Updated Safety and Efficacy Findings of the Phase 3 DESTINY-Breast03 Study

Erika P. Hamilton, MD, discusses the key safety and efficacy findings from the phase 3 DESTINY-Breast03 study.

Erika P. Hamilton, MD, lead investigator and director of the Breast and Gynecologic Cancer Research Program at the Sarah Cannon Research Institute/Tennessee Oncology, discusses the key safety and efficacy findings from the phase 3 DESTINY-Breast03 study (NCT03529110).

According to the safety update of the study, 54.9% of patients discontinued from receiving treatment trastuzumab deruxtecan-nxki (Enhertu) vs 85.1% who discontinued T-DM1. Between arms, the rates of treatment-emergent adverse events (TEAEs) were similar and any-grade TEAEs were experienced by 99.6% of the trastuzumab deruxtecan arm vs 95.4% in the T-DM1 arm.

TEAEs which were grade 3 or greater were experienced by 53.3% and 49.8% for each arm, and serious TEAEs of any grade were seen in 21.0% of patients in the trastuzumab deruxtecan arm and 19.2% of patients in the T-DM1 arm, respectively. Additionally, grade 3 or greater serious TEAEs were observed in 15.2% and 14.6% of patients for each treatment, respectively.


0:08 | The main efficacy finding with DESTINY-Breast03 was reported previously and showed a 72% reduction in the risk of progression, so really outstanding results compared with T-DM1 which previously was our standard in the second-line setting. Again, what we saw was although things like nausea, vomiting, and hair loss were more common with trastuzumab deruxtecan, overall serious events, or grade 3 or greater events, were very similar between the arms.

0:41 | When we use these exposure adjusted incidence rates to compare how many AEs were happening compared with how long patients could remain on the therapy and continue to get benefit, we saw that, almost across the board, those were lower with trastuzumab deruxtecan than T-DM1.