Bronchiectasis in Bronchiolitis Obliterans Syndrome after Hematopoietic Cell Transplantation.

Bronchiectasis-bronchial dilatation accompanied by impaired mucociliary clearance, chronic infection, and chronic inflammation-may contribute to poor outcomes in bronchiolitis obliterans syndrome (BOS) complicating hematopoietic cell transplantation, though its epidemiology and impact are poorly understood. We assessed factors associated with bronchiectasis in BOS. We also assessed relationships between bronchiectasis and survival, respiratory infections, and percent predicted forced expiratory volume in one second (FEV1%). This single-center retrospective cohort study included adults who underwent allogeneic hematopoietic cell transplantation from 2010 to 2023 and who subsequently developed BOS. Bronchiectasis is defined based on validated radiographic and clinical criteria. We used multivariable logistic and linear regression, extended Cox regression models, negative binomial regression, and generalized estimating equations to determine relationships between pre-BOS events and subsequent bronchiectasis, and between bronchiectasis and death, infections, and FEV1%. Among the 87 patients included for analysis, 54% developed bronchiectasis over a median follow-up of 2.2 yr (interquartile range, 1.0 to 5.8) after BOS diagnosis. Thirty-three patients (37.9%) died. None of the prespecified risk factors were associated with bronchiectasis. Bronchiectasis was associated with an increased risk of death (HR, 3.10; 95% CI, 1.40 to 6.48; P = .0048) and an increased incidence rate of respiratory infections (IRR, 1.93; 95% CI, 1.23 to 3.02; P = .0040), controlling for confounders. Among those with bronchiectasis, chronic infection with Pseudomonas aeruginosa occurred in 8 (17.0%) and nontuberculous mycobacteria in 11 (23.4%). FEV1% was lower and declined more rapidly in those with bronchiectasis. Bronchiectasis frequently accompanies BOS and is associated with 2 poorer outcomes, though its causes in this population are not known.