It's not 'just a tube of blood': principles of protocol development, sample collection, staffing and budget considerations for blood-based biomarkers in immunotherapy studies.

Immunotherapy for cancer is now a standard pillar in the armamentarium of treatments for many cancers. Immune checkpoint inhibitors, in particular, have resulted in significant therapeutic benefit and prolongation of survival in solid organ cancers, such as melanoma and lung cancer. However, the extent of benefit is not uniform. There are several groups studying predictors of benefit from these therapies. Recently, there has been a burgeoning interest in studying predictive biomarkers from the blood. These markers include circulating tumor DNA, circulating tumor cells, lymphocyte subpopulations, exosomes and metabolites to name a few. The logistics involved in such biomarker work are complex and rigorous with potential to impact a given study. Such pre-analytic components include development of a rigorous protocol, standard operating procedures for collection and storage of various blood components, ethics of patient consent, personnel involved as well as budget considerations. In this primer, we lay out representative aspects of each of the aforementioned components as a guide to blood-based biomarker research for immunotherapy studies in cancer.