Trastuzumab for HER2-positive breast cancer

What the study found

The HER2 gene is amplified and its receptor overexpressed in roughly 25 to 30 percent of breast cancers, which makes the tumor more aggressive. In this randomized trial (New England Journal of Medicine, 2001), women with metastatic breast cancer that overexpressed HER2 were assigned to standard chemotherapy alone (234 patients) or chemotherapy plus trastuzumab (235 patients), a recombinant monoclonal antibody directed against HER2. Adding trastuzumab slowed disease progression and improved response and survival compared with chemotherapy alone.

How it works

Trastuzumab binds the HER2 receptor on the surface of tumor cells that carry it in excess, blocking the growth signaling that drives these cancers and marking the cells for the immune system. Because the target is present at high levels mainly on HER2-positive tumors, the benefit is confined to that subgroup — which is why HER2 testing determines who receives the drug.

Analysis — the pattern

Read alongside other targeted therapies (this is analysis, not a single-study claim): trastuzumab helped establish the biomarker-matched model — test the tumor for a specific molecular feature, then give a drug aimed at it. A recurring caution is cardiac toxicity when the antibody is combined with certain chemotherapies, which shaped how it is given and monitored.

What is still uncertain

This trial studied metastatic disease; later work moved trastuzumab into earlier-stage treatment. Resistance can develop, the best drug combinations and duration are still refined, and cardiac monitoring remains part of care.