Torben Plesner, MD, from the Vejle Hospital and University of Southern Denmark, Vejle, Denmark, discusses the pros and cons of increasing CD38 expression at the 2017 World Congress on Controversies in Multiple Myeloma (COMy) in Paris, France. The role of CD38 expression in myeloma cells is still unclear, however, it is currently thought that a high expression leads to an increased response from daratumumab. There are current ongoing trials using drugs to increase CD38 expression, to test this theory. Dr Plesner states that he is concerned about increasing CD38 expression, as it may lead to resistance to other treatments.