Learning you have breast cancer is bad enough, but the diagnosis is doubly devastating for the 20 to 30 percent of patients who turn out to be "HER-2-positive." Tumors carrying that designation grow with unusual speed, and are more likely to recur after treatment. "Hearing you have HER-2," says Darlene Nipper, 40, "is like hearing a death sentence."

Not anymore. Last week researchers confirmed that Herceptin--a drug previously reserved for metastatic breast cancer--can help keep high-risk patients from reaching that desperate stage. In two clinical trials involving 3,300 newly diagnosed HER-2-positive patients, those who got Herceptin along with conventional chemotherapy suffered only half the recurrence rate of patients on chemo alone. The Herceptin patients were also more likely to be alive and disease-free four years later. "We don't like to overstate things, but the results are stunning," says Dr. JoAnne Zujewski of the National Cancer Institute, which sponsored the trials.

Herceptin, known generically as trastuzumab, is one of several new cancer treatments designed to home in directly on tumor cells. The drug molecule--a so-called monoclonal antibody--latches onto HER-2 receptors on the cells, cutting them off from the chemical signals they need to maintain themselves. The antibody also marks cancer cells for destruction by the immune system. Yet it has minimal impact on normal, healthy cells, so the side effects are relatively mild: fever and chills during the first infusion, along with mild headaches and nausea.

The new therapy isn't perfect. Some women don't respond to it, and the new studies found that congestive heart failure was 3 to 4 percent more common in Herceptin patients than in those receiving chemotherapy alone. Still, "every woman like me should have access to this drug," says Nipper, a trial participant whose cancer is now in remission. "You shouldn't have to wait until the disease gets out of control." As FDA regulators review the new findings, they're likely to agree.