P1.16-02 The Real-World Risk of Brain Metastases in Stage 3 Lung Cancer Patients in the Era of PET and MRI Staging

Abstract

Brain metastases (BMs) are a common site of recurrence in Stage 3 NSCLC following definitive chemoradiation. In small-cell lung cancer, prophylactic cranial irradiation (PCI) was historically offered to improve overall survival (OS). Studies of PCI in NSCLC failed to show OS benefit; many were based on a 30% 2-year risk of CNS metastases, using data from the era prior to routine brain imaging at staging. An increasing preference for stereotactic radiosurgery (SRS) over WBRT for BMs may also affect outcomes. The purpose of this study was to review surveillance, incidence, and treatment patterns of BMs in patients with stage 3 NSCLC at our institution. In this IRB approved study, we retrospectively reviewed stage 3A/3B NSCLC patients treated at Stanford from 2008-2018. Of 279 patients, 163 received radiation with curative intent, and had complete data regarding pathology, staging, imaging, radiation and follow-up. Ninety-seven patients had adenocarcinoma, 54 squamous, and12 other histology (usually large-cell neuro-endocrine). Two patients received PCI; neither developed BMs. For all patients, median survival was 50 months (95%CI:30, 61). Patients with adenocarcinoma had significantly longer survival than squamous (53 v. 24 months, p=0.0119). 37 patients (22.7%) developed BMs, with 2-year cumulative incidence of 17.1% (95%CI:11.6%, 23.5%). Patients with adenocarcinoma had higher cumulative incidence of BM at 2 years, 21.9%, versus squamous 7.9%, and other histology 21.7%(p=0.0295). Of 37 BM patients, 18 presented with one BM, 8 with 2-3, and 11 had >3 BMs. Seventeen patients had asymptomatic BMs discovered at re-staging for systemic recurrence, 3 patients had asymptomatic BMs on surveillance MRI, 14 had BMs on MRI ordered for neurologic symptoms, 3 had symptoms and pre-scheduled surveillance MRI confirmed BM. Twenty-nine patients received SRS for first BM, 3 received WBRT, 5 had no treatment. Time from first BM to death was not different between adeno and squamous histology (21.0 v. 16.5 months, p=0.6050) or symptomatic v. asymptomatic BMs (18 v. 21 months, p=0.8273). Patients with stage 3A/3B NSCLC treated at our institution have a lower 2-year incidence of BMs than historically reported, but higher than recently reported in the PACIFIC study (11.8%, 25-month median follow-up). Suspicion for BM should remain high in this population. Our experience suggests imaging at the time of systemic recurrence or neurologic symptoms may capture the majority of brain metastases. Routine surveillance MRI may capture more asymptomatic metastasis, though impact on overall survival remains unclear.