Effect of reduced‐intensity conditioning and the risk of late‐onset non‐infectious pulmonary complications in pediatric patients

Objective Late‐onset non‐infectious pulmonary complications (LONIPCs) contribute to higher morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Therefore, we investigated the risk factors of LONIPCs in pediatric patients. Method Between 2001 and 2011, 74 pediatric patients (range, 7 months to 22.7 years old; median 6.5 years old), including 29 with a primary immunodeficiency, underwent 80 allo‐HSCTs at our institution. Sixty‐seven patients who survived more than 3 months after allo‐HSCT were analyzed retrospectively. The median follow‐up period was 1 973 days (range, 126‐5 145 days). Results Nine patients (13.4%) developed LONIPCs between 90 and 3 578 days after allo‐HSCT. A myeloablative conditioning (MAC) regimen and chronic GVHD were determined as significant risk factors of LONIPCs. None of 18 patients who received the reduced‐intensity conditioning (RIC) regimen developed LONIPCs, although there was no difference in overall survival between the MAC and RIC regimen. Notably, two immunodeficient patients who received busulfan‐based MAC regimen under 2 years old developed LONIPC with no history of chronic GVHD after 5 years and 10 years from SCT, respectively, suggesting the direct toxicity of busulfan. Conclusion Our study's findings indicate that the RIC regimen reduces the risk of LONIPCs in pediatric patients.