'These trials are significant because we may be able to treat HER2-positive patients in the earlier stages of their breast cancer, and prevent or delay development of metastatic disease.'

After four years in the study, 15 percent of women treated with Herceptin plus chemotherapy experienced disease recurrence, compared to 33 percent of women treated with chemotherapy alone. Preliminary survival data showed a 49 percent improvement in overall survival (or a hazard ratio of 0.67, which is equivalent to a 33 percent reduction in the risk of death). Survival data continue to mature.

Importance of HER2 Test Underscored

"The reduction in disease recurrence observed in these trials was the largest improvement I've seen in breast-cancer clinical research. Herceptin plus chemotherapy can potentially stop or delay early stage HER2-positive breast cancer from relapsing," said Edith Perez, M.D., professor of medicine at the Mayo Clinic in Jacksonville, Fla., and the lead investigator in one of the two Herceptin trials.

"These trials also underscore the importance for every woman diagnosed with breast cancer to receive a HER2 test," Dr. Perez added.

A preliminary safety analysis showed that adverse events in these studies were consistent with those seen in previous Herceptin clinical trials. Each study had an independent external Data Monitoring Committee (DMC) that reviewed data from the studies, including cardiac safety data, on a regular basis.

According to the investigators, serious or life-threatening (and, in rare cases, fatal) cardiac events -- most commonly congestive heart failure (weakening of the heart muscle) -- occurred approximately 3 to 4 percent more often in the Herceptin-plus-chemotherapy arms than in the chemotherapy-alone arms. Patients in these studies will continue to be followed for any additional side effects.

Outcomes Measured in Years, Not Months

In these studies, women with early stage (or cancer that has not spread beyond the breast and the associated lymph nodes) HER2-positive breast cancer received Herceptin plus chemotherapy or chemotherapy alone following initial treatment with surgery and anthracycline and cyclophosphamide (AC). HER2- positive breast cancer is an especially aggressive form of the disease that affects approximately 25 percent of women with breast cancer.

These data were featured in a press briefing at the 41st Annual Meeting of the American Society of Clinical Oncology (ASCO). More detailed data from the study will be presented to meeting attendees by Edward Romond, M.D., of the University of Kentucky during a scientific symposium ("Advances in Monoclonal Antibodies for Breast Cancer" -- Monday, May 16, 1:15 p.m. EDT).

"These trials are significant because we may be able to treat HER2-positive patients in the earlier stages of their breast cancer, and prevent or delay development of metastatic disease," said Susan Desmond-Hellmann, M.D., M.P.H., Genentech's president, product development.

"We're also excited about the improvements seen in the adjuvant setting, since patient outcomes are measured in years rather than months," Dr. Desmond-Hellmann noted.