OTHR-15. PATIENTS WITH LIMITED STAGE SMALL CELL LUNG CANCER THAT RECUR WITH ISOLATED BRAIN METASTASES HAVE PROLONGED SURVIVAL

INTRODUCTION: Small cell lung cancer (SCLC) frequently metastasizes to the brain. In patients with limited-stage disease (disease confined to one radiation portal), the incidence of brain metastasis after 3 years is 50–60%. We reviewed patients with SCLC and hypothesized that isolated brain recurrence has a unique natural history. METHODS: 471 adult SCLC patients seen at University Hospitals Case Medical Center from 1998 to 2014 were screened. Patients were separated by those with isolated brain metastases and those with other patterns of metastasis. Demographic data including age, race, sex, smoking history and clinical data such as TNM classification, stage, treatment, and time to relapse and death were collected. Median overall survival (mOS) and progression free survival (mPFS) were compared using log-rank tests and Kaplan-Meier plots were constructed. In a separate cohort of metastatic SCLC we examined differences in next generation sequencing (NGS) of targeted exomes between primary and metastatic sites including the brain. RESULTS: 281 extensive-stage patients and 40 limited-stage patients were included. 12% (30/281) of the extensive-stage patients and 25% (10/40) of limited-stage patients had isolated brain metastases. Patients with limited-stage disease who developed isolated brain metastases had significantly improved mOS as compared to those who developed other sites of metastasis (OS = 38.7 months vs. 20.2 months, p=0.033). Furthermore, mPFS for limited-stage patients with isolated brain metastases was improved compared to other patterns of metastases (PFS = 17.9 months vs. 10.1 months, p = 0.03). NGS demonstrated that NOTCH1 mutations were infrequent in biopsies from all metastatic sites but were common in primary lung tumors. CONCLUSION: In our single center review, patients with limited-stage SCLC who recurred only in the brain had improved survival as compared to those who had other patterns of metastases. Our initial work demonstrates differences in oncogenic gene mutations between the metastatic and primary tumors.