Assessing the real-world effectiveness of 8 major metastatic breast cancer drugs using target trial emulation☆

Background: Demonstration of trial emulation ability to benchmark randomised controlled trials (RCTs) from real-world data (RWD) is required to increase confidence in the use of routinely collected data for decision making in oncology. Methods: To assess the frequency with which emulation findings align with RCTs regarding effect size on overall survival (OS) in metastatic breast cancer (MBC), 8 of 13 pre-selected pivotal RCTs in MBC were emulated using data from 32,598 patients enrolled in the French ESME-MBC cohort between January 1, 2008 and December 31, 2021. Adjustment methods and confounders were selected a priori for each emulation; stabilized weight was the reference method to mitigate confounding. Concordance in OS hazard ratios with associated 95 % confidence intervals between RCTs and emulations were assessed used predefined metrics based on statistical significance, estimates, and standardized differences. Results: The effect sizes were consistent with RCT results in 7 out of the 8 emulations; 4 emulations achieved full statistical significance agreement; 5 emulations had a point estimate included in the RCT CI (estimate agreement); 6 emulations reported no significant differences between RCT and emulation (standardized difference agreement). Discrepancies related to residual confounders and significant shifts in prescription practices postdrug approval may arise in some cases. Conclusion: Target trial emulation from RWD combined with appropriate adjustment can provide conclusions similar to RCTs in MBC. In oncology, this methodology offers opportunities for confirming the impact on longterm survival, for expanding indications in patients excluded from RCTs and for comparative effectiveness in single-arm trials using external control arms.