Long-term DESTINY-Breast03 results confirm previous findings

MedNet.nl: In women with metastatic HER2-positive breast cancer previously treated with a taxane and trastuzumab, trastuzumab deruxtecan (T-DXd) leads to a clinically significant improvement in overall and progression-free survival compared with trastuzumab emtansine (T-DM1). This is shown in a new analysis of the DESTINY-Breast03. The long-term results further show that the toxicity profile of T-DXd remains manageable. The last update of the phase 3 DESTINY-Breast03 trial showed that after a median follow-up of 28.4 months, there was a significant benefit of T-DXd over T-DM1, with a median progression-free survival (PFS) of 28.8 versus 6.8 months. At the time of this analysis, median overall survival (OS) in the T-DXd arm had not yet been reached. At the ASCO Congress, researchers presented a new analysis with a median follow-up of 43.0 months in the T-DXd group and 35.4 months in the T-DM1 group. This analysis showed that the median OS had now been reached. It was 52.6% in the T-DXd group and 42.7% in the T-DM1 group (HR=0.73). After 36 and 42 months, 67.6% versus 55.7% and 62.5% versus 50.1% of patients were still alive, respectively. PFS results and objective response rates (ORRs) were similar to previous findings. The median PFS in the T-DXd arm and the T-DM1 arm was 29.0 months versus 7.2 months, respectively. After 36 months, 45.7% and 12.4% of patients showed no progression, respectively. The ORR was 78.9% versus 36.9%. Grade 3/4 adverse events occurred in 48.6% of patients in the T-DXd group and in 42.5% in the T-DM1 group. The researchers further noted that most cases of treatment-related interstitial lung disease or pneumonitis occurred in the first year of treatment. As of the last analysis, there were four in the T-DXd arm, all of grade 2. Long-term follow-up of DESTINY-Breast03 supports treatment with T-DXd in patients with HER2-positive metastatic breast cancer previously treated with a taxane and trastuzumab, the researchers said. Hamilton EP, Hurvitz SA, Im SA, et al. Trastuzumab deruxtecan (T-DXd) vs trastuzumab emtansine (T-DM1) in patients (pts) with HER2+ metastatic breast cancer (mBC): Updated survival results of DESTINY-Breast03. ASCO 2024, abstract 1025. Hurvitz SA, Hegg R, Chung WP, et al. Trastuzumab deruxtecan versus trastuzumab emtansine in patients with HER2-positive metastatic breast cancer: updated results from DESTINY-Breast03, a randomized, open-label, phase 3 trial. Lancet 2023;401(10371):105-17. This article was originally published in Dutch on MedNet.nl

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Long-term DESTINY-Breast03 results confirm previous findings

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