Data Presented by Dr. Lee Schwartzberg from Renown Cancer Center at the 2022 ASCO Direct Las Vegas Conference.
DESTINY-Breast04, or DB04, was one of the most important and practice-changing trials to be presented at ASCO 2022. DB04 enrolled patients who had unresectable or metastatic breast cancer that was considered resistant to endocrine treatment, and who had received 1 or 2 prior lines of chemotherapy treatment. Importantly, these patients had disease that was considered “HER2-low”, a new classification of breast cancer as defined by specific findings on standard pathology testing. The trial was designed to determine whether treatment with trastuzumab-deruxtecan, or T-DXd, was superior to using the physician’s choice of chemotherapy in HER2-low metastatic breast cancer patients. The trial enrolled 540 patients, the vast majority of whom had hormone receptor-positive, or HR+, disease. The results of DB04 were positive, showing that the patients who were treated with T-DXd survived almost twice as long without a progression of their cancer compared to those treated with treatment of physician’s choice. These results were similar for the hormone receptor-negative patients, who represented a much smaller percentage of the entire study population. Patients on T-DXd in DB04 also lived more than 6 months longer as compared to those treated with chemotherapy of physician’s choice. In addition, about three-times as many patients in the T-DXd group (52%) responded to the treatment with shrinkage of their tumors as compared to those on chemotherapy(16%). Important toxicities of T-DXd observed in DB04 included interstitial lung disease (ILD) and pneumonitis; in most cases, these events were not severe, but some deaths did occur as a result. Although infrequent, some cardiac toxicities, including left ventricular dysfunction and cardiac failure, also occurred in the trial, in accordance with previous results for this type of therapy. The results of DB04 clearly establish T-DXd as a new and preferred treatment option for patients with HER2 low breast cancer, which is estimated to represent approximately half of all patients with metastatic disease.
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