Background: Data on EGFRm in early stage NSCLC are limited. RADIANT was a prospectively randomized Phase 3 trial of adjuvant erlotinib (E) v placebo (P) in 973 patients (pts) with completely resected Stage IB–IIIA NSCLC that was EGFR +ve by IHC or FISH (ASCO14 #7501; ESMO14 #1178PD). Methods: EGFRm in exons 18–21 was determined by WAVE HS and confirmed by Sanger sequencing. Two EGFRm groups were defined: Common refers to exon del19 or L858R irrespective of the presence of another EGFRm; Rare Only refers to EGFRm without del19 or L858R. Exploratory analysis of disease-free survival (DFS) was performed by subgroup (June 11, 2014 data cutoff). Results: 921 pts had EGFRm status determined; 198 pts (21.5%) had EGFRm (161 Common, 37 Rare Only). There was no sex difference between the groups, but pts with Rare Only EGFRm were less likely to be Asian (32.4% v 47.2%) or non-smokers (48.6% v 62.7%). With a median follow-up of 5 years, updated DFS by mutation type is shown below. The DFS HR was lower in the Common group (HR [E/P] 0.75, CI 0.48, 1.16) than in the Rare Only group (HR 1.19, CI 0.44, 3.22). Conclusions: The effect of E on DFS in EGFRm subgroups remains inconclusive. Clinical trial information: NCT00373425

NR = Not Reached. *Includes 12 pts with another EGFRm in addition to del19 or L858R. + Indicates censoring; **Pts may have > 1 rare EGFRm.