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William J. Gradishar, MD, FACP, FASCO


ASCO 2022: Updated Safety Data From DESTINY-Breast03 on T-DXd Versus T-DM1 in Metastatic Breast Cancer

By: Kayci Reyer
Posted: Monday, June 20, 2022

An updated safety analysis of findings from the phase III DESTINY-Breast03 study, presented at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract 1000), suggested that treatment with the antibody-drug conjugate fam-trastuzumab deruxtecan-nxki (T-DXd) may continue to be tolerable during long-term use in patients with HER2-positive metastatic breast cancer. The DESTINY-Breast03 study compared the safety and efficacy of T-DXd and the antibody-drug conjugate ado-trastuzumab emtansine (T-DM1) in this patient population.

“This longer safety update reinforces the consistent safety profile of T-DXd, supporting the clinical benefit of T-DXd over T-DM1 in patients with HER2-positive [metastatic breast cancer],” concluded Erika P. Hamilton, MD, of the Sarah Cannon Research Institute, Nashville, and colleagues.

The study included patients with metastatic and/or unresectable breast cancer who were randomly assigned to receive either T-DXd or T-DM1. At data cutoff in September 2021, treatment was ongoing in 45.1% of patients receiving T-DXd (n = 116) and 14.9% of patients receiving T-DM1 (n = 39). The median treatment duration was 16.1 months for T-DXd versus 6.9 months for T-DM1.

Although adverse events of any grade, ≥ grade 3, or designated as serious occurred at comparable rates in the T-DXd and T-DM1 groups, both serious adverse events and those of ≥ 3 were less common with T-DXd when incidence rates were adjusted for exposure. T-DXd was associated with a longer median time to treatment-emergent adverse events leading to dose reduction (96 days vs. 19 days) or treatment discontinuation (224 vs. 147 days). Among adverse events affecting at least 20% of patients, most were hematologic or gastrointestinal.

Nausea, vomiting, and alopecia were more likely to occur during cycle 1 than in later cycles for those receiving T-DXd. Conversely, hematologic events were less likely to occur in early cycles for either treatment group. In the T-DXd group, adjudicated, treatment-related interstitial lung disease/pneumonitis was more common (10.9% vs. 1.9%) and occurred sooner (5.9 vs. 9.5 months) in the T-DXd group. Most cases in both groups had been resolved by data cutoff.

Disclosures: For full disclosures of the study authors, visit

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