Abstract PO3-16-12: European real-world experience of patients with HER2+ advanced/metastatic breast cancer accessing trastuzumab deruxtecan through a named patient program: first interim analysis of EUROPA T-DXd

Abstract Background: In 2021, trastuzumab deruxtecan (T-DXd) monotherapy was conditionally approved in the EU for adult patients with human epidermal growth factor receptor 2-positive (HER2+) advanced/metastatic breast cancer (mBC). A named patient program (NPP) was initiated (March 2021) to enable eligible patients with an unmet medical need to gain access to T-DXd when not yet available locally, either commercially or through an appropriate clinical trial. Centers that treated/are treating patients under this NPP were invited to participate in EUROPA T-DXd real-world data (RWD) collection. Methods: EUROPA T-DXd is an ongoing, multicenter (Ireland, Italy, and Spain), observational (retro- and prospective) study of RWD from approximately 200 adult patients with HER2+ advanced/mBC who had received ≥2 prior anti-HER2 regimens and for whom T-DXd was initiated through the NPP. Collection of RWD is optional and independent of eligibility for the NPP. The primary objective is to estimate real-world time to treatment discontinuation (rwTTD). Secondary objectives include real-world progression-free survival (rwPFS), reasons for T-DXd discontinuation, safety, and prior anti-HER2 treatment patterns. Results: This first interim analysis included 84 evaluable patients. Patients had a mean (standard deviation) age of 53.4 (11.1) years; most were female (97.6%) and had HER2 immunohistochemistry 3+ (70.2%), and 44% had received >3 prior lines of anti-HER2 therapy in the metastatic setting (Table). At data cutoff (June 5, 2023), 50 (59.5%) patients were still receiving T-DXd. In total, 34 patients (40.5%) discontinued T-DXd (death, n=1 [1.2%]; adverse event, n=3 [3.6%]; disease progression, n=26 [31%]; or other, n=4 [4.8%]). Median rwTTD was 21.4 months (95% confidence interval 17.6, not estimated), and median rwPFS was not reached. The results of the wider cohort will be presented at the meeting, including adverse events. Conclusion: Results from this first interim analysis confirm the efficacy of T-DXd in heavily pretreated patients with HER2+ mBC. Baseline characteristics and demographics are comparable to the clinical trial setting. Analyses are ongoing and will provide more mature rwTTD and rwPFS. XX XX Citation Format: Michelino De Laurentiis, José Ángel García-Sáenz, Giampaolo Bianchini, Cristina Saura, Hans Wildiers, Arthur Allignol, Amanda Logue, Markus Lucerna, Sabine Stamenitis. European real-world experience of patients with HER2+ advanced/metastatic breast cancer accessing trastuzumab deruxtecan through a named patient program: first interim analysis of EUROPA T-DXd [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 PO3-16-12.