Prevalence of EGFR mutation testing in early-stage lung cancer: Implications of the ADAURA trial for clinical practice.
Authors: Rodriguez Estelamari , Dawar Richa , Basher Fahmin , Costa Philippos Apolinario , Torres Tisdrey , Nguyen Dao M. , Villamizar Nestor , Lopes Gilberto 
Published: June 2021

e20507 Background: It is reported that about 20% of patients with resected NSCLC adenocarcinoma harbor an EGFR driver mutation in the United States. Up to the recent approval of osimertinib in the adjuvant setting for resected EGFR + NSCLC based on the ADAURA trial, routine molecular profiling of early-stage lung cancer had not been standard of care. We hypothesize that there is a significant proportion of patients with resected adenocarcinoma with unknown EGFR status who could benefit from treatment that are missed with our current testing practices. Methods: We performed a retrospective analysis of Stage IB-IIIA lung adenocarcinomas resected at the University of Miami from 2014 to 2019. Eligible patients were identified from the Cancer Registry and information on EGFR mutation testing and treatment was obtained from chart review. We evaluated the prevalence of EGFR mutation testing in this population and outcomes based on EGFR mutation status. Disease free survival (DFS) and clinico-pathologic characteristics were evaluated. We estimated the number of patients that would have been eligible for EGFR testing and adjuvant osimertinib therapy in the pre-ADAURA era in our patient cohort. Results: A total of 120 patients had resected stage IB-IIIA adenocarcinoma during this five-year period (Stage IB 42.5%; Stage IIA 13.3%; Stage IIB 25%; Stage IIIA 19.2%) with a median age of 66 years. Most were females (59%), NHWs (51.5%), Hispanics (46.9%), and former smokers (66.7%). Out of patients with Stage IB-IIIA NSCLC with adenocarcinoma, 42.5% completed recommended adjuvant platinum-based chemotherapy. Only 40% of patients were referred for EGFR testing during this study period. The prevalence of EGFR mutations in this population was 10.8% (13 /120), but 59% of cases had no available EGFR testing. The most prevalent mutation was L858R (53.8%) followed by exon-19 deletions (30.8%). A total of 6 patients received an EGFR TKI therapy during the follow up period (2 in the adjuvant setting). With a median follow up of 12 mos, the rate of recurrence by stage was: Stage IB (3.9%); Stage IIB (10%); Stage IIIA (13%). Median time to disease progression or death was 13 months in this subgroup. There was no difference in disease free survival for patients with EGFR testing and those without results available in this short follow up period. Conclusions: Based on this retrospective review, up to 60% of patients with early-stage NSCLC with non-squamous histology have no available EGFR testing in the pre-ADAURA era. Of the anticipated 20% of patients with expected EGFR mutations based on historical controls, we have only identified half of patients that would have been eligible for adjuvant osimertinib. This study establishes the importance of upfront EGFR mutation testing in all NSCLC patients, not only to prognosticate, but also to identify the subset of patients who could benefit from adjuvant EGFR therapy.