Project Switch: Lenalidomide And Dexamethasone (Len-Dex) As A Potential Synthetic Control Arm (Sca) In Relapsed Or Refractory Multiple Myeloma (Rrmm).

8047 Background: Len-Dex is a common comparator arm to test novel therapies in rrMM trials. There is interest in evaluating if the control data from one clinical trial can be borrowed to another clinical trial, thus creating SCAs which could potentially improve accrual to trials, make better go/no-go decisions, and increase patients access to promising experimental therapies (ETs). We looked at legacy rrMM trials to assess the impact of switching and pooling Len-Dex control arms among different trials when evaluating ETs. Methods: We identified 4 contemporary rrMM trials that enrolled 2,729 patients testing ET + Len-Dex vs. Len-Dex alone. We calculated progression-free survival (PFS), Hazard Ratio (HR) and 95% Confidence Interval (CI) for ET compared to the original trial control, the switch Len-Dex controls, a pooled Len-Dex control, and a matched pooled control using bootstrapping sampling methods to match the experimental arm baseline demographics and prior lines with the pooled control. Results: See table. Conclusions: In this analysis, the switch and pooled controls matched the original control for Trials 1 and 2, but not for Trials 3 and 4. The bootstrapping methods did not substantially assist in replicating the original results. This could be due to several factors including heterogeneity of the enrolled populations including different lines of therapy, different pharmacologic classes of drugs studied in the ETs, and missing prognostic data including cytogenetics. Further investigations into propensity score matching will be explored to determine if SCAs can be improved.[Table: see text]