Estimating long-term survival of previously untreated patients with EGFR mutation-positive (EGFRm) advanced non-small cell lung cancer (NSCLC) who received osimertinib in the FLAURA study.

e20560 Background: In the Phase III FLAURA trial (NCT02296125), osimertinib, a third-generation EGFR-TKI, provided clinically and statistically significantly longer progression-free survival versus gefitinib/erlotinib as first-line treatment for patients with EGFRm advanced NSCLC. At the time of analysis, data on overall survival (OS) were immature (25% maturity). To better understand the long-term survival potential of osimertinib beyond the observed trial follow-up period, mathematical parametric survival models were used to estimate clinically plausible survival rates up to 5 years from FLAURA. Methods: Following published best-practice guidelines, candidate parametric survival models were evaluated based on both statistical and visual goodness-of-fit to the observed FLAURA OS data. Two modeling approaches were considered: single models with treatment included as a covariate; and separate models fitted to the osimertinib and gefitinib/erlotinib arms. Point estimates of 5-year survival rates with 95% confidence intervals (CIs) are reported for the best fitting model. Results: The best fitting parametric survival model to the FLAURA OS data was the Weibull model with treatment included as a covariate. Based on this model, estimated median OS was longer with osimertinib than with gefitinib/erlotinib (41.4 months vs 30.6 months). The estimated 3- and 5-year survival rates with osimertinib were 57.3% (95% CI 46.6%, 69.2%) and 31.1% (95% CI 23.7%, 41.8%), respectively. In comparison, the estimated 3- and 5-year survival rates with gefitinib/erlotinib were 41.1% (95% CI 31.9%, 52.9%) and 15.5% (95% CI 11.6%, 22.1%), respectively. Conclusions: Based on the best fitting parametric survival model to FLAURA OS data, the estimated 5-year survival rate with osimertinib was double that with gefitinib/erlotinib (31.1% vs 15.5%) in patients with EGFRm advanced NSCLC. Long-term follow-up data from FLAURA (60% OS maturity) will further validate this finding. Clinical trial information: NCT02296125.