SABCS 2024: T-DXd vs Chemotherapy in Previously Treated Metastatic Breast Cancer

By: Vanessa A. Carter, BS
Posted: Thursday, December 12, 2024

Aditya Bardia, MD, MPH, of Harvard Medical School and Massachusetts General Hospital, Boston, and colleagues performed the DESTINY-Breast06 study to evaluate the efficacy and safety of the antibody-drug conjugate fam-trastuzumab deruxtecan-nxki (T-DXd) vs chemotherapy in patients with breast cancer who received prior endocrine-based therapy. Presented during the 2024 San Antonio Breast Cancer Symposium (SABCS; Abstract LB1-04), the results of additional analysis of this clinical trial suggest T-DXd demonstrates clinically meaningful efficacy compared with chemotherapy.

A total of 570 patients with hormone receptor–positive, HER2-low metastatic breast cancer who received at least one prior line of endocrine-based therapy were randomly assigned 1:1 to receive 5.4 mg/kg T-DXd every 3 weeks or physician’s choice of chemotherapy. Individuals with metastatic breast cancer generally had at least two prior therapy lines, or one line if progressive disease occurred while on treatment.

Disease progression occurred in 124 patients within 6 months, in 112 patients within 6 to 12 months, and in 334 patients after 12 months of therapy. T-DXd significantly extended progression-free survival, regardless of when disease progression occurred. Further, the objective response rate among patients treated with T-DXd whose disease progressed within 6 months was significantly higher than for those treated with chemotherapy (67.7% vs 25.4%); individuals with a longer time to disease progression also experienced a benefit with T-DXd.

Patients with investigator-assessed primary and secondary endocrine resistance appeared to demonstrate similar efficacy outcomes. Of note, the median duration of response was numerically improved across the less-than-6-months (11.1 vs 7.3 months), 6-to-12-months (13.7 vs 11.5 months), and more-than-12 months (15.7 vs 11.1 months) disease progression subgroups.

Furthermore, the rate of grade 3 or higher adverse events was also similar across treatment groups and consistent with the overall safety population. Patients in the T-DXd group had a higher incidence of events in each subgroup.

Disclosure: For full disclosures of the study authors, visit sabcs.org.

2024 San Antonio Breast Cancer Symposium

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