Association of rurality with brain metastasis at initial diagnosis of lung cancer

Brain metastases from lung cancer are associated with worse prognosis and treatment complexity. While prior studies have described the incidence and outcomes of brain metastases in lung cancer, the association of rural residence with brain metastasis at the time of diagnosis remains unclear. This study evaluated that association while accounting for sociodemographic and access variables.

We performed a retrospective cohort study using the National Cancer Database to identify adults diagnosed with stage I-IV primary lung cancer between 2013 and 2023. The primary outcome was the presence of brain metastases at diagnosis. The primary exposure was patient residence in a rural area (defined as counties that were completely rural or had fewer than 2,500 urban residents). Multivariable logistic regression estimated odds ratios (ORs) with confidence intervals (CIs) for brain metastasis at diagnosis, with a secondary model adjusting for straight line distance to the treating facility.

Among 1,134,457 eligible patients, 12% presented with brain metastases at diagnosis and 2% resided in rural counties. Brain metastases were more common among rural than urban patients (13% vs. 12%). After multivariable adjustment for patient characteristics, rural residence was associated with higher odds of brain metastasis at diagnosis (OR: 1.09, 95% CI: 1.05, 1.13). This association persisted after accounting for distance.

Rural residence was associated with a modestly higher likelihood of brain metastasis at lung cancer diagnosis, independent of distance, suggesting that structural access barriers beyond geographic distance may contribute to differences in diagnostic evaluation, staging completion, or documented brain metastasis at presentation.