Trastuzumab Rezetecan in ERBB2-Low Advanced Breast Cancer: The HORIZON-Breast06 Randomized Clinical Trial.

Trastuzumab rezetecan significantly prolonged progression-free survival in ERBB2-low advanced breast cancer versus physician’s choice chemotherapy, with median 16.4 vs 6.8 months.

• Why it matters: ERBB2-low metastatic breast cancer has limited effective options early in metastatic treatment, and prior evidence came from a phase 1 setting.
• What they did: In an open-label randomized phase 3 trial at 73 hospitals in China, 551 women with centrally confirmed ERBB2-low disease received trastuzumab rezetecan 6.4 mg/kg every 3 weeks (n=277) or physician’s choice chemotherapy (n=274).
• The result: Progression-free survival improved in chemotherapy-naive patients (16.6 vs 6.8 months; HR 0.25; P<.001) and the overall population (16.4 vs 6.8 months; HR 0.27; P<.001), with grade 3+ treatment-related adverse events in 84.1% vs 67.9%.