Extracranial metastasis sites correlate to the incidence risk of brain metastasis in stage IV non-small cell lung cancer: a population-based study

PurposeThe aim of this study was to analyse the correlation of extracranial metastasis sites (ECMs) to the incidence risk of brain metastasis (BMs) in stage IV non-small cell lung cancer (NSCLC).Methods18349 newly diagnosed patients were retrospectively analysed, and 4919 pairs of cases were matched by propensity score matching in a 1:1 ratio. Alternative factors were analysed by multivariable logistic regression analysis. And the interaction analysis and subgroup analysis were carried out.ResultsThe incidences of Brain, Lung, Liver, Bone, Multiple and Other metastasis were 26.9%, 20.2%, 4.6%, 19.9%, 16.9% and 38.3%, respectively. Results suggested that Age, Race, Histological type, Grade, T stage, N stage and Organ metastasis site were risk factors (p < 0.05). The interaction analysis suggested interaction effects between the Primary site, T stage, N stage and Organ metastasis site. The subgroup analysis showed that the Organ metastasis site and the risk of BMs were statistically significant except that the Overlapping subgroup (p = 0.267) of the Primary site. And the incidence risk of BMs in Lung metastasis, Liver metastasis and Bone metastasis groups was lower than that in other metastasis group (OR 1, p < 0.05). There was no significant difference between the Multiple metastasis group and the other metastasis group (OR 1.091, p = 0.169).ConclusionAdvanced age, non-Asian/Pacific Islander, non-squamous cell carcinoma, poorly differentiated grade, and higher T/N stage were risk factors for increased BMs in stage IV NSCLC, and the ECMs were associated with the risk of BMs.