On Apr. 27, 2005, results from two large National Cancer Institute sponsored randomized clinical trials showed that patients with early-stage, HER2-positive, invasive breast cancer who received the monoclonal antibody trastuzumab (Herceptin) in combination with chemotherapy experienced a significant decrease in their risk of cancer recurrence in comparison with patients who received the same chemotherapy without trastuzumab. Trastuzumab slows or stops the growth of these cells, and it is only used to treat cancers that overexpress the HER–2 protein. Approximately 20 percent to 30 percent of breast cancers overexpress HER-2. These tumors tend to grow faster and are generally more likely to recur than tumors that do not overproduce HER-2.

The clinical trials were sponsored by the National Cancer Institute (NCI), part of the National Institutes of Health, and conducted by a network of researchers led by the National Surgical Adjuvant Breast and Bowel Project (NSABP) and the North Central Cancer Treatment Group (NCCTG), in collaboration with the Cancer and Leukemia Group B, the Eastern Cooperative Oncology Group, and the Southwest Oncology Group. Genentech, Inc., South San Francisco, Calif., which manufactures trastuzumab, provided the drug for the trials under the Cooperative Research and Development Agreement (CRADA) with NCI for the clinical development of trastuzumab.

The Data Monitoring Committees overseeing the combined analysis of these trials (known as NSABP-B-31 and NCCTG-N9831)* recommended that the results of a recent combined interim analysis be made public because the studies had met their primary endpoints of increasing disease-free survival (the amount of time patients live without return of the cancer) in patients receiving trastuzumab in combination with chemotherapy. The improvement in overall survival also was statistically significant for women receiving a combination of chemotherapy and trastuzumab.

Patients in the clinical trials who received trastuzumab in combination with standard combination chemotherapy had a 52 percent decrease in disease recurrence compared to patients treated with chemotherapy alone. This difference is highly statistically significant. “This is a major advance for many thousands of women with breast cancer,” said NCI Director Andrew C. von Eschenbach, M.D. “These results are one more example that we are at a major turning point in the use of targeted therapies to eliminate suffering and death from cancer,” he added.

The leaders of the studies underscored the significance of these results and cited the collaborative efforts involved. “These findings confirm that we now have a very potent weapon against the recurrence of cancer cells that overexpress HER-2,” said Edith A. Perez, M.D., who chaired the NCCTG trial and is a medical oncologist at the Mayo Clinic in Jacksonville, Fla. “We gratefully acknowledge the contribution of our co-investigators and, most importantly, our courageous patients in helping to achieve these unprecedented results.”