Study on the Efficacy and Safety of Low-dose CTX as Maintenance Therapy for MM Unsuitable for Transplantation

Inclusion Criteria: 1. After induction and consolidation therapy (8 courses of chemotherapy), MM patients in the standard-risk group who were initially unsuitable for transplantation achieved a therapeutic effect of VGPR or above; 2. Secretory MM with measurable indicators; 3. Age ≥ 18 years old, gender unlimited; 4. No obvious dysfunction of heart, lungs, etc. (≤ Grade I); 5. General KPS ≥ 70% (excluding those caused by pathological fractures and bone pain). Exclusion Criteria: 1. Cytogenetic high-risk patients; 2. Recurrent or refractory MM; 3. Using autologous hematopoietic stem cell transplantation as a consolidation therapy; 4. The therapeutic effect did not reach VGPR or above before enrollment; 5. Asymptomatic MM; 6. No measurable indicators; 7. KPS\<50%(excluding those caused by pathological fractures）； 8. Dysfunction of heart, lungs, etc. (\> Grade I); 9. Unable to cooperate in observing adverse reactions and therapeutic effects; 10. Pregnancy, breastfeeding, or refusal of contraception by women; 11. There is drug abuse and medical, psychological, or social conditions that may interfere with patients participating in research or evaluating research results; 12. Any unstable or potentially endangering patient safety and compliance with the study.