De-escalation of perioperative systemic therapy for early breast cancer.

Breast cancer is the most common malignancy among women worldwide, and the number of survivors continues to increase owing to earlier detection and advances in treatment. As long-term survivorship becomes increasingly important, minimizing treatment-related toxicity without compromising oncologic outcomes has become a major goal in the management of early breast cancer. Treatment de-escalation strategies have therefore attracted considerable attention. In HER2-positive disease, several approaches have been explored, including reduction of chemotherapy intensity, shortening the duration of anti-HER2 therapy, chemotherapy-free regimens in selected patients, and response-guided strategies based on pathologic complete response following neoadjuvant therapy. In hormone receptor-positive HER2-negative breast cancer, multigene expression assays have enabled more precise risk stratification and have allowed omission of adjuvant chemotherapy in patients with biologically low-risk tumors. In addition, the neoadjuvant setting provides an opportunity to evaluate treatment response using biomarkers such as Ki67, which may help identify patients who can safely avoid chemotherapy. Ongoing clinical trials are further evaluating response-guided treatment strategies, particularly in premenopausal patients. Furthermore, circulating tumor DNA has recently emerged as a promising biomarker for detecting minimal residual disease and monitoring treatment response. Integration of molecular biomarkers with response-adapted strategies may further refine risk stratification and support personalized treatment approaches. This review summarizes current evidence and ongoing studies on treatment de-escalation across breast cancer subtypes.