Lung Histology Predicts Outcome of Bronchiolitis Obliterans Syndrome after Hematopoietic Stem Cell Transplantation

Bronchiolitis obliterans (BO) is a severe complication after allogeneic hematopoietic stem cell transplantation with an unfavorable prognosis. Lung biopsy remains the gold standard for diagnosis. In this retrospective single-center study, we describe 33 patients who underwent biopsy for suspected BO. Ten patients had constrictive BO (CBO); 9 had lymphocytic bronchiolitis (LB), characterized by lymphocytic infiltration of the bronchioles. Six additional patients (4, CBO; 2, LB) had concomitant infection; 8 had other pathological diagnoses. Seven patients with CBO and 3 with LB met the National Institutes of Health consensus BO syndrome definition criteria. An additional 7 patients with histologically confirmed CBO did not meet the consensus definition, 4 of them because of concomitant airway infection. At diagnosis, there were no significant differences between the CBO and LB groups in clinical presentation; pulmonary function tests (median forced expiratory volume in one second [FEV1] at baseline, 90.4% and 99% predicted, at time of video-assisted thoracoscopic surgery, 55.1% and 60.8% for CBO and LB groups, respectively); and chest scans. Treatment was similar in both groups but outcome was different depending on histological findings. FEV1 significantly improved in LB patients compared with CBO patients. Survivals at 1 and 3 years were 77% ± 12% and 60% ± 14% for patients with CBO and 91% ± 9% for patients with LB (P = .028). Lung biopsy in patients with suspected BO enables better characterization of the pattern of BO syndrome. In contrast to CBO, LB is associated with a good long-term prognosis.