In a prospective phase II study conducted in Japan that treated EGFR-mutant patients with BM with gefitinib as a first-line therapy followed by WBRT as a salvage therapy, the IC PFS following gefitinib treatment was 14.5 months, the OS was 21.9 months, and the patients showed not only longer survival but also a reduced incidence of cognitive impairment. Here, EGFR is linked to Cognitive impairment.