A retrospective review of 25 NSCLC (9 with exon 21 EGFR mutation and 8 with exon 19 deletion) patients with leptomeningeal (LM) carcinomatosis treated with either erlotinib or gefitinib demonstrated that those treated with erlotinib had a cytologic conversion rate of 64.3% compared to 9.1% with gefitinib (38), suggesting greater activity of erlotinib over gefitnib in the setting of LM disease. Here, EGFR is linked to non-small cell lung carcinoma.