Human epidermal growth factor receptor 2 (HER2) is a key marker for breast cancer and HER2-targeted therapy has improved the prognosis for patients with HER2 overexpressed breast cancer. HER2 positivity is defined as HER2 protein overexpression measured by immunohistochemistry (IHC) or HER2 gene amplification evaluated by in situ hybridization (ISH). As the protein expression of HER2 IHC 3+ is higher than that of HER2 IHC 2+, we suppose patients with HER2 IHC 3+ tumor would have better response to anti-HER2 therapy, and their prognosis would better than that of HER2 IHC 2+ tumor. This study aimed to evaluate whether the degree of HER2 IHC positivity affected the outcome of early breast cancer.
Clinicopathological information of 785 consecutive cases of HER2+ early breast cancer who underwent surgery at Taipei Veterans General Hospital, Taiwan, ROC from 2007 October to 2015 December were retrieved from the medical records. Survival curves were plotted by Kaplan-Meier method, and their differences were calculated by log-rank test. Cox regression model was used to evaluate the hazard of recurrence and death, and the influences of the age of patients, stage, hormonal receptor status, anti-HER2 treatment were adjusted.
Recurrence-free survival of cases with HER2 IHC 3+ tumor was significantly better than that of cases with HER2 IHC 2+ tumor (p = 0.018). Multivariate Cox regression revealed the hazard ratios of cases with HER2 IHC 3+ was significant smaller than those with HER2 IHC 2+ in both RFS (p = 0.001) and OS (p = 0.007).
We confirmed that the intensity of HER2 IHC provided prognostic information for HER2 positive breast cancer. The prognosis of HER2 IHC 3+ cases was significantly better than that of HER2 IHC 2+ and ISH amplified cases. Accurate HER2 testing is important to maximize the benefit of anti-HER2 therapy.
Clinical trial identification
Legal entity responsible for the study
Has not received any funding.
All authors have declared no conflicts of interest.