Background: Although osimertinib has become standard first-line (1L) therapy for patients (pts) with EGFRm mNSCLC, a subset treated with earlier-generation EGFR-targeted TKIs and chemotherapy have had long-term survival. We sought to characterize clinical features of long-term survival in pts with EGFRm mNSCLC treated prior to the osimertinib era. Methods: Data were abstracted from electronic medical records at 12 cancer centers participating in the Academic Thoracic Oncology Medical Investigator’s Consortium (ATOMIC). We included patients with mNSCLC with sensitizing mutations in EGFR who started 1L systemic therapy before 2015. Survival distributions and predictors were assessed using Kaplan-Meier estimates and a multivariable Cox proportional hazards model including time-dependent brain metastasis (met) development, age, 1L therapy (targeted vs. chemotherapy), sex, race, and smoking status. Multivariable logistic regression was used to evaluate baseline predictors associated with 5+ year survival vs. not for those with known survival status at 5 years after start of 1L. Results: We identified 304 patients (69% female, 56% White, 29% Asian, mean age 61.2). First-line targeted therapy was given in 70% of patients. With a median follow-up of 81.5 months, median overall survival was 63.5 months (95% CI 59.4-71.9). 135 (44%) pts survived 5+ years; among those with baseline next-generation sequencing (NGS), presence of a baseline pathogenic ERBB2 variant was higher in 5+ year survivors (4/51 [8%], 2x amplification, y772_A775dup, S310F) v others (1/65 [2%], amplification). Among 161 pts with baseline brain imaging, both baseline and on-treatment development of brain mets were associated with worse survival (HR 1.29, 95% CI 1.21-1.37; HR 1.59, 95% CI 1.47-1.72; both P < 0.001). Excluding 22 patients lost to follow-up before 5 years, a history of smoking (OR 2.99, 95% CI 1.35-6.90, P = 0.008) and baseline brain metastases (OR 3.57, 95% CI 1.64-8.13, P = 0.002) were associated with death before 5 years. Conclusions: Long-term survivors with EGFRm mNSCLC treated before the osimertinib era were more likely to be nonsmokers and have no baseline brain metastases. This highlights a subset of EGFRm patients who had excellent outcomes with older treatment strategies and may not benefit as much from intensification approaches. Additional baseline mutational data will be presented at the conference.