Impact of whole brain radiation therapy on CSF penetration ability of Icotinib in EGFR-mutated non-small cell lung cancer patients with brain metastases: Results of phase I dose-escalation study

•First phase I trial of icotinib combined with whole brain radiotherapy.•First clinical trial about the effect of WBRT on CSF penetration of icotinib.•The maximum tolerated dose of icotinib combined with WBRT is 375mg tid.•CSF concentration and penetration rate of icotinib have a potential ceiling effect.•WBRT may be not able to increase the CSF penetration rate of icotinib till 4 weeks after the treatment.