MA04.07 Comparative Clinical Outcomes for Patients with NSCLC Harboring EGFR Exon 20 Insertion Mutations and Common EGFR Mutations

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Conference Proceeding

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Publication Title

Journal of Thoracic Oncology


Introduction: Approximately 85–90% of the mutations seen in EGFR-mutant non-small cell lung cancers (NSCLCs) are common mutations (cEGFR), Exon 19 deletions and Exon 21 L858R. Up to 10% of EGFR-mutant NSCLC harbors Exon 20 insertion mutations (Exon20ins). We conducted a retrospective cohort study using real-world data to compare clinical outcomes between patients harboring Exon20ins and cEGFR.

Methods: This retrospective cohort study included patients from the Flatiron Health database (1 January 2011 through 31 May 2020) who had advanced NSCLC. The objectives of the study were to assess the prognostic value of Exon20ins compared with cEGFR (start date of first-line therapy as the index date) and the effect of tyrosine kinase inhibitor (TKI) treatment between the groups (start date of first TKI line as the index date). Analysis was stratified by line of TKI use. Endpoints included real-world overall survival (rwOS), progression-free survival (rwPFS), and time to next therapy (rwTTNT) and were analyzed using multivariable Cox proportional hazards model and summarized by Kaplan-Meier method.

Results: Among 62,464 patients with advanced NSCLC, 181 with Exon20ins and 2833 with cEGFR met eligibility criteria. Population demographics between the groups were comparable with minor exceptions. With median 34-month follow-up, Exon20ins was associated with a 75% increased risk of death (adjusted hazard ratio [adjHR] of 1.75 [95%CI, 1.45–2.13]; p˂0.0001); median rwOS was 16.23 (95%CI, 11.04–19.38) for Exon20ins and 25.49 months (95%CI, 24.48–27.04) for cEGFR (Table). The estimated 5-year survival rate for Exon20ins is 8% compared with 19% for cEGFR. The predictive value of TKI treatment, stratified by line, was assessed in 76 Exon20ins and 2749 cEGFR patients who were treated with TKIs. With median 20.6-month follow-up, there was a 170% increase in risk of progression or death associated with Exon20ins (adjHR of 2.7 [95% CI, 2.06–3.55]; p˂0.0001); median rwPFS was 2.86 months (95%CI, 2.14–3.91) compared with 10.45 months (95%CI: 10.05–10.94) for cEGFR. Furthermore, there was a 170% increased risk of death (adjHR of 2.70 [95% CI, 2.04–3.57]; p˂0.0001) associated with Exon20ins; median rwOS was 7.46 months (95%CI, 5.45–13.34) for Exon20ins and 25.49 months (95%CI, 24.28–26.81) for cEGFR (Table).

Conclusion: Patients with Exon20ins have a worse prognosis compared with patients with cEGFR. Furthermore, EGFR TKI treatment was substantially less effective for patients with Exon20ins, as the risk of disease progression and mortality was higher compared with patients with cEGFR. These findings highlight the need for new treatment options for Exon20ins.





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