This study aimed to evaluate the efficacy of reduced intensity conditioning (RIC) regimen in elderly or high comorbidity burden patients who receive haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Haplo-HSCT is an effective treatment option for patients who did not have identical sibling donor (ISD) or unrelated donor (URD). However, post-transplant transplant-related mortality (TRM) is one of the major causes for transplant failure, and the risk of TRM for old patients or those with high comorbidity burden was higher. RIC regimen may decrease the risk of TRM for haplo-HSCT recipients. The study hypothesis: Using RIC haplo-HSCT regimen in elderly patients or those with high comorbidity burden can reduce TRM and improve survival.