Immune Checkpoint Blockade for Breast Cancer.

An effective antitumor immune response requires interaction between cells of the adaptive and innate immune system. Three key elements are required: generation of activated tumor-directed T cells, infiltration of activated T cells into the tumor microenvironment, and killing of tumor cells by activated T cells. Tumor immune evasion can occur as a result of the disruption of each of these three key T cell activities, resulting in three distinct cancer-immune phenotypes. The immune inflamed phenotype, characterized by the presence of a robust tumor immune infiltrate, suggests impaired activated T cell killing of tumor cells related to the presence of inhibitory factors. Programmed death receptor-1 (PD-1) is an inhibitory transmembrane protein expressed on T cells, B cells, and NK cells. The interaction between PD-1 and its ligands (PD-L1/L2) functions as an immune checkpoint against unrestrained cytotoxic T effector cell activity-it promotes peripheral T effector cell exhaustion and conversion of T effector cells to immunosuppressive T regulatory (Treg) cells. Immune checkpoint inhibitors, which block the PD-1/PD-L1 axis and reactivate cytotoxic T effector cell function, are actively being investigated for the treatment of breast cancer.

Impact of tissue-based genomic profiling on clinical decision making in the management of patients with metastatic breast cancer at academic centers.

BACKGROUND: Genomic profiling can identify targetable mutations; however, the impact of tissue-based genomic profiling on clinical decision making for patients with metastatic breast cancer has not been well characterized. METHODS: Patients with stage IV breast cancer who had undergone genomic profiling between 7/2013 and 3/2015 were identified at three academic cancer centers. Genomic analysis was determined to have impacted clinical decision if (A) a patient was enrolled onto a genotype-matched clinical trial or (B) prescribed off-label an FDA-approved therapy targeting an identified mutation. The frequency of mutated genes was determined. RESULTS: A total of 117 patients with stage IV breast cancer were identified. Median age was 46 (25-75). Fifty-three patients (45%) had ER-positive/HER2-negative disease, 50 (43%) had ER-negative/HER2-negative disease, and 14 (12%) had ER-any/HER2-positive disease. Median number of previous therapies received prior to genomic profiling was 2 (range 0-15), and median follow-up after testing was obtained after 5.8 months (range 0-24.4 months). Commercial reports indicated that 85 (73%) patients had at least one mutation targetable by an FDA-approved medication, and 112 (96%) patients had at least one clinical trial available; however, clinical management was only affected in 11 patients (9%). The most frequent mutations observed were those in TP53, FGF, PI3KCA, MYC, ZNF, FGFR, CCND, ARID1A, GATA3, and MAP; frequencies of these mutations varied by clinical subtype. CONCLUSIONS: Tumor genomic profiling affected clinical management in a minority of patients with metastatic breast cancer, thus these data do not support the routine use of genomic profiling outside of a clinical trial.