Leptomeningeal metastasis (LM) is one of the disastrous events when managing advanced Non-small cell lung cancer (NSCLC) due to a grave prognosis. Although intrathecal (IT) chemotherapy and brain and/or spinal axis irradiation show some effects for LM in advanced NSCLC, the prognosis is still poor with median survival less than 12-14 weeks. Epidermal growth factor (EGFR) tyrosine kinase inhibitors (TKIs) showed to be effective for LM in selected NSCLC patients in some retrospective research. Our single-center prospective research indicated that the incidence of EGFR sensitive mutations (EGFRm+) in NSCLC-LM patients was high and EGFR-TKIs showed a survival benefit for LM in EGFRm+ NSCLC patients. A multi-center prospective observational biomarker study will be started in 11 lung cancer center based on our single-center prospective research result. The aims of the study are to find predictive biomarkers for LM in advanced NSCLC, to establish EGFR-TKIs based comprehensive treatment for appropriate EGFRm+ LM cases, and to establish effective clinical assessment criteria for NSCLC-LM EGFR-TKIs treatment.

Inclusion Criteria:

1. The cytological identification of malignant cells within cerebrospinal fluid (CSF).
2. Non-small cell lung cancer patients.
3. Tumor specimens or cytology specimens can be used for the EGFR gene mutation detection.
4. The entails examining cerebrospinal fluid could be obtained by lumbar puncture.
5. Expected survival time is greater than 1 month.

Exclusion Criteria:

Patients with radiologic evidence of LM not confirmed by positive CSF cytology.

Leptomeningeal metastasis (LM) in patients with non-small cell lung cancer (NSCLC)