Abstract P2-12-15: Trends in Antiemetic Use in Patients Receiving Fam-trastuzumab Deruxtecan-nxki for Metastatic Breast Cancer: A Retrospective Analysis of Data from the IntegraConnect PrecisionQ De-Identified Database

Abstract Background: Clinical practice guidelines recommend treatment with 3-4 antiemetic drugs for regimens with high emetic risk, such as fam-trastuzumab deruxtecan-nxki (T-DXd). This study uses real-world data to characterize the real-world use of antiemetics in patients with metastatic breast cancer (mBC) and explores the impact of antiemetic treatment on T-DXd outcomes. Methods: This was a retrospective, observational analysis of data from patients in the IntegraConnect PrecisionQ real-world de-identified database, enriched with information obtained by curation. The study included adults (age ≥18 years) with a confirmed diagnosis of mBC who initiated treatment with T-DXd between December 20, 2019 and December 31, 2023. The index date was the date of T-DXd initiation and follow-up was through May 20, 2024. Antiemetic classes were defined using data obtained within the first 7 days of T-DXd initiation using National Comprehensive Cancer Network (NCCN) criteria. Outcomes included time to treatment discontinuation (TTD), the rate of dose reductions for T-DXd, and the rate of antiemetic use over time in patients receiving T-DXd. Also included were demographics and clinical characteristics. Data are presented using descriptive statistics. Results: Overall, 2,132 patients were included in the analyses, most were female (98.4%) and white (62.2%). The median (interquartile range [IQR]) age at diagnosis was 59 (50, 67) years and the median (IQR) age at treatment was 63 (54, 71) years. Most patients (82.4%) had an Eastern Cooperative Oncology Group (ECOG) score of 0-1; 13.9% were ECOG 2 and 3.7% were ECOG 3+. A total of 113 patients received no antiemetics, 136 received 1 antiemetic class, 1090 received 2 antiemetic classes, and 793 received 3-4 antiemetic classes. Over a median follow-up duration (IQR) of 16.3 (11.0, 28.0) months, 11.0 (5.7, 21.0) months, 13.8 (7.0, 19.7) months, and 9.1 (5.9, 13.8) months for each group, respectively, the number of patients who discontinued/died was 96 (85.0%), 94 (69.1%), 745 (68.3%), and 433 (54.6), respectively. The median (95% confidence interval [CI]) TTD was 7.0 (5.6, 8.3) months, 7.6 (5.5, 12.4) months, 8.3 (7.6, 9.2) months, and 9.0 (8.0, 9.6) months for patients treated with 0, 1, 2, and 3-4 antiemetic classes, respectively. At 6 months, treatment probability (95% CI) was 58.6% (48.8, 67.1), 55.2% (46, 63.4), 59.6% (56.5, 62.5), and 61.5% (57.9, 64.8), respectively; and at 18 months it was 15.4% (9.1, 23.3), 22% (13.8, 31.6), 26.1% (23.2, 29.2), and 30.2% (25.4, 35.2), respectively. The number of patients receiving 3-4 antiemetics has been increasing since the end of 2021, and in 2023, more patients were receiving 3-4 antiemetic classes (n=574) than 2 antiemetic classes (n=294). In an analysis of patients who were on T-DXd for ≥6 months (n=1027), the rate of dose reduction decreased with the number of antiemetic classes (32.7% for 0-1 classes, 27.5% for 2 classes, 24.9% for 3+ classes). Conclusion: In this analysis of real-world data, persistence on T-DXd treatment increased with the number of antiemetic classes administered. Following the NCCN guideline update, patients receiving T-DXd are now treated with 3 or more antiemetic classes. The requirement for dose reduction appears to be reduced when more antiemetic classes are used. Citation Format: Stephan Rosenfeld, Vikram Gorantla, Rushir Choski, Debra Patt, Anupama Vasudevan, Anna Rui, Dawn Brenneman, Mike Gart, Prateesh Varughese, Brandon Wang, Lisa Morere,Simon Blanc. Trends in Antiemetic Use in Patients Receiving Fam-trastuzumab Deruxtecan-nxki for Metastatic Breast Cancer: A Retrospective Analysis of Data from the IntegraConnect PrecisionQ De-Identified Database [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P2-12-15.