Abstract PO1-11-02: Reporting of Post-protocol Therapies in Metastatic Breast Cancer Registration Clinical Trials: A Systematic Review

Abstract BACKGROUND As the treatment for metastatic breast cancer (MBC) often includes sequential lines of therapy, data on post-protocol treatment in clinical trials are valuable in the assessment of long-term outcome. The objective of this study was to assess the reported data on post-protocol therapy in clinical trials supporting US Food and Drug Administration (FDA) approval of drugs for MBC. METHODS We identified all initial and subsequent published trials supporting FDA approved indications for MBC between 1/2000-2/2023. Collected data included study design, patient characteristics and whether reporting on post-protocol therapy was available. Differences in study design and population between studies with and without data on post-protocol therapy were evaluated. FINDINGS A total of 41 indications for MBC were identified. Supporting studies comprised 20,152 patients. Data were evaluated from 241 publications or abstracts. Reporting of post progression therapy was available for 21 (51%) indications. Of these, post-progression therapy data were often partial and the appropriateness of the therapy could not be evaluated. At the time of FDA approval, data on overall survival (OS) were reported only in 17 (41%) studies. Of these, in 8 studies OS was significantly improved, in 7 studies OS was not improved and 2 studies were single arm. Differences between studies with and without data on post progression therapy are presented in the Table. Studies with OS as their primary endpoints were associated with significantly higher reporting of post-protocol therapy, while studies with both OS and progression free survival (PFS) as their primary endpoint had low reporting rate. There were no other statistically significant differences. Reporting post-protocol therapy has not changed over time with reported data in 50% and 52% studies between 2000-2010 and 2011-2023, respectively. CONCLUSIONS Data on post progression therapy in trials supporting FDA approval of drugs for MBC are available in fewer than half of indications. Reported data are often partial and may not include sequential therapies consistent with standard of care. As subsequent lines of therapy may have a crucial role in patients' outcome, post protocol reporting should be included in the regulatory submission and be made available publicly. Differences between studies with and without data on post progression therapy Citation Format: Shlomit Shachar, Yasmin Korzets, Daniel Shepshelovich, Noa Zlotchover, Eitan Amir, Ariadna Tibau, Hadar Goldvaser. Reporting of Post-protocol Therapies in Metastatic Breast Cancer Registration Clinical Trials: A Systematic Review [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-11-02.