Antibody-Drug Conjugate Improves Survival in HER2-Low Breast Cancer
A phase III trial in China found that trastuzumab rezetecan, an antibody-drug conjugate, lengthened progression-free survival in HER2-low metastatic breast cancer compared with chemotherapy chosen by physicians. The benefit appeared across hormone-receptor groups, and early overall survival data favored the experimental drug. Editorialists noted that the agent has not been shown superior to trastuzumab deruxtecan, which remains preferred where available.
The HORIZON-Breast06 trial enrolled 551 patients at 73 Chinese hospitals, median age 55; most had no prior chemotherapy for metastatic disease and nearly three-quarters were hormone-receptor positive. Participants received trastuzumab rezetecan or a physician-selected chemotherapy from several standard options.
Progression-free survival was 16.4 months with the ADC versus 6.8 months with chemotherapy overall, with similar gains in chemotherapy-naive and hormone-receptor-positive groups. Twelve-month overall survival was 90.6% versus 81.4%, though mature survival data are pending.
For patients with HER2-low metastatic breast cancer, a new option could matter most where existing ADCs are unavailable or unaffordable, and it may offer another sequence after relapse. Clinicians and health systems may weigh immature survival data, toxicity, and local approval against established trastuzumab deruxtecan. Its societal effect may depend on confirmatory evidence, pricing, and access rather than the trial result alone.