The document summarizes information about a new cancer drug called Herceptin. It discusses how Herceptin was tested in 3 large clinical trials involving women with breast cancer. The results showed that women who received Herceptin along with chemotherapy had their risk of cancer recurrence halved compared to chemotherapy alone. Herceptin is currently licensed to treat advanced breast cancer but not early breast cancer, and longer-term follow up is still needed to fully understand its effectiveness.