Comparison of Outcomes After Allogeneic HSCT for Adult Patients with AML in Remission Using in the Conditioning Regimen Either I.V. Busulfex (BU) Plus Cyclophosphamide (Cy) or TBI Plus Cy: An- ALWP-EBMT Survey.

Abstract 195

TBI/CY and oral (p.o) Bu/Cy are the traditional allogeneic HSCT (alloHSCT) myeloablative conditioning regimens for adults with AML with comparable survival and relapse probabilities. Intravenous (i.v.) Bu in contrast to p.o Bu has more predictable pharmacokinetics and a more favorable toxicity profile. Post transplantation outcomes with i.v. Bu/Cy, thus, may be superior to those achieved with TBI/Cy. In order to address these issues, the ALWP of the EBMT performed a survey comparing i.v. Bu/Cy to TBI/Cy as conditioning regimen for adult pts. with AML undergoing alloHSCT. Overall, 603 alloHSCT were analyzed. One hundred pts. underwent alloHSCT with Bu/Cy while 503 with TBI/Cy. Age was 41 (range, 18–57) and 41 (range, 16–61) years and median transplant year was 2004 (2000 – 2005) and 2003 (2000 – 2005) for the Bu/Cy and TBI/Cy groups, respectively. Disease status at alloHSCT were CR1 – 81% vs. 78% and CR2–19% vs. 22% for the Bu/Cy and TBI/Cy groups, respectively. WBC count at diagnosis was 11×109/L and 15×109/L, respectively. Regarding the cytogenetic classification, 10% and 10% were good, 60% and 55% were intermediate and 9% and 6% were poor risk, respectively (data were NA for 21%–26% of pts). Sixty nine percent and 68% of both groups underwent alloHSCT from sibling donors, while 31% and 32% from MUD, respectively. Length of follow up was 37(15–86) and 57 (1–105) months for both groups, respectively. Sixty nine percent and only 41% of the Bu/Cy and TBI/Cy groups received PB, while 31% and 59% received BM grafts, respectively (p<0.0001). Engraftment was similar in the Bu/Cy vs. the TBI/Cy groups, 95% and 96%, respectively. Cumulative incidence of TRM at 2y was 17+4% and 23+2%, respectively (p=0.23). Acute GVHD (II–IV) was also similar between the 2 groups, 28% and 32%, respectively. Two year relapse incidence was 30+5% and 22+2% for Bu/Cy vs. TBI/Cy, respectively (p=0.03) while LFS was comparable 57+5% and 61+2%, respectively (p=0.5). In multivariate analysis Cy/TBI was found to be an independent good prognostic factor for reduce relapse rate (p=0.03, HR-1.67) and there was a trend for higher TRM (p=0.16). Poor prognostic factors for LFS and TRM were age >40y, disease status (CR2 vs. CR1) and MUD vs. Sib. donor. In conclusion, in this retrospective EBMT survey outcomes of alloHSCT in adult pts. with AML in CR using either i.v Bu/Cy or TBI/Cy were comparable.