Birgitta Versluijs

135 Outcome predictors in Allo-LS in children Introduction Non-infectious pulmonary complications after allogeneic hematopoietic cell transplanta- tion (HCT) causes significant morbidity and mortality. 1-5 Idiopathic pneumonia syndro- me (IPS), an early non-infectious lung disease including the spectrum of engraftment syndrome (ES) and diffuse alveolar hemorrhage (DAH), has an incidence of 2-12% and a poor prognosis, with mortality rates up to 50-80% within the first month of diagnosis. 2,6 Bronchiolitis Obliterans Syndrome (BOS) is a late onset non-infectious pulmonary com- plications following HCT. Reported incidence rate varies widely from 0-48%, depending on definition and cohort of patients. Prognosis of BOS is poor, with improvement of lung function with aggressive therapy in only 8-20% of patients 5 and mortality rates of 50- 80%. 7 In these non-infectious pulmonary complications of allogeneic HCT, immunity plays a crucial role, for which we introduced the term Allo-immune Lung Syndromes (Allo-LS). 8 We aimed to study predictors for response to Allo-LS treatment and long-term outcome in Allo-LS. Patients and methods Study design and patients We did a retrospective cohort analysis on all consecutive patients who received an allo- geneic HCT in our Center between January 2004 – December 2016. Clinical data were collected prospectively after written informed consent was acquired. Ethical committee approval of the University Medical Centre Utrecht was given (Trial numbers 05/143 and 11/063K). All patients who developed Allo-LS were included in this analysis: no restricti- ons applied. The majority of patients (81%) was described in earlier predictors analyses for developing Allo-LS. 4,8 HCT procedures Patients underwent a myeloablative conditioning: for non-malignant diseases (inborn errors of metabolism, primary immune deficiencies) the conditioning regimen consisted of targeted busulfan (AUC 90 mg*h/l in 4 days) and fludarabin (160 mg/m 2 in 4 days), in malignant disease either fractioned total body irradiation (TBI) based conditioning was given (3 x 2 x 2 Gy TBI, etoposide 60 mg/kg), or targeted busulfan (AUC 90 mg*h/l in 4 days) and fludarabin (160 mg/m 2 ), or targeted busulfan (AUC 90 mg*h/l in 4 days), fludarabin (40 mg/m 2 in 4 days) and clofarabin (120 mg/m 2 in 4 days) depending on patients age, myeloid or lymphoid origin of disease, central nervous system involvement and high risk disease characteristics. Bone marrow failure syndromes (including Fanco- ni anemia) and heavily pre-treated children with pre-existing organ failure received redu- 8