Triple-negative breast cancer (TNBC) defined by lack of estrogen, progesterone, and the HER2 receptor accounts for 15% of all newly diagnosed breast cancers. With limited treatment options, the median overall survival of these patients is just over one year. TNBC as compared to other subtypes of breast cancers are more likely to have a robust immune infiltrate and have a high level of tumor-infiltrating lymphocytes.
They can also have a higher level of PD-L1 expression and are generally genetically unstable and have a high tumor mutation burden. This makes this tumor type amenable to different therapies.