Cancer Genetics, Inc. announced the expansion of its immuno-oncology (IO) panel, Complete::IO™, to include five new IO markers. This brings the total number of markers it simultaneously detects to 27, making Complete::IO™ the most comprehensive flow-cytometry-based biomarker panel in the industry, with a 24-hour turn around time. Since its launch in April 2017, Complete::IO has quickly gained commercial traction and has already been included in notable immunotherapy trials including studies of CAR-T therapies and checkpoint inhibitors. Complete::IO™ is a multi-marker panel enabling comprehensive characterization of the immune repertoire of cancer patients, including circulating immune cell populations and the tumor microenvironment. It plays a unique role in identifying ideal patient populations for specific IO therapies and addresses the unmet need to monitor and stratify patient populations during clinical trials. The panel also assures that patients are monitored for safety and toxicity throughout the trial. The increased number of markers allows for the identification of rare and challenging subsets of immune cells. Besides the commonly studied subsets, central memory, effector, effector memory cells, naïve CD4+ and CD8+ T cells, T-regs, B-regs, NK, and plasmacytoid dendritic cells, Complete::IO™ is now able to power highly accurate immunophenotyping and the measurement of the frequency of myeloid-derived suppressor cells (MDSCs), as well as those that express PD-1, PD-L1, or PD-L2. The presence and frequency of MDSCs, which inhibit anti-tumor immune response, in the blood of cancer patients, might represent a novel and accessible biomarker to monitor clinical outcome and response to therapy. In addition, targeting MDSCs to increase the efficacy of immunotherapeutics appears to be a clinically promising strategy, and is being actively evaluated in clinical trials. According to industry reports, there are over 2,500 active clinical trials globally related to IO therapies. The addition of PD-1, PD-L1 and PD-L2 to the panel is in concert with recent studies associating the expression of these markers by tumor cells and/or immune cells in the tumor microenvironment with clinical efficacy of IO therapies. Flow cytometry as compared to other methods has the advantage of simultaneously measuring the expression of PD-1 and its ligands PD-L1 and PD-L2 in malignant cells and various types of immune cells. This provides a more comprehensive understanding of PD-1/ligand interactions between tumor cells and the immune environment.