Prospective Evaluation of the Efficacy of Budesonide/Formoterol in Bronchiolitis Obliterans in AHSCT

Inclusion Criteria: * Age ≥16 years. * Previous normal PFTs available. * Absence of extrathoracic GVH disease justifying initiation or intensification of systemic immunosuppressive therapy. * Respiratory signs present for less than 6 months. * AHSCT recipients who have developed moderate to severe bronchiolitis obliterans, defined by reduction of FEV1/VC below the 5th percentile of predicted normal or \< 80% of predicted, with FEV1 \< 80% of predicted and ≥ 40% of predicted, not reversible after inhalation of short-acting beta-2 agonist. AHSCT recipients with FEV1 \< 80% of predicted and ≥ 40% of predicted, not reversible after inhalation of short-acting beta-2 agonist and TLC ≥ 80% of predicted. * Respiratory symptoms related to obstructive lung disease present for at least 6 months. * Negative respiratory microbiology work-up. * Informed consent signed by the patient or both parents of a minor. Exclusion Criteria: * Extrathoracic graft versus host reaction justifying initiation or intensification of systemic immunosuppressive therapy. * Use of inhaled bronchodilator and/or corticosteroid therapy at the time of inclusion. * Known intolerance to inhaled bronchodilators and/or corticosteroids and/or lactose. * Personal or donor history of asthma. * Active smoking * FEV1 \< 40% of predicted normal or ≥ 80% of predicted normal or PO2 \< 50 mmHg. * Documented respiratory tract infection. * Pregnancy. * Absence of effective contraception during the trial. * Not covered by French national health insurance.