Risks and outcomes of idiopathic pneumonia syndrome after nonmyeloablative and conventional conditioning regimens for allogeneic hematopoietic stem cell transplantation.

Idiopathic pneumonia syndrome (IPS) is a significant noninfectious complication of hematopoietic stem cell transplantation (HSCT). We compared the incidences and outcomes of IPS among patients who underwent allogeneic HSCT after nonmyeloablative (n = 183) compared with conventional (n = 917) conditioning between December 1997 and December 2001. Patients given nonmyeloablative conditioning were older than those given conventional conditioning (median ages, 53 vs 41 years; P =.001). The cumulative incidence of IPS was significantly lower at 120 days after nonmyeloablative conditioning than conventional conditioning (2.2% vs 8.4%; P =.003). In addition, greater patient age (older than 40 years), diagnosis of acute leukemia or myelodys-plastic syndrome, and severe acute graft-versus-host disease were associated with significantly increased risks for IPS. Among older patients (older than 40 years) given conventional conditioning, high-dose total body irradiation (TBI) was associated with an increased risk for IPS than were non-TBI-based regimens (16% vs 5.8%; P =.001). IPS occurred early after transplantation, progressed rapidly, and was associated with a high mortality rate (75%) despite aggressive support. Initiation of mechanical ventilation and the presence of renal insufficiency at IPS onset were associated with increased risks for death after IPS. These findings support the concept that lung damage from the conditioning regimen plays a crucial role in the development of IPS after HSCT.