Multiple myeloma (MM) is a type of cancer of the white blood cells, called plasma cells. These plasma cells help in fighting infections. TCR-MM is when the cancer does not get treated with the 3 main classes of medicines used to treat this disease. The purpose of this study is to learn about the present clinical practice in Italy and describe the standard of care that will be given to patients with TCR-MM, and their treatment costs, in around 25 centers who treat patients with blood diseases. Standard of care (SoC) is the treatment that is accepted as a proper treatment for a certain type of disease and that is widely used by doctors. The study is seeking for participants who are: * 18 years of age or older * Confirmed to have MM * do not show any response when treated with the 3 main classes of medicines used to treat MM Data of participants who received the TCR treatment between 01 December 2021 and 31 May will be collected. The main data source for the study will be the patient medical record. No clinical visits, examinations, or procedures are required as part of this study.