G. Lucchini on behalf of the EBMT PDWP SCT in pediatric AML in 1CR: does the conditioning regimen matter? Scientific Day 12 th May, 2016 London

Conditioning in AML TBI vs Bu-based based conditioning with Cy addition (Thomas Blood 1977; Santos NEJM 1983) CR1, children, post 2000: De Berranger 2014, Ishida 2015 no differences, Copeland 2013 Leukemia free survival Overall survival

Bu-Cy-Mel in pediatric AML AML 2002/01 AIEOP study CR1 Locatelli, BMT pts 75% oral Bu 25% iv Bu 91% Bu levels (AUC ng/ml) aGvHD grade II/IV= 38% cGvHD = 25% TRM = 7% RI = 17% DFS/OS = 8 yrs Strahm et al, 2011 = TRM 33% in children >12 yrs with MDS Interfant study amended because of increased TRM

EBMT DATA: what are we doing? Retrospective, registry study Inclusion criteria: Children >2 and <18 years of age 1 SCT for AML in CR At least 2 years follow up Exclusion criteria: Mismatched donor Cord blood as stem cell source Endpoints: 5yrs LFS/OS per conditioning regimen Relapse incidence, non-relapse mortality incidence

631 patients from 204 centres

Busulfan administration Oral administration was significantly more frequent in patients receiving BuCyMel as compared to those receiving BuCy conditioning (85.5% vs 44.5%, p <0.001).

631 patients from 204 centres VariablesStatistics TBICy (=109) BuCy (=389) BuCyMel (=133) Total (=631) Pval (95%CI) Age at HSCT Median Range 14.8 ( ) 11.7 (2-18) 9.8 ( ) 11.9 (2-18) Year of HSCTMedian Diagnosis to HSCT Median Range 4.7 (2-20.5) 4.8 ( ) 5.3 ( ) 4.9 ( ) Patient sexMale64 (58.7%)206 (53%)79 (59.4%)349 (55.3%)1 Donor type MSD MUD 74 (67.9%) 35 (32.1%) 302 (77.6%) 87 (22.4%) 82 (61.7%) 51 (38.3%) 458 (72.6%) 173 (27.4%) In vivo T cell depletion Yes29 (26.6%)67 (17.2%)42 (31.6%)138 (21.9%)0.127 Stem cell source BM PB 82 (75.2%) 27 (24.8%) 250 (64.3%) 139 (35.7%) 108 (81.2%) 25 (18.8%) 440 (69.7%) 191 (30.3%) Cytogenetics/molecular risk stratification not available Cytogenetics remission status was available for 190 pts and remissions were equally distributed in the 3 groups (88.2% vs 89.8% vs 92.9%, p=1) Frontline protocols: more than 10 with different criteria for SCT in CR1

VariablesStatistics TBICy (=109) BuCy (=389) BuCyMel (=133) Total (=631) Pval (95%CI) Engraftment % CI 95% 100 ( ) 97.9 ( ) 98.4 ( ) 98.4 ( ) aGVHD grade ≥ II % CI 95% 31.1 ( ) 29.3 ( ) 42.7 ( ) 32.5 ( ) aGVHD grade ≥ III % CI 95% 6.8 ( ) 9.6 ( ) 17.6 ( ) 10.8 ( ) cGVHD % CI 95% 27.8 ( ) 25.8 ( ) 35.2 ( ) 27.5 ( ) 1 5yrs-Non relapse mortaliy % CI 95% 8.1 ( ) 10.5 ( ) 10.8 ( ) 10.1 ( ) 0.79 Results I 1 case of VOD related death (BuCyMel) 1 case of idiopathic pneumonia related death (BuCy) Pt >10 yrs had an increased NRM (13.1% vs 5.7%, p<0.01)

CI Relapse TBI Cy = 30% Bu Cy = 31.5% BuCyMel = 14.7% Leukemia free survival TBI Cy = 61.9% Bu Cy = 58% BuCyMel = 74.5% Overall survival TBI Cy = 64.5% Bu Cy = 64% BuCyMel = 76.6%

Multivariate analysis RINRMLFSOS BuCyMel0.44 ( ) p< ( ) p= Age HSCT >10 yrs ( ) p< Time from dx to HSCT (>1 yr) ( ) p< aGVHD ( ) p< Stem cell source PB vs BM ( ) p= ( ) p= ( ) p< 0.01 Year of HSCT

Conclusions Our data confirm no difference between BuCy and TBI based regimen for the treatment of AML CR1 BuCyMel proved better than any other conditioning regimen in reducing the risk of relapse BuCyMel was well tolerated (specifically in pts<10 yrs) LFS/OS was significantly higher in BuCyMel treated pts Future directions Expand the analysis to pts with advanced disease at SCT and document if BuCyMel is of any benefit in that context BuCyMel is still used in the context of diseases with poor prognosis as JMML, so similar data might be reassuring at least in terms of safety and further studies are warranted to understand its impact.

Acknowledgments: 204 participating centres EBMT PDWP: Peter Bader, Chair Eric Behou, Statistician Arnauld Dalissier, Data Manager GOSH, London: Paul Veys Persis Amrolia Kanchan Rao Robert Chiesa Juliana Silva Sujith Samarasinghe, GOSH Rachel Hough, UCLH Myriam Labopin, EBMT Statistician