12 November 2018 - Amgen's recent submission for blinatumomab (Blincyto) treatment of patients with B-cell precursor acute lymphoblastic leukaemia in haematological complete remission with minimal residual disease following chemotherapy was based on a propensity score indirect analysis of one single arm blinatumomab study (BLAST) and one retrospective historical control cohort study of patients receiving treatment with standard of care chemotherapy.
This is the first time the PBAC has considered such an approach.
The PBAC noted and agreed with the key issues raised by the commentary and the ESC about the reliability of the indirect comparison including the high risk of bias of the propensity score analysis.
"The results from the average treatment effect of the treated weights (ATT) method were used as the primary analysis in the submission (and economic model) despite the alternative method, average treatment effects (ATE), resulting in better-matched covariates and a smaller extent of data loss. The PBAC noted that the rationale provided in the pre-PBAC response for using the ATT analyses was that it adjusts the control population so it looks similar to the treated population, which the pre-PBAC response stated was “more likely to reflect the treated population in the real-world setting”. However, the PBAC considered that this was not a reasonable premise for using the ATT analysis given that the proposed restriction is much broader than the patients selected for inclusion in the analysis. The PBAC considered that, of the two methods presented, the ATE analysis would have been the more appropriate primary analysis, and to inform the economic model."