Allogeneic Stem Cell Transplantation (SCT) in Untreated First Relapse or Following Re-Induction Chemotherapy for Patients with Acute Myeloid Leukemia (AML).
Authors: Pornvipavee Rachanid , Kremers Walter K. , Pedersen Rachel A. , Elliott Michelle , Hogan William J. , Tefferi Ayalew , Litzow Mark Robert 
Published: October 2019

Abstract
Background
The timing of SCT for treatment of AML after first relapse is controversial, i.e.,whether to proceed to SCT at the time of relapse or to proceed to chemotherapy re-induction first in an attempt to reach a second remission. The purpose of this study is to determine the optimal time of allogeneic SCT in AML patients in first relapse by comparing outcomes of allogeneic SCT between patients untreated and patients post re-induction chemotherapy.
Method
This retrospective study was approved by the Mayo Foundation IRB. Between February 1983 and March 2003, 60 patients with AML in untreated first relapse (REL1) or post re-induction chemotherapy (CT) underwent allogeneic SCT in Mayo Clinic, Rochester. Study outcome included overall survival (OS), disease free survival (DFS), and transplant related mortality (TRM). The outcome was compared between the patients who underwent allogeneic SCT at REL1 and CT. Survival was analyzed using Kaplan-Meier (KM) and groups were compared statistically with the log-rank test.
Result
Of the 60 patients receiving allogeneic SCT , 25 patients and 35 patients underwent SCT at REL1 and CT, respectively. In the group of CT, 23 patients (66%) achieved CR2 while 12 patients (34%) had refractory disease. Forty-nine of 60 patients received cyclophosphamide and total body irradiation (Cy/TBI) as a conditioning regimen and the remainder received busulfan and cyclophosphamide( Bu/Cy). Patients in REL1 were older at SCT (median age 38 vs 31 years p= 0.024 ) and had lower percentage blast cells in bone marrow at first relapse (median 15% vs 50% p=0.00095) than in CT group. Difference in other baseline characteristics were not significant. KM analysis showed that the two groups did not show statistically differences in OS (p=0.43), DFS (p=0.68), and TRM (p=0.25). However, there were trends toward longer median OS (26.2 vs 5.4 months) and DFS (11.9 vs 3.3 months) with REL1 versus CT. OS at 1 year was 56 % for REL1 and 34.3 % for CT and at 5 year 32.1 % and 28.6 %, respectively. DFS at 1 year was 48 % for REL1 and 31.4 % for CT and at 5 years 22.9 % and 24.5 % respectively. TRM at 1 year was 25% for REL1 and 40 % for CT. A univariate Cox Proportional Hazard analysis for survival showed that unfavorable cytogenetics at diagnosis and relapse, antecedent MDS, and shorter duration of CR1 were significantly associated with a higher risk of death. Higher percentage of blast cells in bone marrow at first relapse was not significantly associated with a higher risk of death. In a multivariate model, unfavorable cytogenetics at first relapse and shorter duration of CR1 were both significantly associated with an increased risk of death. In this study, even after adjusting for other factors in a multivariate model, the difference between REL1 and CT groups was not statistically significant.
Conclusion
This study suggests that outcome of allogeneic SCT was comparable between REL1 and CT. Patients with AML in first relapse may proceed to allogeneic SCT because there appear to be no statistical differences in REL1 versus re-induction chemotherapy before SCT. REL1 patients tended to have a better outcome than CT patients.