VEN+DAC+Bu2Flu4 vs Bu2Flu5 Conditioning Regimen for Elderly Myeloid Malignancies Undergoing Allo-HSCT

The purpose of this study is to compare the efficacy and safety of venetoclax+decitabine+busulfan+fludarabine (VEN+DAC+Bu2Flu4) regimen with busulfan+fludarabine (Bu2Flu5) regimen in older patients with myeloid malignancies undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT).

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potent curative approach for myeloid malignancies, but outcomes post-transplantation of older population were unsatisfactory. The conditioning regimen is an essential factor affecting outcomes post-transplantation. Currently, the optimal conditioning for older patients with myeloid malignancies remains unclear. Myeloablative conditioning (MAC) regimens like busulfan plus cyclophosphamide, and busulfan plus fludarabine (Bu4Flu4-5) have low relapse rates, but high non-relapse mortality (NRM) is observed in older patients with myeloid malignancies. The development of reduced-intensity conditioning (RIC) regimens such as Bu2Flu5 has decreased NRM and enhanced the feasibility of allo-HSCT in older patients with myeloid malignancies, but it appears to have higher relapse rate. Neither conventional MAC nor RIC regimens benefit older patients with myeloid malignancies. In recent years, some studies reported that the introduction of venetoclax (VEN) or decitabine (DAC) to MAC reduced relapse without increasing NRM in younger patients with high-risk myeloid malignancies. However, whether VEN and DAC combined with RIC regimen reduce relapse without increasing NRM, then improve survival in older patients with myeloid malignancies is unclear. Therefore, we conducted a randomized controlled study to compare the efficacy and safety of VEN+DAC+Bu2Flu4 with Bu2Flu5 in older patients with myeloid malignancies undergoing allo-HSCT.