The mean mRNA value of IGFBP7 expression in cancer cells isolated from treatment-naïve pleural effusions (n = 8) (0.114 ± 0.059) was significantly lower than that after acquired resistance to EGFR-TKI treatment (n = 16) (1.18 ± 0.412; p = 0.0212, by Student’s t-test). The gene discussed is EGFR; the disease is Pleural effusion.