Prognostic significance of sites of extrathoracic metastasis in patients with non-small cell lung cancer

Background: Metastatic non-small cell lung cancer (NSCLC) continues to have a poor prognosis despite recent advances in both targeted radiotherapy methodologies such as stereotactic body radiotherapy (SBRT) and immunotherapies. The impact of location of metastatic disease in patients with NSCLC has not been investigated; we aimed to investigate this using the Surveillance, Epidemiology, and End Results (SEER) database. Methods: We included 39,910 patients from the SEER database treated for M1b NSCLC from 2010-2013. We identified patients with metastatic disease in the brain, lung, liver, and bone. We used Kaplan-Meier analyses and Cox proportional hazards models to assess the impact of varying sites of metastatic disease on overall survival (OS). Results: Patients with disease coded as in the brain without other disease in the lung, liver, or bone had improved OS relative to all other comers with M1b disease (HR = 0.84, 95% CI, 0.84-0.90, P< 0.001). Likewise, patients with disease coded as in the bone without other disease in the lung, liver, or brain had improved OS relative to all other comers with M1b disease (HR = 0.89, 95% CI, 0.86-0.92, P< 0.001). Conclusions: This hypothesis-generating analysis suggests that patients with limited metastatic NSCLC to the bone or brain may particularly benefit from aggressive upfront therapies.