Trastuzumab deruxtecan in HER2-low metastatic breast cancer: long-term survival analysis of the randomized, phase 3 DESTINY-Breast04 trial

In DESTINY-Breast04 ( NCT03734029 ), trastuzumab deruxtecan (T-DXd) significantly improved overall survival (OS) and progression-free survival compared with treatment of physician’s choice of chemotherapy (TPC) for patients with human epidermal growth factor receptor 2-low (HER2-low) (immunohistochemistry (IHC) 1+ or IHC 2+/in situ hybridization-negative) metastatic breast cancer. After an extended median follow-up of 32.0 months, median OS in the overall cohort was 22.9 months for T-DXd and 16.8 months for TPC (hazard ratio 0.69; 95% confidence interval 0.55–0.86). For the hormone receptor-positive cohort, median OS was 23.9 and 17.6 months for T-DXd and TPC, respectively (hazard ratio 0.69; 95% confidence interval 0.55–0.87). Median OS also favored T-DXd in exploratory analyses of hormone receptor-negative, estrogen receptor IHC 1%–10% and estrogen receptor IHC >10% cohorts. The overall safety profile of T-DXd was acceptable and generally manageable. Results confirm T-DXd as standard of care after prior chemotherapy in patients with HER2-low metastatic breast cancer. ClinicalTrials.gov identifier: NCT03734029 . This prespecified updated survival and exploratory subgroup efficacy analysis of the phase 3 DESTINY-Breast04 trial shows that trastuzumab deruxtecan treatment in patients with HER2-low metastatic breast cancer leads to continuous survival benefit irrespective of estrogen receptor or hormone receptor status.