Long-Lasting Response after Pembrolizumab in a Patient with Metastatic Triple-Negative Breast Cancer

Introduction Breast cancer is the first cause of cancer death in women. The triple-negative subtype is associated with aggressive behavior and poor prognosis. Chemotherapy is the main therapeutic option available for these patients, but it is usually associated with short overall survival. Case Presentation We report the case of a patient diagnosed with metastatic triple-negative breast cancer with an impressive long-lasting tumor response and long-term survival after pembrolizumab monotherapy. Conclusion Immunotherapy is emerging as a promising treatment for some breast cancer patients. Nevertheless, monotherapy studies have shown a very limited activity. Nowadays, there is no good predictor biomarker. Further investigations are needed to identify the subgroup of patients who can benefit from checkpoint inhibitor treatment.