Incidence, Risk Factors and Outcomes of Bronchiolitis Obliterans after Allogeneic Stem Cell Transplantation.

Background: Bronchiolitis obliterans (BO) after allogeneic stem cell transplantation (allo-SCT) is a late-onset, life-threatening respiratory complication which significantly reduces patients’ quality of life. Despite different therapeutic protocols, BO mortality remains high and most patients die of respiratory failure or infections. In recent practice, the source of stem cells and the conditioning regimen for allo-SCT have become more varied, but their influence on the incidence of BO is not established. Here, we retrospectively analyzed incidence of and risk factors for BO in allo-SCT protocols.

Patients and methods: Between Jan 1994 and June 2005, 2692 patients underwent allo-SCT in 14 facilities of the Kanto Study Group for Cell Therapy (KSGCT) in Japan, and 2154 surviving at least 100 days after transplantation were evaluated in this study. Clinical diagnosis of BO was made by pulmonary function tests (PFT) revealing a forced expiratory volume for 1 second (FEV1) less than 70% and FEV1/forced vital capacity less than 80% of the predicted value, along with typical changes on high-resolution computed tomography.

Results: BO developed in 57 patients with a cumulative incidence at 5 years post transplant of 2.6%. The Kaplan Meier estimate of median time interval from transplant to diagnosis of BO was 335 days (83–907). The cumulative incidence of BO at 5 years was 1.62% (12/691) in bone marrow transplants from related donors (R-BMT), 3.83% (16/424) in peripheral blood stem cell transplantation from related donors (R-PBSCT), 2.91% (24/808) in BMT from unrelated donors (UR-BMT), and 2.65% (5/199) in unrelated cord blood transplantation (CBT). The incidence of BO after R-PBSCT was significantly higher than after any other type of allo-SCT (p=0.02). At BO diagnosis, the mean value of FEV1% decreased to 52.1% from 82.2% pre-transplant. 94% of patients had already developed chronic GVHD before the onset of BO. Risk factors for BO by univariate analysis were R-PBSCT (p=0.019) and preceding chronic GVHD (p=0.000). Twenty eight patients died after developing BO, 21 of respiratory failure. Only one patient died of relapse of primary disease. Overall 5 yr-survival of patients with BO from the time of diagnosis was 46.5%, significantly less than for those without (76.2% from day 335, p=0.000) by semi-landmark analysis.

Conclusions: The incidence of BO in CBT recipients was higher than R-BMT recipients and not significantly different with UR-BMT recipients. R-PBSCT recipients who have already developed chronic GVHD have a higher risk for developing BO and need extensive care and repeated PFT examinations.