To explore the efficacy and safety of thiotepa combined with melphalan for ASCT conditioning in patients with multiple myeloma who did not acheive CR with or without extramedullary inflitration before transplantation.

After screening and enrollment, the patients were randomly divided into two groups according to 1:1, and the experimental group received the following drug treatments: the total amount of thiotepa was 10mg/kg, D-4 to -3; melphalan 140mg/m2, D-2. The control group received melphalan 200mg/m2, D-2 (the dose of the drug was adjusted according to the glomerular filtration rate). The two groups of D0 infused hematopoietic stem cells.G-CSF and TPO or TPO-RA were allowed to use to promote hematopoietic stem cell engraftment.Platelet and red blood cell transfusions were allowed if necessary. Efficacy of the therapy was evaluated 1 month after the end of transplantation, and the follow-up evaluation was carried out every 3 months, and the relapse rate was evaluated until 1 year after transplantation.

Inclusion Criteria:

• 1) Age 18-70 years old, gender is not limited; 2) Patients with confirmed multiple myeloma; 3) CR is not achieved before transplantation after treatment with or without extramedullary lesion invasion; 4) plan to undergo autologous hematopoietic stem cell transplantation; 5) recieve autologous hematopoietic stem cell transplantation within 12 months; 6) CD34 positive cell counts ≥2×106/kg; 7) The function of major organs is normal, and the laboratory test results meet the following criteria: a. Alanine aminotransferase (ALT) ≤3.0× upper limit of normal (ULN) aspartate aminotransferase (AST) ≤3.0×ULN; b. Serum total bilirubin ≤ 1.5×ULN; 8) Voluntarily participate in this clinical trial, understand the research procedures and be able to sign the informed consent forms

Exclusion Criteria:

• 1) Do not have indications for autologous hematopoietic stem cell transplantation; 2) presence of uncontrolled active infection (HIV-positive, positive for HBV-DNA and HCV-RNA quantitative tests); 3) severe respiratory diseases; 4) Severe abnormal liver function; 5) a second transplant is required; 6) Clinically significant or uncontrolled heart disease (grade III or IV congestive heart failure, EF<45%, BNP>5000ng/ml, TnT>0.06ug/L, oxygen saturation <95%, any of which) 7) Patients with other solid tumors; 8) Those who are allergic to setepa and the drug involved in the study or have a more serious allergic constitution; 9) Those who participate in other clinical research at the same time; 10) Other conditions judged by the investigator to be unsuitable for inclusion in this study.