According to research published early online in the Journal of Clinical Oncology, women with breast cancer with HER2-positive disease who received trastuzumab had improved prognosis compared with women with HER2-negative disease.

Researchers sought to determine whether trastuzumab improves prognosis of women with metastatic human epidermal growth factor receptor 2 (HER2)–positive breast cancer beyond that of women with HER2-negative disease.

A total of 2,091 women with metastatic breast cancer diagnosed between 1991 to 2007 and with known HER2 status and who had not received trastuzumab in the adjuvant setting, were identified. Disease was classified into the following three groups:

• HER2-negative (n=1,782),
• HER2-positive without first-line trastuzumab treatment (n=118), and
• HER2-positive with first-line trastuzumab treatment (n=191)

Overall survival (OS) was estimated using the Kaplan-Meier product-limit method and compared between groups with the log-rank test. Cox proportional hazards models were used to determine associations between OS and HER2 status after controlling for patient characteristics. Median-follow-up was 16.9 months.

The following results were reported:
• One-year survival rates among patients with HER2 -negative disease, HER-positive disease and trastuzumab treatment, and HER2-positive disease and no trastuzumab treatment were 75.1% (95% CI, 72.9% to 77.2%), 86.6% (80.8% to 90.8%), and 70.2% (60.3% to 78.1%), respectively.
• Women with HER2 -positive disease who received trastuzumab had a 44% reduction in the risk of death compared with women with HER2-negative disease (hazard ratio [HR] = 0.56; 95% CI, 0.45 to 0.69; P < 0.0001). This HR varied with time and was statistically significant for the first 24 months, and not after 24 months.

The researchers concluded that women with HER2-positive disease who received trastuzumab had improved prognosis compared with women with HER2-negative disease.