Checkpoint Inhibitors in the Treatment of Breast Cancer

The treatment landscape for many cancers has dramatically changed with the development of checkpoint inhibitors. This article will review the literature concerning the use of checkpoint inhibitors in breast cancer. The histological subtype of BC with the strongest signal of efficacy has been triple-negative breast cancer (TNBC). Early trials of single-agent checkpoint inhibitors did not demonstrate a uniformly positive signal. Clinical studies suggest response rates between 5 and 10% in pretreated patients and roughly 20-25% for untreated advanced TNBC. However, in the small subset of patients who do respond, the response is often durable. More encouraging results have been reported with their use in combination with chemotherapy in the neoadjuvant setting. Larger phase III studies are underway to confirm these earlier findings. An immune-directed therapeutic approach for the management of BC is underway, and it is likely that combination therapy will be required to achieve a level of efficacy worthy of use in the BC treatment paradigm. These agents are not without both economic and clinical toxicity; therefore, it is imperative that we identify patients most likely to benefit from these therapies through well-designed biologically plausible clinical studies and by evaluating novel combinatorial approaches with informative biomarker driven correlative studies.