Residence in Rural Areas of the United States and Lung Cancer Mortality. Disease Incidence, Treatment Disparities, and Stage-Specific Survival.

RATIONALE: There is increased lung cancer mortality in rural areas of the United States. However, it remains unclear to what extent rural-urban differences in disease incidence, stage at diagnosis, or treatment explain this finding.
OBJECTIVES: To explore the relationship between smoking rates, lung cancer incidence, and lung cancer mortality in populations across the rural-urban continuum and to determine whether survival is decreased in rural patients diagnosed with lung cancer and whether this is associated with rural-urban differences in stage at diagnosis or the treatment received.
METHODS: We conducted a retrospective cohort study of 348,002 patients diagnosed with lung cancer between 2000 and 2006. Data from metropolitan, urban, suburban, and rural areas in the United States were obtained from the Surveillance, Epidemiology, and End Results program database. County-level population estimates for 2003 were obtained from the U.S. Census Bureau, and corresponding estimates of smoking prevalence were obtained from published literature. The exposure was rurality, defined by the rural-urban continuum code area linked to each cohort participant by county of residence. Outcomes included lung cancer incidence, mortality, diagnostic stage, and treatment received.
MEASUREMENTS AND MAIN RESULTS: Lung cancer mortality increased with rurality in a dose-dependent fashion across the rural-urban continuum. The most rural areas had almost twice the smoking prevalence and lung cancer incidence of the largest metropolitan areas. Rural patients diagnosed with stage I non-small cell lung cancer underwent fewer surgeries (69% vs. 75%; P < 0.001) and had significantly reduced median survival (40 vs. 52 mo; P = 0.0006) compared with the most urban patients. Stage at diagnosis was similar across the rural-urban continuum, as was median survival for patients with stages II-IV lung cancer.
CONCLUSIONS: Higher rural smoking rates drive increased disease incidence and per capita lung cancer mortality in rural areas of the United States. There were no rural-urban discrepancies in diagnostic stage, suggesting similar access to diagnostic services. Rural patients diagnosed with stage I non-small cell lung cancer had shorter survival, which may reflect disparities in access to surgical care. No survival difference for patients with advanced-stage lung cancer is attributed to lack of effective treatment during the time period of this study.