The emerging role of immune checkpoint inhibitors for the treatment of breast cancer.

A number of novel combination strategies are under investigation to enhance response and overcome resistance to immunotherapy, with promising preliminary data from checkpoint inhibitors targeting TIGIT, combinations with small molecule inhibitors such as lenvatinib, and injectable agents directly influencing the immune microenvironment. As immunotherapy enters into the curative setting, biomarkers predictive of immunotherapy benefit are needed, as PD-L1 status has not been a helpful discriminator in completed trials in early-stage breast cancer.