Noninfectious pulmonary toxicity (NPT), a significant complication of allogeneic hematopoietic cell transplantation (alloHCT), includes idiopathic pneumonia syndrome (IPS), diffuse alveolar hemorrhage (DAH), and cryptogenic organizing pneumonia (COP), with an overall incidence ranging from 1% to 15% in different case series and a variable mortality rate. A registry study of the epidemiology and outcomes of NPT after alloHCT has not been conducted to date. The primary objective of the present study was to assess the incidence of and risk factors for IPS, DAH, and COP; the secondary objective was to assess overall survival (OS) in patients developing NPT. This retrospective study included adult patients who underwent alloHCT between 2008 and 2017 and reported to the Center for International Blood and Marrow Transplant Research. Multivariable Cox proportional hazards regression models were developed to identify the risk factors for development of NPT and for OS, by including pretransplantation clinical variables and time-dependent variables of neutrophil and platelet recovery, and acute graft-versus-host disease (GVHD) post-transplantation. This study included 21,574 adult patients, with a median age of 55 years. According to the HCT Comorbidity Index (HCT-CI), 24% of the patients had moderate pulmonary comorbidity and 15% had severe pulmonary comorbidity. The cumulative incidence of NPT at 1 year was 8.1% (95% confidence interval [CI], 7.7% to 8.5%). Individually, the 1-year cumulative incidences of IPS, DAH, and COP were 4.9% (95% CI, 4.7% to 5.2%), 2.1% (95% CI, 1.9% to 2.3%), and .7% (95% CI, .6% to .8%), respectively. Multivariable analysis showed that severe pulmonary comorbidity, grade II-IV acute GVHD, mismatched unrelated donor and cord blood transplantation, and HCT-CI score ≥1 significantly increased the risk of NPT. In contrast, alloHCT performed in 2014 or later, non-total body irradiation (TBI)- and TBI-based nonmyeloablative conditioning and platelet recovery were associated with a decreased risk. In a landmark analysis at day+100 post-transplantation, the risk of DAH was significantly lower in patients who had platelet recovery by day +100. Multivariable analysis for OS demonstrated that NPT significantly increased the mortality risk (hazard ratio, 4.2; P.0001).
