Dendritic Cell Immunotherapy for De Novo HER2+ Metastatic Breast Cancer

Introduction: Intratumoral delivery of conventional dendritic cells (cDC1) offers a promising new immunotherapy strategy for HER2-positive breast cancer by activating CD4 Th1 cells and other innate immune components.Case presentation: We present a case series of two young women presenting with de novo metastatic HER2-positive breast cancer treated with cDC1 therapy alongside HER2-targeted and endocrine therapies.The patients tolerated the treatment well and showed encouraging outcomes, including tumor reduction, healing of metastatic sites and early immune responses before starting chemotherapy.Imaging revealed significant partial responses or no active disease, and blood analyses confirmed immune activation.Conclusion: These findings demonstrate the feasibility and safety of cDC1 intratumoral therapy as an early intervention and suggest its potential role in improving clinical outcomes.Further research is warranted to refine patient selection and treatment regimens for optimal integration into standard care for metastatic HER2-positive breast cancer.