High Prevalence of Abnormal Baseline Lung Function in Pediatric and Young Adult Hematopoietic Stem Cell Transplant Recipients: A Report from the TRANSPIRE Study

Background: Pulmonary complications are a major cause of morbidity and mortality in pediatric and young adult hematopoietic stem cell transplant (HSCT) recipients. The impact of preexisting lung dysfunction on posttransplant outcomes remains understudied. Methods: In a multi-institutional prospective cohort of 444 patients (≤24 years) undergoing allogeneic HSCT at eight centers, baseline lung function was categorized as normal or abnormal using clinical history, imaging, pulmonary function tests (PFTs), and pulmonologist review. Spirometry and diffusion capacity were assessed at baseline, Day 100, 1 year, and 2 years post-HSCT. Results: Baseline pulmonary dysfunction was present in 224 patients (50.4%), including impaired spirometry (46.4%), low diffusion capacity (33.8%), and imaging abnormalities (e.g., nodules 19%, interstitial changes 7.9%). These patients had significantly lower median z-scores for forced expiratory volume in 1 s (FEV1) (–2.3 vs. −0.5), forced vital capacity (FVC) (−2.0 vs. −0.3), and diffusion capacity of the lung for carbon monoxide (−2.4 vs. −0.7; all p < 0.001). Lung function impairments persisted through 2 years post-HSCT. FEV1 and FVC remained significantly lower at all time points; FEV1/FVC ratios were similar. Overall survival was lower in the abnormal group (88.4 vs. 95.9%). Seven respiratory-related deaths occurred, including acute respiratory distress syndrome (n = 3), respiratory failure (n = 2), diffuse alveolar hemorrhage (n = 1), and fibrotic lung disease (n = 1). Conclusions: Pretransplant pulmonary dysfunction is common and predicts sustained posttransplant impairment and lower survival. Comprehensive baseline assessment may aid in risk stratification and guide early interventions to improve long-term respiratory outcomes in pediatric and young adult HSCT patients. ClinicalTrials.gov identifier: NCT04098445.