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

Purpose: The 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).

Methods: 18349 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.

Results: The 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).

Conclusion: Advanced 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.