Intratumoral Immunotherapy in Breast Cancer

Breast cancer remains the most frequently diagnosed cancer and the second highest cause of cancer death in females. Metastatic recurrence that is resistant to traditional therapies presents a major challenge, necessitating the development of an innovative treatment strategy. Immunotherapy has gained popularity in the treatment of cancer, particularly melanoma, lung cancer, and more recently breast cancer. Major developments in immunotherapy have been made with a better understanding of the tumor microenvironment and how the microenvironment can be manipulated to induce an anti-tumor immune response. Intratumorally delivered immunotherapy can be used to create a local immune response. This review provides a comprehensive overview of intratumoral immunotherapy for breast cancer and its resultant changes in the tumor microenvironment. The discussed immunotherapeutics include oncolytic viruses, nucleic acids, innate immune agonists, bacteria, chimeric antigen receptor T cells, and dendritic cells. The review also evaluates completed clinical trials using these therapies. Lastly, the review offers future perspectives in the development of breast cancer immunotherapy.