Trastuzumab deruxtecan adjuvant treatment of high-risk HER2-positive, residual invasive breast cancer after neoadjuvant therapy

Breast cancer occurs when abnormal cells in the breast grow and divide uncontrollably, forming a tumour. Cancers that have high levels of a protein called human epidermal growth factor receptor 2 (HER2) on the cell surface are called HER2-positive cancers, making them more aggressive and prone to rapid spread and growth compared to HER2-negative cancers. Neoadjuvant therapies, such as chemotherapy combined with trastuzumab and pertuzumab, are used before surgery to shrink tumours and improve surgical outcomes for patients. If cancerous cells remain in the breast or surrounding lymph nodes after neoadjuvant treatment, they are called ‘residual invasive disease’. The presence of residual invasive disease increases the risk of cancer recurrence, spread to other parts of the body (metastasis) or death. However, additional adjuvant therapies post-surgery can reduce this risk in early-stage breast cancer.