Advances in chemotherapeutic and targeted agents have resulted in increased rates of pathologic complete response (pCR) rates after neoadjuvant systemic therapy (NST) for breast cancer. The pCR rates for triple-negative breast cancer (TNBC) and HER2-positive breast cancer are high as 50 and 70%, respectively. The results of large-scale meta-analyses suggest that patients with a pCR at surgery have favorable outcomes, with a 5-year disease-free survival rate of 85 to 90%.

        In patients with residual tumor after NST, surgery has an important role in removing cancer and providing evidence for additional adjuvant systemic therapy, such as capecitabine for TNBC or TDM-1 for HER2-positive cancers. However, if a patient had achieved a pCR, the role of surgery may be limited to “pathologic confirmation” of no residual tumor. Early trials conducted in the 1970-90s omitting surgery resulted in higher rates of local recurrence without surgery and thus it is the standard treatment to offer breast and axillary surgery after NST. However, data from these studies suggested that when a complete clinical response is predicted with appropriate diagnostic methods, the local recurrence rates are comparable to those who receive a breast-conserving surgery.

        Diagnostic imaging and biopsy techniques have improved greatly over the years. Recent feasibility and phase II studies evaluating the accuracy of imaging-guided biopsy to assess pCR in exceptional responders to NST have shown promising results. It is suggested that in patients with a radiologic complete response or minimal residual lesion of less than 1~2 cm on imaging, a sufficient number of tissues (≥ 5~6 cores) sampled with a vacuum-assisted biopsy (VAB) using a 7~10 gauge needle could predict a pCR with a negative-predictive value of > 90% and a false-negative rate of < 10%.

        In this talk, I will be introducing currently ongoing or planned trials regarding optimization (rather than de-escalation) of breast cancer surgery after neoadjuvant chemotherapy, including the OPTIMIST trial planned in Korea. It is a multicenter, single-arm, non-inferiority trial evaluating the safety of omission of surgery for patients with a pCR diagnosed with MRI and VAB. It is planned to start enrolling patients by August, 2022.