Update of DESTINY-Breast03 Emphasizes Safety of Trastuzumab Deruxtecan in mBC

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 updated safety analysis of the DESTINY-Breast03 trial (NCT03529110) and the patients who were enrolled in the study.

Hamilton presented findings of the DESTINY-Breast03 trial at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting. During her session, she compared the safety of trastuzumab deruxtecan (Enhertu) with trastuzumab emtansine (TDM-1) for patients with HER2-positive unresectable or metastatic breast cancer.

In the trial, patients were randomized in a 1:1 ratio to receive either trastuzumab deruxtecan (n = 257) or trastuzumab emtansine (n = 261). While the efficacy data from the study was from a primary data cutoff of May 21, 2021, the updated safety findings were from a cutoff of September 7, 2021.

Transcription:

0:08 | This was the safety update for DESTINY-Breast03. As you recall, trastuzumab deruxtecan was initially approved based on DESTINY-Breast01 [NCT03248492]. DESTINY-Breast03 was a study that brought it up into an earlier-line setting, so patients that had seen trastuzumab and/or a taxane in the metastatic setting or relapsed within 6 months of neoadjuvant or adjuvant therapy. Based on DESTINY-Breast03, trastuzumab deruxtecan got a new expanded indication in earlier-line settings in May 2022.

0:42 | As opposed to the plenary [session], where DESTINY-Breast04 [NCT03734029] looked at patients who had HER2-low expression [and unresectable and/or metastatic breast cancer], this was a study of that 15% to 20% of patients with breast cancer who we know have too high [expression]. That's 3+ by immunohistochemistry, or fluorescence in situ hybridization–positive.

1:01 | This study, opposed to DESTINY-Breast01 that was with very heavily pretreated patients, looked at patients in the so-called second-line setting. They had seen trastuzumab and a taxane in the metastatic setting or relapsed within 6 months of receiving HER2 directed therapy in the neoadjuvant or adjuvant setting.