Purpose: Human epidermal growth factor receptor 2 gene (HER2) is associated with a poorer outcome in node-positive breast cancer, but the results are conflicting in node-negative disease. This study assessed the prognostic impact of HER2 overexpression/amplification in a large series of node-negative breast cancers.
Patients and methods: A tissue microarray (TMA) series was constructed consisting of 4,444 invasive breast cancers diagnosed in British Columbia from 1986 to 1992. Within this series, 2,026 patients were node negative, of whom 70% did not receive adjuvant systemic therapy. The TMA series was assessed for estrogen receptor (ER) and HER2. Logistic regression modeling was used to estimate odds ratios at the 10-year follow-up.
Results: HER2 was positive in 10.2% of the node-negative cohort. In this cohort, an inferior outcome was seen in patients with HER2-positive tumors compared with HER2-negative tumors for 10-year relapse-free survival (RFS; 65.9% v 75.5%, respectively; P = .01), distant RFS (71.2% v 81.8%, respectively; P = .004), and breast cancer-specific survival (BCSS; 75.5% v 86.3%, respectively; P = .001). A trend for a worse overall survival was also seen (P = .06). HER2 was an independent poor prognostic factor for RFS and BCSS at 10 years, with odds ratios of 1.71 (P = .01) and 2.03 (P = .003), respectively. The number of HER2-positive tumors that were <or= 1 cm was small, but there was a trend for a worse outcome in T1b tumors.
Conclusion: HER2 overexpression/amplification is correlated with a poorer outcome in node-negative breast cancer. Larger studies are needed to more clearly define the prognostic impact of HER2 in tumors <or= 1 cm, particularly within the separate hormone receptor subgroups.