Hematopoietic Stem Cell Microtransplantation in Patients Aged over 70 with Acute Myeloid Leukemia: a Multicenter Study

In the era of molecular targeted drugs, elderly patients with acute myeloid leukemia (AML) are still very difficult to treat, especially those older than 70 years. The decline in immune function leads to serious infection and disease recurrence. The microtransplant treatment regimen (MST) chemotherapy combined with allogeneic hematopoietic stem cell infusion is a new cell therapy regimen. The aim of this MST study was to improve the survival of elderly patients by graft versus leukemia action and improving T-cell immune function. From May 2012 to July 2020, one hundred and eleven patients aged 70 to 88 years with de novo AML were analyzed retrospectively. After induction chemotherapy, patients whom complete remission (CR) was achieved were given another 2 cycles of postremission therapy. The MST groups were given allogeneic stem cell infusion after each chemotherapy cycle. CR, leukemia-free survival, and overall survival (OS) were compared between groups. Additionally, the immune function and the T cell receptor (TCR) library of T cells were detected and analyzed. The MST group exhibited an encouragingly high CR rate (63.8%), even in high-risk patients (54%), and this rate was significantly higher than that in the chemotherapy alone group. The 1-year OS of MST patients was 57.7%, and it was 55.9% in the high-risk group. It was only 37.3% in the chemotherapy alone group. Higher numbers of naive T cells were found in the MST population than in the chemotherapy alone group. More updated T-cell clones were observed in MST patients by T-cell receptor repertoire analysis with a next-generation sequencing methodology. These results suggest that MST is a safe and practical regimen conducive to longer-term survival in patients of a highly advanced age with AML. Furthermore, it has broad clinical value in the recovery of immune function in elderly patients.