NEIM-01 INCIDENCE AND DIAGNOSTIC TECHNIQUES FOR LEPTOMENINGEAL DISEASE IN PATIENTS WITH BRAIN METASTASIS

BACKGROUND: Leptomeningeal disease (LMD) is malignant infiltration of the pia mater and cerebrospinal fluid (CSF) space. LMD carries a poor prognosis with median survival of a few months. Annually, 110,000 patients in the United States are diagnosed with LMD. The incidence is rising because of improvements in control of primary cancers and recognizing that LMD is a late sequelae of some malignancies. Definitive diagnosis of LMD is made by CSF cytology and/or spine MRI, although neither tool shows robust sensitivity. The diagnostic challenges for LMD have led to a lack of uniformity in the diagnostic approach. METHODS: A systematic chart review of brain metastasis patients was conducted at Froedtert Hospital between 2019-2021. Information on primary cancer, LMD suspicion, work up, confirmation, treatment, and survival were collected and analyzed. RESULTS: Among 151 patients with brain metastasis, 86 were suspected and 29 were confirmed to have LMD. Of the confirmed patients, the most common primary cancers were lung (n=8, 27.6%) and breast (n=8, 27.6%). Most patients (n=24, 82.8%) underwent both LP and MRI. LMD was confirmed by positive cytology in a minority of cases (n=9, 31%), with most patients being confirmed by positive MRI or clinical findings alone (n=20, 69%). All LPs had over 10 mL of CSF sent to analysis. A median of 2 LPs were required before a positive cytology confirmed the diagnosis. Due to small sample size, no statistical analysis was made to correlate positive LP with primary cancer sites. CONCLUSION: Less than one third of cancer patients with confirmed LMD have positive cytology, despite the majority (>80%) of them undergoing LP. The dissonance between diagnostic strategies and confirmatory results is expected considering the low sensitivity of LPs; however, it highlights the need for more precise diagnostic tools, and development of a data-based strategy for LMD confirmation.