Trastuzumab after Chemotherapy Is Effective in HER2-Positive Breast Cancer

Treatment with trastuzumab (Herceptin®) for 1 year following standard chemotherapy improved disease-free survival in women with HER2-positive early breast cancer. The finding comes from the third analysis of the Herceptin Adjuvant (HERA) trial, a large multicenter study that compared outcomes in patients randomly assigned to receive standard chemotherapy followed by trastuzumab with those in patients randomly assigned to receive chemotherapy alone (the observation group). The 4-year follow-up results were reported February 25, 2011, in Lancet Oncology.

Luca Gianni, M.D., of the San Raffaele Institute in Milan, Italy, and his colleagues randomly assigned 1,703 women to receive 1 year of adjuvant therapy with trastuzumab and 1,698 women to the observation group. (A third group, not included in this analysis, received 2 years of trastuzumab.) After a median follow-up of 4 years, 79 percent of women in the trastuzumab group were disease free, compared with 72 percent in the observation group. Patients in the trastuzumab group had a roughly 24 percent lower risk of disease [than those in the observation group], and the difference between groups was highly statistically significant. 

Trastuzumab is a monoclonal antibody that targets tumor cells that overproduce a protein called HER2 and interferes with their growth. HER2-positive cancers, which make up about 20 percent of all breast cancers, are more aggressive and women with this form of breast cancer have a higher risk of disease recurrence and death. Trastuzumab extends survival of women with HER2-overexpressing metastatic breast cancer, and the HERA trial is one of several trials that were initiated to determine whether this treatment would benefit patients with early-stage disease as well.

Unlike results from an earlier analysis of the HERA trial, the 4-year follow-up results do not show a statistically significant difference in overall survival between the two groups. “These results are probably heavily influenced by the 52 percent of patients who crossed over from the observation group to the trastuzumab group,” noted Heikki Joensuu, M.D., Ph.D., of Helsinki University Central Hospital in an accompanying editorial. Patients in the observation group who were disease free and did not have heart problems (a possible side effect of trastuzumab) were given the option of crossing over to receive trastuzumab because initial results of the HERA trial had shown a clear benefit in terms of reducing recurrence risk with 1 year of trastuzumab.

The latest analysis “provides further assurance” that giving trastuzumab after standard chemotherapy is effective for treatment of early HER2-positive breast cancer and that such treatment “continues to show a generally favorable safety profile with a low rate of congestive heart failure,” Dr. Joensuu wrote. Questions still remain about whether it’s best to give trastuzumab with chemotherapy or after chemotherapy (the risk for heart complications increases when trastuzumab is combined with some chemotherapy drugs), and how long to treat with trastuzumab, he noted.