Acute Myeloblastic Leukemia Relapse after Allogeneic Stem Cell Transplantation
Authors: Clémence Mediavilla , Vigouroux Stéphane , Tabrizi Reza , Clement Laurence , Banos Anne , Turlure Pascal , Lafarge Xavier , Dumas Pierre-Yves , Leguay Thibaut , Pigneux Arnaud , Milpied Noel , Forcade Edouard 
Published: October 2019

Abstract
Allogeneic haematopoietic stem cell transplantation (HSCT) is a curative option for acute myeloid leukaemia (AML). A major improvement of conditioning regimen has been realized in the last two decades, offering the opportunity for older patients to undergo HSCT with an acceptable toxicity profile. Unfortunately, relapse remains the main cause of death, and only few studies analyzed the survival of patients presenting with post-HSCT AML relapse and their treatment options. The purpose of this study was to analyze the survival of patients with post-HSCT AML relapse, to describe the treatment options and to search for factors associated with poor prognosis at relapse. In this study, we collected the data of all the patients transplanted between January 2005 and December 2014 at Bordeaux university centre and showing AML relapse after HSCT.
Between 2005 and 2014, out of 312 HSCT for AML, one hundred patients relapsed at our center with a median time from transplant of 123.5 days (11-2726 days). Median age was 55 years old (range 17-65), 44 patients were male. Donors were matched related for 49 patients, unrelated for 35 patients, and cord blood units were used in 16 patients. Conditioning regimen was reduced for 70 patients and myeloablative for 30 patients. According to the Disease Risk Index, 4 patients were considered at low risk, 29 patients at intermediate risk, 43 patients at high risk and 11 patients at very high risk. Thirty one per cent of patients had refractory disease. Before relapse, 31 patients developed Acute Graft Versus Host Disease (GVHD) and 9 patients developed Chronic GVHD. At relapse, 62 patients were still on cyclosporine and 22 on steroids. Eighty four patients presented an isolated bone marrow relapse, while 5 patients showed isolated extramedullary relapse, and 11 mixed relapse.
With a median follow-up from relapse of 106 days (0-3619 days), the 1 and 2-year overall survival (OS) were 24% and 13%, respectively. At final follow-up 8 patients were still alive. For alive patients, median follow-up from relapse was 1524 days (980-3619 days). Median age was 39 years old (20-57 years old), DRI was considered at intermediate risk for 2 patients, at high risk for 5 patients and at very high risk for 1 patient. No patient was FLT3 mutation.
In univariate analysis, factors associated with better OS at relapse were age < 45 years old, male gender, performance status at relapse > 70%, and no initial FLT3 mutation. Male gender, performance status at relapse, early relapse and no initial FLT3 mutation were associated with a better OS in multivariate analysis.
Seven patients responded to immunosuppression tapering and 19 patients to first line treatment containing local radiotherapy, chemotherapy and/or Donor Lymphocyte Infusion (DLI). Developing GVHD after immunosuppression tapering or DLI was associated to disease response: Seven patients responded after immunosuppression only of whom 4 after developing GVHD (p=0.0013). Twelve patients responded after DLI of whom 7 after developing GVHD (p=0.05). Patients receiving an association of chemotherapy and DLI showed a better response and a better survival compared to chemotherapy only (p= 0.03). Patients with FLT3 mutation did not respond to any treatment.
This study confirms the severity of AML relapse after HSCT with a poor long term OS. The particularly poor impact of FL3 mutation suggests the use of targeted therapy in a prophylactic setting. Immunomodulatory approaches resulted in disease response in some patients and should be evaluated prospectively to identify clinical and biological factors predictive of the response.

Disclosures
No relevant conflicts of interest to declare.