Xu Y, et al. - In view of the limitations of traditional imaging tools and lack of standard evaluation criteria in diagnosing and and assessing responses in leptomeningeal metastasis (LM), researchers conducted the first prospective, observational study in 49 cytologically diagnosed non-small cell lung cancer (NSCLC)-LM patients. They assessed LM responses with a composite endpoint assimilating neurological symptoms, cerebrospinal fluid (CSF) parameters and central nervous system (CNS) imaging. They observed that 93.9% of the NSCLC-LM patient cohort carried oncogenic driver mutations. Findings from the present study supported the validity of the composite endpoint for objective response evaluation of LM. Between the primary tumor and CSF, the status of EGFR activating mutations was highly concordant. The present data indicated that T790 M occurrence in CNS lesions was relatively rare and correlated with the intracranial exposure level of EGFR-TKIs.