Updated prevalence, predictors and treatment outcomes for bronchiolitis obliterans syndrome after allogeneic stem cell transplantation

Introduction: Bronchiolitis obliterans syndrome (BOS) after allogeneic haemopoietic stem cell transplant (HSCT) is an under-recognised and difficult to treat disease. This occurs in the context of limited clinical research and inconsistent diagnostic criteria. Method: Retrospective data was collected on 275 patients who underwent allogeneic HSCT at an Australian tertiary hospital between 2007 and 2017. The prevalence of BOS, defined by 2014 National Institute of Health criteria, as well as predictors for BOS and mortality were determined. Treatment outcomes, using serial spirometry, were compared between patients who received early versus late immunosuppression for BOS. Results: The prevalence of BOS was 9.1%. Myeloablative conditioning (OR: 2.7, 95%CI: 1.13–6.50, p = 0.03) and extra-pulmonary chronic graft-versus-host disease (OR 2.62, 95% CI: 1.04–6.60, p = 0.04) were associated with BOS. There was reduced median survival in the BOS group compared with the non-BOS group, but this was not statistically significant (4.1years (IQR: 2.8, 6.8) versus 4.6years (IQR: 2.4, 7.8), respectively, p = 0.33). The vast majority (87.5%) of BOS patients failed to attain improvement in FEV1 at 12 months, regardless of treatment strategy. Patients who underwent a late immunosuppression strategy had worse mean FEV1 decline compared to those who received early immunosuppression (−36.3% versus −1.6%, respectively, p = 0.03). Conclusion: BOS is a common and progressive disease following HSCT and is largely refractory to current treatment strategies. Compared to late immunosuppression, early augmentation of immunosuppression may slow lung function deterioration in the short term. However, further research is urgently needed to identify effective prevention and treatment strategies for BOS.