Immunotherapy in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of mammary carcinoma. A subset of TNBC is immune activated, suggesting that immunotherapy may be a viable treatment strategy. Phase III clinical trials have shown that atezolizumab or pembrolizumab is well-tolerated in combination with chemotherapy, with progression-free survival benefit in metastatic programmed death ligand-1 (PD-L1)-positive TNBC patients treated first line. Based on IMpassion130, the combination of atezolizumab and nab-paclitaxel is now considered a standard of care for the treatment of PD-L1-positive advanced TNBC. In early TNBC, pembrolizumab and atezolizumab have been tested in combination with standard neoadjuvant chemotherapy, resulting in a higher complete pathologic response rate than standard neoadjuvant chemotherapy alone, regardless of disease PD-L1 status. These findings establish proof of principle for immunotherapy in both early and advanced TNBC. High priorities for the field include developing more active immunotherapy combination regimens and more refined biomarkers that optimally identify patients most likely to benefit from immunotherapy.