Generally, hematopoietic stem cell transplantation can be performed when the disease is in remission, but if the disease is not in remission, the risk of relapse after transplantation is high. 1. In order to avoid recurrence of the disease after hematopoietic stem cell transplantation, systemic irradiation, chemotherapy and immunosuppressive treatment are needed before transplantation, so that hematopoietic stem cell transplantation can be carried out after the disease has reached remission, and the specific medicines include cytarabine, fludarabine and so on. 2. If the disease is not in remission, especially for malignant blood diseases such as leukemia, the original cancer cells may re-emerge after HSCT, leading to recurrence of the original disease. It is up to the doctor to decide under what circumstances a hematopoietic stem cell transplant can be performed according to the specific condition. It is recommended to follow the doctor’s advice.