Individualized tumor response testing (ITRT) has a long history, with a number of different technologies and many different tumor types tested. Almost all technologies used for hematological malignancies are identical in their logic and similar in their execution. The concepts underlying cell death assays are relatively simple, even though the technical features and data interpretation can be complex. The logic is that if the drug kills tumor cells from an individual patient in a “test tube,” then it is more likely to be effective when administered directly to a patient. Conversely, a drug that does not kill the patient’s cells, even at concentrations significantly higher than can be achieved in the patient, is unlikely to be effective. Considerable work based on these assays has been reported during the past 25 years, and recently an ad hoc group of 50 scientists from 10 countries agreed on the term “individualized tumor response” for these 24tests, describing them as the “effect of anticancer treatments on whole living tumor cells freshly removed from cancer patients” and not including tests with “subcellular fractions, animals or cell lines” (1).