ATYPICAL RESPONDERS LANDSCAPE REVIEW ∙ OCTOBER, 2017 37 Assay: a measurement performed on a biological sample Basket trial: a clinical trial in which researchers test the effect of a single drug on a specific mutation in a variety of cancer types Biomarker: a quantifiable biological molecule such as a protein, DNA, RNA, or biological compound that is measured in a biological sample (blood, DNA, a tumor, etc.) and that acts as an indicator for a specific biological state or condition. In the context of personalized cancer therapy, biomarkers are used to determine patient prognosis and predict which patients will have the highest likelihood of responding to selected therapies or have adverse side effects with particular therapies. Biomarker tests are currently being used to predict the likelihood of benefit, which integrates both sensitivity and resistance to targeted therapies [86]. Chemokines: cytokines that attract cells to a site of infection or inflammation Chemoresistance: low or no response to a drug that is generally considered effective in many tumors Chemosensitivity: exquisitely high response to a drug in which tumor cells die more quickly or at a much lower drug concentration compared to many other tumors Cohort study: a study of a group of patients with certain similarities, such as a particular disease or treatment at a particular hospital or institute who are followed up over a period of time. In contrast to many clinical trials, cohort studies are observational, meaning that patients in a cohort receive standard of care as determined by their physicians rather than novel treatments such as in a clinical trial; researchers observe a cohort and intervene in a clinical trial. In addition, unlike many clinical trials, cohort studies can be carried out over many years or decades and can thus be used to obtain much longer-term data than typical clinical trials. Cohort studies can be retrospective, meaning that data for a group of patients are examined after the patients have been treated, or prospective, meaning that researchers will enroll patients in their cohort with selected characteristics (for example, all patients with a certain disease treated at a certain institute who underwent a particular imaging technique or received a certain treatment). Carefully defined cohort studies can establish a cause between two events. Co-morbidity: other diseases or conditions the patient may have Complete response (CR): disappearance of all indications of a disease such as cancer following a treatment Cytochrome: proteins that carry iron and that function in metabolism Cytokines: a group of small molecules released by immune cells that affect the nearby cells Cytoskeleton: the scaffold of proteins located inside cells that determines the shape of the cells and that helps cells move Glossary