Idiopathic Pneumonia Syndrome and Pulmonary Toxicity After Total Body Irradiation for Bone Marrow Transplantation in the Modern Transplant Era

Total body irradiation (TBI) is commonly used for myeloablative conditioning prior to allogeneic hematopoietic stem cell transplantation (HSCT) in high-risk, relapsed, or refractory hematologic malignancies. Pulmonary toxicity (PT)—including pneumonia, diffuse alveolar hemorrhage, and interstitial pneumonitis—is a serious complication after HSCT. Idiopathic pneumonia syndrome (IPS), defined as widespread alveolar injury without cardiogenic or infectious causes, represents a non-infectious form of PT. This study characterizes PT and IPS and explores associated factors following TBI-based HSCT in adults. We conducted a retrospective review of a prospectively collected database of adult patients treated with TBI-based HSCT from 2015 to 2022. Clinical records and chest imaging were reviewed to identify PT and IPS. IPS occurred in 20 patients (18%) of the cohort, with 8 patients (7%) within 100 days and 13 patients (13%) after 100 days. One patient experienced both early- and late-onset IPS and was counted once in the cumulative analysis. Early pulmonary infection was associated with reduced overall survival in both univariable (p = 0.002) and multivariable 100-day landmark analyses (p = 0.047). Acute graft-versus-host disease (GVHD) was independently associated with improved survival (p = 0.017), whereas chronic GVHD was not statistically significant in the landmark analyses. PT and IPS incidences were consistent with previously published adult TBI cohorts. While no significant clinical or radiation-related predictors of IPS were identified, pulmonary infection emerged as a predictor of inferior overall survival.