In an interview conducted at the 2021 European Myeloma Network (EMN) congress, Heinz Ludwig, MD, of the Wilhelminen Cancer Research Institute, Wilhelminenspital, in Vienna, Austria, discusses response monitoring in multiple myeloma. He highlights the challenges of response monitoring in patients with long-standing disease, where tumor cell proliferation and paraprotein production by individual tumor cells may become uncoupled. Prof Ludwig explains that this uncoupling may contribute to misleading results for the analysis of disease progression, highlighting the need for clinicians to use other parameters to assess disease progression.