A drug that targets a specific type of breast cancer is about to dramatically change the way doctors treat breast cancer, according to two major new studies.
The combined results show that the drug Herceptin cuts the risk of breast cancer recurrence in half among women with tumors that are HER2-positive. HER2-positive tumors produce more HER2 protein, which is linked with more aggressive forms of the disease and a higher risk of breast cancer death.
Herceptin is a drug designed to block the activity of the HER2 protein.
"A million women each year are diagnosed with breast cancer throughout the world, and approximately 25 percent of them have HER2 tumors," says researcher Edith Perez, MD, of the Mayo Clinic in Jacksonville, Fla., in a news release. "To be able to find a treatment that impacts the lives of so many is a huge success for the cancer research community."
In an editorial that accompanies the studies, published in The New England Journal of Medicine, Gabriel Hortobagyi, MD, of the University of Texas M.D. Anderson Cancer Center, says the findings are “revolutionary.”
The development of breast cancer drugs that target different types of breast cancer “will completely alter our approach to the treatment of breast cancer,” writes Hortobagyi.
New Approach in Breast Cancer Treatment
The first international clinical trial of Herceptin involved more than 5,000 women with HER2-positive breast cancer who had already undergone standard chemotherapy with or without radiation. They were randomly assigned to three groups to receive one or two years of additional treatment with Herceptin (given once every three weeks) or no additional Herceptin treatment.
The complete results, including the women treated for two years with Herceptin, are not yet available. But preliminary results in women treated for one year with Herceptin show the drug reduced the risk of cancer recurrence by 50 percent and prompted the researchers to release the data early.
"This is probably the biggest evidence of a treatment effect I've ever seen in oncology," says researcher Richard Gelber, PhD, of Dana-Farber Cancer Institute, in a news release. "The differences showed up so quickly that the Data Monitoring Committee felt that data had to be released, even though we don't know the long-term effects and the long-term side effects."
The study showed that 220 breast cancer recurrences occurred in the group that did not receive Herceptin, compared with 127 recurrences among the group who took the drug for one year.
Although death rates did not differ significantly between the groups, a second study published in the same journal suggests that Herceptin may also provide a survival advantage.
In the second study, researchers analyzed the results of two different trials of Herceptin in more than 3,000 women with HER2-positive breast cancer. About half of the women received Herceptin in addition to standard chemotherapy for one year after surgical breast cancer treatment.
The results showed a 33 percent reduction in risk of death and about a 50 percent reduction in the rate of cancer recurrence among women treated with Herceptin.
After three years of follow-up, 87.1 percent of women treated with Herceptin were alive and disease-free compared with 75.4 percent of those who did not receive the drug. In addition, there were 62 deaths and 96 women with distant spread of the cancer reported among women treated with Herceptin; that compared with 92 deaths and 193 reports of distant-cancer recurrence in the group that did not receive the drug.
Researchers say there was also a reduction in the incidence of new second cancers (nonbreast) among women treated with Herceptin.
In a perspective that accompanies the studies, Harold Burstein, MD, PhD, of the Dana-Farber Cancer Institute, says the results offer "a profound lesson: not all breast cancers are the same."
Burstein says the success of Herceptin shows that tailoring breast cancer treatment to the specific type of breast cancer “establishes a new standard of treatment for breast cancer.”
By Jennifer Warner, reviewed by Louise Chang, MD
SOURCES: Piccard-Gebhart, M. The New England Journal of Medicine, Oct. 20, 2005; vol 353: pp 1659-1682; Romond, E. The New England Journal of Medicine, Oct. 20, 2005; vol 353: pp 1673-1684. News release, Dana-Farber Cancer Institute. News release, Mayo Clinic.