Impact of CD 34 Cell Dose and Conditioning Regimens on Donor T-Cell and Myeloid Chimerism After an Alemtuzumab-Based in-Vivo T-Cell Depleted Allogeneic Stem Cell Transplant (SCT)

evaluated the impact of different GM cut-off levels in serum and BAL on mortality. Kaplan Meier curves were used to estimate survival, and Cox proportional hazardsmodels were used to evaluate univariate and adjusted hazards ratios for 180 day all-cause mortality associated with different serum and BAL GM index cutoff values. Results: A diagnosis of probable IPA was made by a positive serumGMindex ( 0.5) alone in32patients andapositiveBAL GM index ( 0.5) alone in47patients. In 21patients, the serum andBALGMindiceswerebothpositive.Overallmortality in all patients was 52% at 180 days. Patients with a positive serum GM index at the time of IPA diagnosis had an increased mortality (60.4%; n 1⁄4 53) compared to patients with a negative serum GM index (42.6%; n 1⁄4 47). In contrast, a positive BAL GM index had no effect on mortality (Figure 1A,B). In addition, the magnitude of the serum GM index was associated with enhanced mortality. When compared to a serum GM index of 0.5, increasing values of serum GM were associated with an increased HR of 180 day mortality (serum GM 1: HR 1⁄4 2.18 (1.15-4.15); serum GM 1.5: HR 1⁄4 2.97 (1.53-5.81); serumGM 2: HR1⁄4 3.68 (1.63-8.30)). This result was confirmed in a multivariate analysis that adjusted for acute GVHD, sex, underlying hematologic disease severity, and elevated creatinine. No association was seen with increasing magnitudes of BAL GM indices. Conclusions: This study shows an increased HR for mortality with increasing cutoffs of serum GM indices, with no corresponding increase in HR with increasing BAL GM indices. We propose that the initial serum GM index value at the time of IPA diagnosis represents both an important prognostic indicator and a valuable covariate in future analyses on outcomes in HCT recipients.