Abstract P4-01-36: Real World Data for Trastuzumab Deruxtecan in HER2-Positive Metastatic Breast Cancer Patients with Brain Metastases

Abstract

Abstract Background: Trastuzumab deruxtecan (T-DXd) improves outcomes in HER2-positive metastatic breast cancer (MBC) patients, including patients with previously treated stable brain metastases (BMs). Our objective was to examine the characteristics of HER2-positive MBC patients with BMs prior to T-DXd use. Methods: We performed a retrospective cross-sectional study of T-DXd prior authorization (PA) approvals by OncoHealth for HER2-positive MBC patients between 1/17/2020 – 6/21/2022. Using medical records and utilization management data, we assessed the characteristics of PA approvals for 145 patients requesting T-DXd in Stage 4, HER2-positive, female MBC with BMs. Results: Brain metastases were identified in 41/145 patients with HER2-positive MBC prior to T-DXd authorization. Among the 41 patients The mean age was within the range of 50-59 years, 72% were hormone receptor-positive, and all were HER2 positive. 19/41(46%) had symptomatic BMs, 5/41(12%) had asymptomatic BMs. Prior local therapies for the BMs included craniotomy in 19.5% and brain radiotherapy in 87.8% prior to T-DXd. The median number of prior MBC therapies was 2 (range: 0-8) and 73% (30/41) did not receive tucatinib-based therapy prior to T-DXd. Tucatinib-based therapy was the most common subsequent line of therapy among T-DXd patients with further therapy (5/8). For available data (13 metastatic patients), 8 metastatic patients received tucatinib for an average of 149 days before receiving T-DXd for an average of 238 days, compared to 5 metastatic patients who received T-DXd for an average of 295 days before receiving tucatinib for 240 days, implying improved disease management in the T-DXd-to-tucatinib sequence. Conclusions: In the real world, patients with symptomatic, progressing BMs are more likely to receive T-DXd prior to tucatinib or potential tucatinib-based therapy, with longer duration of stability and treatment. Appropriate sequencing of available treatments with activity on brain metastases such as T-DXd and tucatinib-based therapy needs to be further studied. Citation Format: Andrew Toler, Laura R. Bobolts, Mark Mangurian, Melissa Pozotrigo, Corey Wise, Hiywete Solomon, Nicole Hartung, Rory Makielski, Shika Marur, Meera Ravindranathan, Shanthi Marur. Real World Data for Trastuzumab Deruxtecan in HER2-Positive Metastatic Breast Cancer Patients with Brain Metastases. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-36.