Inclusion Criteria:

1. Age >18
2. Histologically or pathologically proven non-small cell lung cancer (NSCLC)
3. Leptomeningeal carcinomatosis confirmed by CSF cytology
4. A patients with EGFR mutation (including exon 19 deletion, L858R)
5. ECOG performance status 0-3
6. Expected life time more than at least 4 weeks
7. A patients who signed the informed consent prior to the participation in the study
8. Chemotherapy-naïve patient is eligible
9. Previous EGFR TKI is allowed if this drug was not specifically used for CNS metastases

Exclusion Criteria:

1. A pregnant or lactating patient
2. A patient of childbearing potential without being tested for pregnancy at baseline or with a positive test. (A postmenopausal woman with the amenorrhea period of at least 12 months or longer is considered to have non-childbearing potential.)
3. A man or woman of childbearing potential without the willingness to use a contraceptive measures during the study
4. A patient with history of another malignant disease within past 3 years, except curatively treated basal cell carcinoma of the skin, cervical carcinoma in situ, and early gastric cancer
5. A patient with active interstitial lung disease, except simple lymphangitic lung metastasis
6. A patient with history of allergic reaction to gefitinib or erlotinib

7. The following laboratory test results:

   • Number of absolute neutrophils counts (ANC) < 1.0ⅹ109/L
   • Number of platelets < 50 ⅹ109/L
   • AST, ALT > 2.5 ⅹupper limit of normal
   • Total bilirubin > 1.5 ⅹupper limit of normal
   • Serum creatinine > 1.5 ⅹupper limit of normal

8. A patient with serious disease as followings

   • Uncontrolled cardiac arrhythmia
   • History of myocardial infarction within 6 months prior to the initiation of study
   • Neurological or psychiatric disorder including dementia or uncontrolled seizure
9. A patient who refused to sign the informed consent