Non-small cell lung cancer (NSCLC) case study examining whether results in a randomized control arm are replicated by a synthetic control arm (SCA).

Abstract

9108 Background: The FDA’s accelerated approval (AA) pathway provides conditional approval for an investigational product (IP) after positive effect on a surrogate endpoint has been provided, allowing patients earlier access to the therapy. Confirmation of a positive effect on the clinical endpoint after conditional approval is required and usually includes a randomized trial. However, such a trial is challenged by availability of the IP outside the trial. Recruitment becomes more difficult, and patients assigned to control are more likely to drop-out and use the non-assigned IP, which may bias the observed treatment effect. In AA settings we propose a SCA composed of patient level data from previous clinical trials to augment or replace the randomized control. Validity of this approach in one case study is assessed by examining if a SCA can replicate the outcomes of a target randomized control (TRC) from a recent NSCLC trial. Methods: The patients for the NSCLC SCA were required to have satisfied the key eligibility criteria of the target trial and were further selected using a propensity score-based approach to balance the baseline characteristics in the SCA and TRC. All patient selections were made without knowledge of patient outcomes. Results: The results show comparable balance in observed baseline characteristics of the SCA and TRC was achieved. Overall survival (OS) in TRC was replicated by SCA. The Kaplan Meier curves for OS in the SCA and TRC visually overlap. In addition, the log rank test (p = 0.65) and hazard ratio of 1.04 (95% CI: (0.88, 1.23)) were not statistically significant. Conclusions: If the SCA had been in place of the randomized control in this study, conclusions about the treatment effect would have been the same. While this may not hold when it is not possible to balance the groups on all confounders, this suggests that in some settings, SCA could augment or replace the randomized control in future trials easing recruitment, retention, and crossover challenges without compromising the understanding of the treatment effect. Future work should examine in what settings SCA is appropriate and consider the implications of potential unobserved confounders.