Checkpoint inhibitors in breast cancer - Current status

An increasing number of compounds directed against immune checkpoints are currently under clinical development. In this review we summarize current research in breast cancer.

A computer-based literature search was carried out using PubMed and EMBASE; data reported at international meetings and clinicaltrials.gov were included as well.

The obtained overall response rate of PD-1/PD-L1 monotherapy varied from 5 to 30% in heavily pretreated triple negative breast cancer (TNBC). The median duration of progression free survival and overall survival were either not reported or short. Still responses were of long duration in a subset of patients. In the neoadjuvant setting, preliminary results including a very limited number of patients suggest high pathological response rates after combined blockade of the PD-1 pathway and chemotherapy. Multiple trials have been initiated to evaluate the combination of other anticancer agents and checkpoint inhibitors, especially in TNBC. In addition, ongoing studies aim to identify biomarkers to guide patient selection.

Immune checkpoint inhibitors have the potential to produce durable tumor remission and induce long standing anti-tumor immunity in a subgroup of breast cancer patients. However, the identification of predictive biomarkers is crucial for further development of this treatment modality.