P75.20 Outcomes of Lung Cancer Patients with Leptomeningeal Metastases Following Immune Checkpoint Inhibitor Treatments: A Pooled Analysis

Abstract

Leptomeningeal metastases (LM) occur in up to 5% of non-small cell lung cancer (NSCLC) with a higher prevalence in EGFR-mutated patients. Immune checkpoint inhibitors (ICIs) have become pivotal treatments in NSCLC but its role in LM patients, whose overall survival (OS) is dismal, hasn’t been comprehensively reported. We collected LM patients treated with ICIs in Guangdong Lung Cancer Institute and reviewed published literature to obtain clinical characteristics and outcomes of these patients. Thirty-two patients received ICIs after diagnosis of LM (7 from our institute, 25 from 6 published literature). ALL leptomeningeal involvements were cytologically confirmed or radiologically diagnosed in brain MR except that 1 was based on typical neurologic symptoms. The median age was 55 (range 34-80). Two thirds of them were former or current smokers. Druggable genes (EGFR/ALK/BRAF/MET/ERBB2) were detected in 37.5% of all patients. Six patients showed high PD-L1 expression (80-100%) and 7 patients expressed low PD-L1 protein (≤20%). Before ICI treatments 65.6% and 31% received brain irradiation and steroid respectively. ICI regimens were nivolumab (n=21), pembrolizumab (n=9) and atezolizumab (n=2) monotherapy or combinational therapy with chemotherapy and anti-angiogenic drug. All patients received ICIs as the second or subsequent line. The median time between diagnosis of LM and ICI treatments was 1.9 months (range 0-21.9 months). Finally 62.5% patients experienced improvement or stabilization of neurologic symptoms. As to tumor response, 2 patients had complete response and 3 partial response (systemic evaluation). The median progression free survival (PFS) was 2.5 months (95% CI, 1.7-3.3 months) and OS was 5.4 months (95% CI, 1.9-8.9 months). Three patients achieved remarkable PFS of more than 20 months. Clinical factors like gender, smoking status, PD-L1 expression seemed not to impact PFS and OS except that improvement of neurologic symptoms at the start of ICIs seemed to indicate both prolonged PFS and OS (P=0.002, P=0.024). ICIs should be discussed in the treatment of advanced lung cancer patients with leptomeningeal metastases when therapy option is limited in this population.