Trastuzumab deruxtecan demonstrated superior invasive disease-free survival compared to standard trastuzumab in patients with HER2-positive early breast cancer who had residual disease after neoadjuvant therapy. The antibody-drug conjugate combines the established HER2-targeting mechanism of trastuzumab with a potent topoisomerase I inhibitor payload, delivering cytotoxic therapy directly to cancer cells. This represents a significant advancement in post-neoadjuvant treatment strategies for high-risk breast cancer patients. The presence of residual disease after initial chemotherapy typically indicates a more aggressive tumor biology and higher recurrence risk, making this population particularly important for therapeutic innovation. Previous trials have established trastuzumab deruxtecan's efficacy in metastatic settings, but extending benefits to the adjuvant setting could prevent more cancers from progressing to advanced stages. The conjugated approach addresses limitations of traditional chemotherapy by reducing systemic toxicity while maintaining anti-tumor potency. For the estimated 15-20% of HER2-positive patients who don't achieve pathologic complete response to neoadjuvant therapy, this targeted approach offers a precision medicine solution that could fundamentally alter treatment paradigms and long-term outcomes in early-stage disease management.