.1117
4. Eberth JM, Bozorgi P, Lebrón LM, et al. Geographic availability of low-dose computed tomography for lung cancer screening in the United States, 2017. Prev Chronic Dis. 2018;15:E119. doi:10.5888/pcd15.180241
5. Peña MA, Sudarshan A, Muns CM, et al. Analysis of geographic accessibility of breast, lung, and colorectal cancer screening centers among American Indian and Alaskan Native tribes. J Am Coll Radiol. 2023;20(7):642-651. doi:10.1016/j.jacr.2023.04.007