Simple SummaryGenetic information is essential before starting the treatment of advanced-stage non-small-cell lung cancer (NSCLC) and in the adjuvant setting (EGFRmutation status only) after pulmonary resection of early-stage NSCLC. Several genetic tests for NSCLC are available, which vary in turnaround time and cost (usually higher costs for multi-gene tests). The Idylla™ EGFR Mutation Test is an ultra-rapid single-gene test used to detectEGFRmutations. In this study, we compared the performance of the Idylla EGFR Mutation Test with the current standardEGFRsingle-gene test (Cobas®EGFR Mutation Test v2) and demonstrate the accuracy of the Idylla EGFR Mutation Test as a molecular screening platform. From these data, we propose genetic testing strategies that may reduce the costs and shorten the turnaround time in advanced-stage NSCLC and in the adjuvant setting after pulmonary resection of early-stage NSCLC.AbstractBackground: The Idylla™ EGFR Mutation Test is an ultra-rapid single-gene test that detects epidermal growth factor receptor (EGFR) mutations using formalin-fixed paraffin-embedded specimens. Here, we compared the performance of the Idylla EGFR Mutation Test with the Cobas®EGFR Mutation Test v2. Methods: Surgically resected NSCLC specimens obtained at two Japanese institutions (N = 170) were examined. The Idylla EGFR Mutation Test and the Cobas EGFR Mutation Test v2 were performed independently and the results were compared. For discordant cases, the Ion AmpliSeq Colon and Lung Cancer Research Panel V2 was performed. Results: After the exclusion of five inadequate/invalid samples, 165 cases were evaluated.EGFRmutation analysis revealed 52 were positive and 107 were negative forEGFRmutation in both assays (overall concordance rate: 96.4%). Analyses of the six discordant cases revealed that the Idylla EGFR Mutation Test was correct in four and the Cobas EGFR Mutation Test v2 was correct in two. In a trial calculation, the combination of the Idylla EGFR Mutation Test followed by a multi-gene panel test will reduce molecular screening expenses if applied to a cohort withEGFRmutation frequency >17.9%. Conclusions: We demonstrated the accuracy and potential clinical utility of the Idylla EGFR Mutation Test as a molecular screening platform in terms of turnaround time and molecular testing cost if applied to a cohort with a highEGFRmutation incidence (>17.9%).