SOUTH SAN FRANCISCO, CALIF. For decades oncologists have battled cancer with round after round of chemicals that kill healthy as well as sick cells, and patients have suffered the resultant side effects. Now physicians may have a gentler form of treatment to add to their arsenal, and it shows promise against one of the illnesses women fear most: breast cancer.

Between 25 and 30 percent of malignant breast tumors are especially aggressive because they overproduce a protein, called HER2, that stimulates cells to divide. Researchers at the biotechnology firm Genentech and several university medical centers have been studying a new monoclonal antibody drug, Herceptin, that latches onto HER2 proteins and prevents them from delivering the "divide" message. They gave Herceptin plus standard chemotherapy to 235 women diagnosed with tumors that had spread beyond the breast and lymph nodes. A comparison group of 234 women received only chemotherapy.

Herceptin enhanced the effects of the standard treatment, slowing the cancer's progression by about three months. Almost half of the patients who had both treatments saw their tumors shrink, compared with fewer than one-third of those treated solely with chemotherapy. In a separate study in which Herceptin was used alone, the drug shrank tumors in 16 percent of women whose cancers had returned after chemotherapy.
Herceptin did bring on fever and chills (primarily after the first treatment) in 40 percent of those who took it. When given with chemotherapy drugs known to weaken the heart, it increased the likelihood of such damage. Still, experts say, most patients tolerated the drug well.

"Herceptin is not a cure," says oncologist Mark Pegram of the University of California at Los Angeles. "But it's an important step. For the first time, we're getting at the root of the problem, targeting a protein that may play a critical role in causing cancer."

The Food and Drug Administration is scheduled to decide this fall whether to approve the drug.
Vital Signs by Christie Aschwanden, Susan Freinkel, Rachele Kanigel, and Evelyn Strauss.

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A kinder, gentler, and more effective approach to treating breast cancer is now available. On September 25, the Food and Drug Administration (FDA) approved Herceptin for treating metastatic breast cancer.

Herceptin is a monoclonal antibody, a drug designed to home in on specific cancer cells -- in this case, those that manufacture a protein called HER2. The protein, which is overproduced in 25 -- 30% of breast-cancer cells, transmits a growth signal to the nucleus, or brain center, of the cell. By attaching to HER2, Herceptin blocks the signal, thereby curtailing the growth and proliferation of tumors. Herceptin is recommended only for women whose tumors overexpress HER2. A test to identify such tumors was also approved by the FDA on the same day.

Reports of the drug's effectiveness in treating advanced cancers were released last May at the annual meeting of the American Society of Clinical Oncology. The data indicated that Herceptin, when added to conventional chemotherapy, significantly increased the tumor-response rate, delayed the progression of the disease, and extended the survival period. When used alone, Herceptin shrank tumors by 50% or more in 14% of women with metastatic disease for whom two other forms of chemotherapy had been ineffective.

Although Herceptin did not appear to cause nausea, vomiting, hair loss, or the destruction of immune-system cells -- common side effects of cancer chemotherapy -- it was associated with transient chills and fever, diarrhea, and increased susceptibility to infection. It also appeared to increase the risk of heart problems when used in conjunction with anthracyclines and cyclophosphamide but not with Taxol. As a result, the FDA has approved Herceptin only to be used alone or in combination with Taxol.