The Modulating Effect of Azacitidine (Aza C) on the Cytogenetically Tracked MDS Clone Impact Survival.

MDS is a clonal hematopoietic stem cell disorder characterized by progressive bone marrow failure leading to death from infections and bleeding in the majority of patients. Transformation to acute leukemia occurs in 35-40%. Most treatments, other than allogeneic SCT, have been ineffective. Treatment with Aza C has been shown to be clinically effective and alters the natural history of disease (Silverman et al JCO 2002). We have previously demonstrated Aza C modulation of the MDS clone and established five different cytogenetic categories based on its modulating effect (Najfeld et al, ASH 2002). The goal of this extended study was to determine biological and clinical consequences of Aza C modulation on the five cytogenetic categories. Among 224 patients treated with AzaC, multiple sequential studies were performed in187 pts, while 41 pts without follow up studies, were excluded from this report. The initial karyotype prior to therapy with Aza C was normal in 99 pts (53%) and abnormal in 88 pts (47%). These latter patients were not further subdivided into good, intermediate or poor risk according to IPSS. The table below shows the Kaplan Meier median survival of the 5 subcategories based on the modulating effects of Aza C on the cytogenetically identified MDS clone.

When survival was compared between cytogenetic subgroups there was a statistical difference between some groups. Survival of patients with normal cytogenetics (group 1) was superior when compared to either group 3 (p=.0001) or group 4 (p=.00015). Even for pts who developed an abnormal clone while on AzaC (group 2) survival was significantly longer when compared to either group 3 (p=0004) or group 4 (p=00001). Moreover, prognostic significance was observed for pts who initially had an abnormal karyotype that was diminished or eradicated on AZA C therapy (group 5) when compared to groups 3 (p=0.009) and 4 (p-0.0006). The emergence of a cytogenetically abnormal clone while on treatment with Aza C is not associated with shortened survival compared to those who remain cytogenetically normal. Response to Aza C can occur even with the persistence of the MDS clone or with the emergence of a new clone. This suggest that AZA C can modulate the responsivness of MDS hematopoietic progenitors. Our findings demonstrate that AZA C modulation of the cytogenetically marked MDS clone is associated with distinct subgroups with differing survival characteristics.