Survival of AML Patients Relapsing after Hematopoetic Stem Cell Transplantation: A Single Center Experience
Authors: Aytan Pelin , Yeral Mahmut , Korur Aslı , Gereklioglu Cigdem , Tanrıkulu Funda , Kasar Mutlu , Solmaz Soner , Buyukkurt Nurhilal , Asma Suheyl , Kozanoglu Ilknur , Ozdogu Hakan , Boga Can 
Published: October 2019

Abstract
Although it is presumed to be a curative strategy for intermediate and high risk acute myeloid leukemia (AML), many patients relapse after allogeneic hematopoietic stem cell transplantation. This prompt us to examine the ways to improve the outcomes. We retrospectively evaluated 76 AML patients who were transplanted between 2007-2017 years in our clinic. We tried to identify the factors associated with posttransplant relapse, postrelapse survival and if there was a survival benefit of pretransplant consolidation and minimal residual disease (MRD) negativity. We examined the effect of the acute-chronic graft versus host disease (GVHD) and salvage therapy after the posttransplant relapses. The mean age of the patients was 44.6±1.21 years (ranges 21-67). 42.1% were females and 57.9% were males. 43.3% of the patients were in complete remission (CR) MRD positive state before the transplantation whereas 35.5% were in CR MRD negative and 3.9% were in progressive disease state. In 13 patients who were in CR state, the MRD status were not known. 11 (14.5%) patients were considered as in favorable risk, 52 (68.4%) in intermediate risk and 13 (17.1%) in unfavorable risk with respect to cytogenetic analysis before the transplantation. The donors were HLA compatible relatives (77.6%), HLA compatible non-relatives (10.5%), haploidentical people (9.2%), one HLA incompatible relative (1.3%) and one HLA incompatible nonrelative (1.3%). 74 bone marrow transplantations (97.4%) were allogeneic and the remaining two (2.6%) were autologous. Myeloablative conditioning regimen was applied to 57 patients (75%) and 19 patients got (25%) reduced intensity conditioning regimen. GVHD developed in 51.3% after transplantation and 61.5% of these were chronic extensive. Relapse occurred in 27 patients (35.5%), hematological relapse being the most common (31.6%). The median time for the development of relapse was found to be 5.5 months (range: 1.5-37). The overall probability for the development of a relapse was found to be 48.7% (95% CI: 40.9-56.5)(Figure1A). 23 patients (30.3%) died during the study period with a median survival of 9.6 months (range: 1.6-45). In the studied population the overall survival probability was found to be 52.8% (95% CI: 45.4 - 60.2) [Figure 1B]. 36.4%, 28.8% and 30.8% of the patients with favorable, intermediate and unfavorable cytogenetic status died respectively during the study period. The comparison of the survival probability of the patients with favorable, intermediate and unfavorable cytogenetic status was depicted in Figure 2. The overall survival probability of the patients with favorable, intermediate and unfavorable cytogenetic status were 46.6% (95% CI: 26.2-66.9), 54.6% (95 % CI: 45.9 - 63.2) and 36.9 % (95% CI: 25.4 - 48.5) respectively (p=0.807).
MRD status of 60 patients were known. At the end of the study period 75.8% of the CR MRD positive and 70.4% of the CR MRD negative patients remained alive. The comparison of the survival of patients in CR with respect to MRD status is shown in Figure 3. The overall survival probability of CR MRD positive patients was 56.3 % (95% CI: 45.3 - 67.3) and this rate was 52.5 % (95% CI: 40.8 - 64.3) in MRD negative patients (p=0.770) [Figure 3].
Patients who developed GVHD had similar overall survival probability with the patients who did not developed the disease; 47.0% vs 57.2%, p=0.115 (Figure 4A). Even the patients with chronic extensive GVHD had similar overall survival rates with the patients who had none or acute GVHD; 49.3 % vs 58.2%, p=0.27 (Figure 4B).
66.7% of the patients with a progressive disease before the transplantation died during the study period and this rate was 27.1% in the patients with CR (p=0.005).
In conclusion the overall survival rate of the transplanted AML patients was 52.8% in the study group. The overall survival did not seem to be affected by pre-transplant MRD status, cytogenetic risk factors and administration of consolidation therapy. The only patients who had significantly worse results were the ones who had progressive disease before the transplantation. From this point it would be logical to make transplantation whenever the patient is in first CR regardless of the MRD status and a matched donor is found so that the toxic effects of the consolidation chemotherapy may be prevented.

Disclosures
No relevant conflicts of interest to declare.