The drug, Herceptin, is already used for advanced cancer. But in three studies involving thousands of women with early-stage disease, it cut the risk of a relapse in half.
"I feel happy for our patients. Happy because we have demonstrated that things are better," the Mayo Clinic's Dr. Edith Perez, a co-author of one of the studies, told The Early Show. "We don't have to wait 10 more years for data. The data is here today, and we're going to apply the information to patients today. So I'm happy. I'm also humble to be a part of this great study."
Several experts used words like "revolutionary," "stunning" and "jaw-dropping" to describe the findings.
"In 1991, I didn't know that we would cure breast cancer and, in 2005, I'm convinced we have," said Dr. Jo Anne Zujewski, head of breast cancer therapeutics at the government's National Cancer Institute.
Herceptin, known generically as trastuzumab, does not help everyone. For one thing, it is only for the estimated 20 percent of breast cancer cases in which tumors churn out too much of a protein known as HER2. In the recent studies, the drug was used along with standard treatments, including surgery and chemotherapy.
"This drug is not a chemotherapy drug. It's not a hormone drug. It's a type of special protein that attacks a protein in the tumor cell. It's very, very specific," Perez said. "If 50,000 women are diagnosed with this disease today or this year in the United States, a thousand will be alive in three years that would not have been alive had this drug not been used. So it could be a cure for these women."
Herceptin could be the biggest thing in cancer drugs since research a decade ago demonstrated the extraordinary effectiveness of tamoxifen, another medicine that transformed the treatment of the disease by homing in on cancer cells but sparing healthy ones.
Herceptin, made by Genentech, appears to have "changed one of the most worrisome kinds of cancers into one that may have a relatively good prognosis," said Dr. Ed Romond of the University of Kentucky.
He was one of the researchers who reported findings from three Herceptin studies Thursday in The New England Journal of Medicine. One was an international study sponsored by Herceptin's European marketer, Roche. The others were North American studies sponsored by the National Cancer Institute. The researchers followed more than 6,500 women with early-stage breast cancer.
In the first study, 220 women taking standard therapy for a year either developed breast cancer again, showed other kinds of tumors, or died. Only 127 did when Herceptin was added.
The two other studies, partly funded by Genentech, reached similar findings in their combined results. At three years, patients on Herceptin showed a disease-free survival rate that was 12 percentage points higher than without it.
The government approved the drug in 1998 for advanced breast cancer that has already spread within the body. But early-stage cases are much more common.