Abstract GS2-01: GS2-01 Trastuzumab deruxtecan vs physician’s choice in patients with HER2+ unresectable and/or metastatic breast cancer previously treated with trastuzumab emtansine: primary results of the randomized, phase 3 study DESTINY-Breast02

Abstract

In DESTINY-Breast01 (NCT03248492) and DESTINY-Breast03 (NCT03529110), trastuzumab deruxtecan (T-DXd) demonstrated unprecedented activity in patients (pts) with HER2+ (immunohistochemistry 3+; immunohistochemistry 2+/in situ hybridization+) advanced metastatic breast cancer (mBC), leading to regulatory approvals in several countries for HER2+ unresectable/mBC after a prior anti–HER2-based regimen. DESTINY-Breast02 (NCT03523585) is a phase 3 trial of T-DXd vs treatment of physician’s choice (TPC) in patients with centrally confirmed HER2+ mBC previously treated with trastuzumab emtansine (T-DM1). It acts as a confirmatory study for the pivotal phase 2 DESTINY-Breast01 trial. Here we report the primary results of DESTINY-Breast02. Methods: Pts with HER2+ mBC were randomized 2:1 to receive T-DXd or TPC (trastuzumab + capecitabine or lapatinib + capecitabine) and stratified by hormone receptor (HR) status (HR+/HR-), prior pertuzumab treatment, and history of visceral disease. The primary endpoint of this time-driven primary analysis was progression-free survival (PFS) as determined by blinded independent central review (BICR). The powered secondary endpoint was overall survival (OS). Other secondary endpoints included confirmed objective response rate (ORR) by BICR, duration of response (DoR) by BICR, PFS by investigator assessment, safety, and others. Results: 608 pts were randomized to receive T-DXd (n = 406) or TPC (n = 202). Pts receiving T-DXd and TPC had a median age of 54.2 years (range, 22.4-88.5 years) and 54.7 years (range, 24.7-86.5 years), respectively, with a median of 2 (range, 0-10 and range,1-8) prior lines of systemic therapy (excluding hormone therapy) in the metastatic setting. Median treatment duration was 11.3 mo in the T-DXd arm and ~4.5 mo in the TPC arm. Efficacy and safety results are shown in the table below. T-DXd significantly improved PFS (HR, 0.36; 95% CI, 0.28-0.45; P <0.000001) and OS (HR, 0.66; 95% CI, 0.50-0.86; P = 0.0021) compared with TPC. Confirmed ORR was 69.7% (14% complete response) with T-DXd and 29.2% (5.0% complete response) with TPC. Grade ≥3 treatment-emergent adverse events (TEAEs) occurred in 52.7% and 44.1% of pts receiving T-DXd and TPC, respectively. Adjudicated drug-related interstitial lung disease (ILD) occurred in 10.4% of pts with T-DXd vs 0.5% of pts with TPC. In pts receiving T-DXd, most ILD cases (88.1%) were grade 1/2 and grade 5 ILD was reported in 2 (0.5%) pts. Conclusions: Results from DESTINY-Breast02 confirmed the clinical benefit and superiority of T-DXd over conventional chemotherapy-based regimens in pts with HER2+ mBC previously treated with T-DM1, as evidenced by significant and clinically meaningful improvements in PFS and OS. These data, together with earlier reported results from the DESTINY-Breast03 study of T-DXd vs T-DM1 solidify T-DXd as an optimal treatment option in pts with progressive HER2+ mBC across broad settings. Editorial Acknowledgment Under guidance of the authors, assistance in medical writing and editorial support was provided by Caylin Bosch, PhD, of ApotheCom, and was funded by Daiichi Sankyo. Funding This study was funded by Daiichi Sankyo and AstraZeneca. Table. Summary of Efficacy and Safety Results for T-DXd and TPC in Patients With HER2+ mBC Previously Treated With T-DM1 Citation Format: Ian Krop, Yeon H. Park, Sung-Bae Kim, Giuliano Borges, Sercan Aksoy, Joaquin Gavila Gregori, Rebecca Roylance, Elgene Lim, Rinat Yerushalmi, Flora Zagouri, Francois P. Duhoux, Tanja Fehm, Toshimi Takano, Anton Egorov, Iris Wu, Jillian Cathcart, Changan Chu, Fabrice Andre. GS2-01 Trastuzumab deruxtecan vs physician’s choice in patients with HER2+ unresectable and/or metastatic breast cancer previously treated with trastuzumab emtansine: primary results of the randomized, phase 3 study DESTINY-Breast02 [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 GS2-01.

Update Breast Cancer 2023 Part 2 – Advanced-Stage Breast Cancer

“…This corresponded to a hazard ratio of 0.36 (95% CI: 0.28–0.45). There was no difference in efficacy in patients with (HR = 0.35; 95% CI: 0.20–0.61) and without brain metastases (HR = 0.38; 95% CI: 0.29–0.48) 33 .…”

“…The median overall survival in the T-DXd arm was 39.2 months (95% CI: 32.7–NE) and 26.5 months (95% CI: 21.0–NE). This corresponded to a hazard ratio of 0.66 (95% CI: 0.50–0.86) in favor of T-DXd 33 .…”

“…The Destiny-Breast 02 study was conducted in parallel with the Destiny-Breast 03 study 33 . However, this study included patients who had already completed treatment with T-DM1.…”

“…Most patients were treated as part of the study in the third (45%) or fourth line of therapy (30%). The important subgroup of patients with brain metastases consisted of 18.2% in the T-DXd arm and 17.8% in the TPC arm 33 .…”

New Systemic Therapy Strategies for HER2-Positive Metastatic Breast Carcinoma

“…These results were confirmed in the phase III DESTINY-Breast02 study. After previous progression under T-DM1, the median PFS in the T-DXd arm was 17.8 months compared to 6.9 months for treatment of the physician's choice; the median OS was 39.2 months vs. 26.5 months [53].…”