P11.07.B MR IMAGING FOR INITIAL DIAGNOSIS OF LEPTOMENINGEAL METASTASES FROM SOLID CANCERS: AN EXPLORATORY DATA ANALYSIS OF 227 PATIENTS IN A SINGLE INSTITUTE

Abstract BACKGROUND Leptomeningeal metastasis (LM) is a life-threatening and quickly advancing complication in patients with solid cancers. Reliable and rapid initial diagnosis is a challenge to this urgent disease. Magnetic resonance (MR) imaging is characterized by less-invasiveness and immediate information including patterns of LM spread, brain parenchymal metastases (PM), and hydrocephalus. The priority of MR imaging remains controversial in initial diagnosis and decision-making for patients with LM. MATERIAL AND METHODS After approval by the Institute Review Board, retrospective search was conducted on 227 patients with LM who underwent consultation in the CNS Cancer Board between 2007 and 2023. Data on patient characteristics, MR findings (conventional postcontrast T1-weighted images at 1.5 or 3T), and outcomes were collected. Statistical analyses were performed using the chi-squared test, Kaplan-Meier estimates, log-rank test, and multivariate Cox regression analysis. RESULTS Primary cancers included lung (66%), breast (15.9%), and gastrointestinal (GI) cancers (12.8%). The mean follow-up duration was 8.6 months. The median OS from the diagnosis of LM was 3.8 months [95%CI: 3.3-4.5]. All patients underwent MR imaging, and 47.1% CSF cytology test. Initial diagnosis of LM was made via MR imaging and neurological manifestations in 98.2% of patients, and via CSF cytology alone in 1.8%. Postcontrast MR images showed mixed pattern in 43.6% of cases, linear in 41.9%, nodular in 8.8%, or no enhanced lesions in 5.7%, also hydrocephalus in 39.2%. PM developed in 52.9% of LM patients, of whom 11.5% had pre-existed PM (prePM), 41.4% had concurrent PM (conPM), and 47.1% LM only. MR mixed pattern made up 81.9% in conPM group, linear pattern 76.6% in LM only group, however, no dominant pattern was observed in prePM group (P<0.001). OS was not significantly different among the prePM, conPM or LM only groups (P=0.301). By multivariate analysis, prognostic factors for longer OS included age younger than 60 years (HR0.67 [95%CI: 0.46-0.96] p=0.030), lung cancer compared with breast cancer (HR0.62 [95%CI: 0.42-0.94] p=0.023), and synchronous LM at the diagnosis of primary cancer (HR0.49 [95%CI: 0.31-0.78] p=0.002). Factors for significantly increased mortality included GI cancer compared with breast cancer (HR2.13 [95%CI: 1.26-3.60] p=0.005), mixed pattern compared with nodular one (HR1.68 [95%CI: 1.01-2.79] p=0.047), and hydrocephalus (HR1.44 [95%CI: 1.08-1.94] p=0.015). CONCLUSION This study showed that MR imaging demonstrates worse outcomes in LM with mixed pattern, and that it immediately offers diagnosis of associated hydrocephalus and concurrent PM that need urgent treatment decisions. Further research is required to specify a less-invasive and in combination with biomarker-driven approach to LM.