MA13.03 Retrospective Study of Intrathecal Therapy for Non-Small Cell Lung Cancer (NSCLC) Patients with Leptomeningeal Carcinomatosis

Abstract

Leptomeningeal carcinomatosis (LMC) is a devastating cancer-related neurological complication with poor prognosis. In EGFR-mutant (mut) NSCLC patients (pts), osimertinib achieves high penetration into cerebral-spinal fluid (CSF) and promising efficacy. However, for EGFR-mut T790M-negative pts treated with prior 1st- and 2nd-generation tyrosine kinase inhibitors (TKI) and for driver negative NSCLC pts, a combination of intrathecal therapy (IT) and systemic therapy (ST) seems to be an appropriate approach. Our purpose is to explore the clinical outcome of IT combined with ST among NSCLC with LMC depending on EGFR status. NSCLC pts with LMC treated with IT in our institution between 2010 and 2018 were retrospectively studied. After LMC diagnosis, intrathecal methotrexate (scheduled: 12mg twice weekly for 4 weeks, then 12mg weekly for 4 weeks) was given in combination with ST. A Kaplan-Meier survival analysis was performed for overall survival (OS) and progression free survival (PFS). A total of 39 pts were included. Patient’s clinical characteristics are summarized in table 1. EGFR status was 17 mut (del19: 11pts); 11 wild-type (wt) and 11 unknown (unk). LMC and NSCLC diagnosis were more likely to be synchronous in EGFR wt compared with EGFR mut. The median follow-up from LCM diagnosis was 10.2 months. At the time of this analysis, only 6 pts were alive. Thirty-two pts received ST in combination with IT, 18 (46%) pts chemotherapy (6wt/ 3mut/ 9unk), while 14 (36%) pts an EGFR TKI (1wt/ 13mut). Clinical response (improvement of neurological symptoms and/or KPS) was seen in 11 (65%) EGFR mut pts vs 2 (18%) wt pts (p=0.033). Median OS and PFS for the whole cohort were 23 weeks (95%CI, 8.1 to 37.9) and 10 weeks (95%CI, 7.1 to 12.8) respectively. Median OS was higher for EGFR mut pts compared to wt pts, 38 weeks (95%IC 13.6-62.4) and 19 weeks (95%IC, 4.06-33.9) respectively, however this difference was not statistically significant (p=0.36) probably due to lack of statistical power. Methotrexate-based IT given concurrently with systemic TKI may confer a higher clinical benefit and a trend toward OS benefit in NSCLC patients with LCM and EGFR activating mutations.