58. CLINICAL PRESENTATION AND IMAGING CHARACTERISTICS OF LEPTOMENINGEAL CARCINOMATOSIS (LC) IN PATIENTS WITH EGFR MUTATED NON-SMALL CELL LUNG CANCER (NSCLC)

BACKGROUND: LC is a late and often fatal manifestation of advanced EGFR mutated NSCLC with up to 9% of patients developing LC. Given the higher incidence of LC in EGFR mutated tumors, we hypothesized it may have unique imaging and clinical characteristics. METHODS: We identified 23 patients with EGFR mutated NSCLC and LC treated at a large academic institution between 2016 and 2019. Clinical and treatment characteristics were obtained from the electronic medical record. Radiographic subtype of LC and presence of ventriculomegaly were determined by independent review of available brain and spine MRI imaging. RESULTS: Among 23 eligible patients, mean age was 57 years, 96% had advanced NSCLC at diagnosis and 61% had EGFR exon 19 deletion. Median time from NSCLC diagnosis to LC development was 23 months (95% CI:13–33), with only 17% of patients presenting with LC in the absence of parenchymal brain metastases. Of the 91% of patients with radiographic evidence of LC, equal numbers had nodular or linear LC (22% each) and 39% had a mixed presentation. Additionally, 30% of patients had evidence of spinal LC. Ventriculomegaly was present in 52% of patients, with 48% developing clinical symptoms of hydrocephalus and 13% receiving shunt placement. Median overall survival (OS) from time of LC diagnosis was 3.9 months (95% CI:2.7–10.0), which is lower than in prior published studies. Patients with nodular LC and absence of ventriculomegaly fared better with a median OS of 6.5 months and 5.7 months respectively. CONCLUSIONS: OS is poor in patients with LC associated with EGFR mutated NSCLC, although appears better in patients with nodular LC. The high incidence of hydrocephalus emphasizes the need for its early recognition and treatment. Further studies are needed to identify promising treatment strategies and to determine factors associated with improved OS in this population.