Outcomes for Allogeneic Stem Cell Transplantation in Secondary AML Are Inferior to De Novo AML and Are Independent of the Disease Risk Index

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Abstract Background Patients with secondary acute myeloid leukaemia (sAML), defined as AML that follows a diagnosis of myelodysplastic syndrome or myeloproliferative neoplasm, are known to have a poor prognosis with conventional chemotherapy alone, when compared to de novo AML (dnAML). Allogeneic stem cell transplant offers the best chance of cure due to the often chemo-resistant nature of sAML, although there are limited studies assessing the outcome of allografting in this patient population. The Disease Risk Index (DRI) is a clinical decision tool which assists in determining the balance of transplant risk versus benefit, however validation studies to date have not evaluated the DRI in patients with sAML. Methods A retrospective analysis of 211 patients with dnAML or sAML who underwent allogeneic stem cell transplant between 1 st January 1998 and 31 st July 2015 at St Vincent's Hospital or Royal North Shore Hospital in Sydney Australia, was undertaken. Cases were identified from the Australasian Bone Marrow Transplant Recipient Registry, with additional data collected by medical record review. Overall survival (OS) probability was calculated by the Kaplan-Meier method. Non-relapse mortality (NRM) and relapse incidence (RI) were estimated by cumulative incidence with "death without relapse" and "relapse" as competing risks. A Cox proportional hazards model was used for multivariate regression, with results expressed as hazard ratio (HR) with 95% confidence intervals. Results Of the 211 eligible patients, 63 (30%) had a diagnosis of sAML, compared to 148 with dnAML. Of those with sAML, 74% had antecedent MDS and 26% an MPN. Patients with sAML had an older median age (55 vs 44 years, p<0.001), more often had HCT-CI >3 (p=0.003), and more commonly had at least one cytogenetic abnormality (p=0.026). A myeloablative conditioning regimen was used in 35.3% and 66.0% of s- and dn- AML respectively. Grade II or greater acute graft-versus-host disease (GVHD) occurred in 39.7% of sAML and 29% of dnAML, with chronic GVHD reported in 60.3% and 64.5% respectively. OS at 1 year was 48.5% in sAML and 71.6% in dnAML (HR 1.93 [95%CI 1.32-2.97, p=0.0001]). Multivariate analysis accounting for disease risk index (DRI) as a co-factor identified sAML as an independent adverse risk factor for OS (HR 2.13 [95%CI 1.31-3.45], p=0.002). Compared to dnAML, sAML was associated with higher rates of disease relapse (HR 2.21 [95%CI 1.20-4.05], p=-0.011). Figure 1: Transplant outcomes (A) Overall survival dnAML vs sAML (B) Cumulative incidence of relapse at 1 year dnAML vs sAML Conclusions Patients with sAML experience poorer outcomes following allogeneic stem cell transplant than those with dnAML. Whilst the DRI stratifies AML based on cytogenetic risk and stage, our study identifies sAML as a prognostic marker independent of risk ascribed by the DRI. This has not been reported previously and if replicated, suggests the need for development of an independent prognostic model to capture the adverse risk in the sAML patient cohort. Importantly, despite poor outcomes, the lack of alternate management strategies still makes allogeneic stem cell transplant the only potential curative therapy. Figure 1 Figure 1. Disclosures Hamad: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Greenwood: Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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