Pathologic complete response to neoadjuvant therapy predicts prognosis in HER2-positive breast cancer

This study assessed the impact of pathologic complete response (pCR) to neoadjuvant chemotherapy and trastuzumab (herceptin) on survival of HER2-positive breast cancer patients.

Neoadjuvant therapy refers to treatments given before surgery in order to shrink the tumor and allow for complete surgical removal of the cancer. Neoadjuvant therapies often allow patients to receive breast conserving surgery (removal of the tumor alone without removing the entire breast). Common neoadjuvant therapies include chemotherapy agents such as anthracycline and taxane based drugs. Trastuzumab is another effective neoadjuvant treatment for HER2-positive breast cancers. Trastuzumab binds to HER2 (Human epidermal growth factor receptor 2; a protein found on the surface of some breast cancer cells that promotes tumor growth), preventing it from fuelling cancer progression.

The goal of neoadjuvant therapy is to achieve pathologic complete response (pCR). pCR is defined as the absence of any residual tumor cells when surgery is eventually performed (the tissue removed by surgery is examined under a microscope to determine the response to neoadjuvant therapy). This study investigated the value of pCR in predicting patient survival.

A total of 229 patients with HER2-positive breast cancer were followed during this study. All patients were treated with neoadjuvant chemotherapy together with trastuzumab. After 5 years, none of the patients who achieved pCR experienced locoregional-recurrence (reappearance of the cancer at or near the original site). Only 4% of patients who achieved pCR experienced metastatic recurrence (reappearance of the cancer in other organs of the body), compared to 20% of patients who did not achieve pCR. Furthermore, overall survival after 5 years was 95% for patients who achieved pCR, compared to 84% for patients who did not achieve pCR.

In summary, achievement of pCR to neoadjuvant chemotherapy among patients with HER2-positive breast cancer can be used to predict survival and recurrence.

A relatively small number of patients were included in this study. In addition, the retrospective manner in which this study was performed does not allow for a clear conclusion that pCR predicts prognosis independent of other factors.