Pulmonary Complications in Pediatric and Adolescent Patients Following Allogeneic Hematopoietic Cell Transplantation

The Pathology of Pulmonary Disease After Pediatric Hematopoietic Stem Cell Transplantation

Pulmonary complications continue to cause significant morbidity and mortality in posthematopoietic stem cell transplantation (HSCT) settings. The histopathology of pulmonary diseases in the post-HSCT context is poorly characterized, especially in the pediatric population. We sought to characterize the pathologic spectrum of pulmonary disease post-HSCT in a pediatric cohort. Fifty-six specimens, including 53 biopsy specimens, corresponding to 53 patients, were identified. Biopsy slides were reviewed and assigned to diagnostic categories (infectious, graft-versus-host disease, vasculopathy, indeterminate, and others) by consensus among 3 pediatric pulmonary pathologists, taking into consideration pathologic, clinical, radiologic, and laboratory findings. The most common diagnostic category was infection (n=20). Vasculopathy, mostly in the form of fibromyxoid intimal expansion, was very common in the entire cohort (n=26) and was the sole finding in a small subset of patients (n=5), with particularly poor outcomes. A subset of biopsies remained indeterminate (n=10), and the findings in this cohort were dominated by acute lung injury. The latter group had a poor prognosis, with a short biopsy-to-death interval. The overall clinicopathologic concordance was 40%, most commonly agreeing in the infectious category. Finally, wedge biopsies led to a change in management in 69% of cases versus 23% of limited procedures (i.e., core needle biopsies). Our results suggest that while infectious complications continue to be common post-HSCT, other findings such as vasculopathy and acute lung injury portend a particularly poor prognosis and should be actively sought and reported.

Epidemiology of Diffuse Alveolar Hemorrhage in Pediatric Allogeneic Hematopoietic Cell Transplantation Recipients

Diffuse alveolar hemorrhage (DAH) is a life-threatening pulmonary toxicity that can arise after hematopoietic cell transplantation (HCT). Risk factors and outcomes are not well understood owing to a sparsity of cases spread across multiple centers. The objectives of this epidemiologic study were to characterize the incidence, outcomes, transplantation-related risk factors and comorbid critical care diagnoses associated with post-HCT DAH. Retrospective analysis was performed in a multicenter cohort of 6995 patients age ≤21 years who underwent allogeneic HCT between 2008 and 2014 identified through the Center for International Blood and Marrow Transplant Research registry and cross-matched with the Virtual Pediatric Systems database to obtain critical care characteristics. A multivariable Cox proportional hazard model was used to determine risk factors for DAH. Logistic regression models were used to determine critical care diagnoses associated with DAH. Survival outcomes were analyzed using both a landmark approach and Cox regression, with DAH as a time-varying covariate. DAH occurred in 81 patients at a median of 54 days post-HCT (interquartile range, 23 to 160 days), with a 1-year post-transplantation cumulative incidence probability of 1.0% (95% confidence interval [CI], .81% to 1.3%) and was noted in 7.6% of all pediatric intensive care unit patients. Risk factors included receipt of transplantation for nonmalignant hematologic disease (reference: malignant hematologic disease; hazard ratio [HR], 1.98; 95% CI, 1.22 to 3.22; P = .006), use of a calcineurin inhibitor (CNI) plus mycophenolate mofetil (MMF) as graft-versus-host disease (GVHD) prophylaxis (referent: CNI plus methotrexate; HR, 1.89; 95% CI, 1.07 to 3.34; P = .029), and grade III-IV acute GVHD (HR, 2.67; 95% CI, 1.53-4.66; P < .001). Critical care admitted patients with DAH had significantly higher rates of systemic hypertension, pulmonary hypertension, pericardial disease, renal failure, and bacterial/viral/fungal infections (P < .05) than those without DAH. From the time of DAH, median survival was 2.2 months, and 1-year overall survival was 26% (95% CI, 17% to 36%). Among all HCT recipients, the development of DAH when considered was associated with a 7-fold increase in unadjusted all-cause post-HCT mortality (HR, 6.96; 95% CI, 5.42 to 8.94; P < .001). In a landmark analysis of patients alive at 2 months post-HCT, patients who developed DAH had a 1-year overall survival of 33% (95% CI, 18% to 49%), compared to 82% (95% CI, 81% to 83%) for patients without DAH (P < .001). Although DAH is rare, it is associated with high mortality in the post-HCT setting. Our data suggest that clinicians should have a heightened index of suspicion of DAH in patients with pulmonary symptoms in the context of nonmalignant hematologic indication for HCT, use of CNI + MMF as GVHD prophylaxis, and severe acute GVHD. Further investigations and validation of modifiable risk factors are warranted given poor outcomes.

A Japanese retrospective study of non-tuberculous mycobacterial infection in children, adolescents, and young adult patients with hematologic-oncologic diseases

Non-tuberculous mycobacterial infection (NTM) is rare in healthy children, with lymphadenitis being the most common presentation. Immunocompromised populations are known to be at high risk, but the clinical picture of NTM infection in pediatric hematology/oncology patients is unclear. In this nationwide retrospective analysis of patients under the age of 40 treated in Japanese pediatric hematology/oncology departments who developed NTM infection between January 2010 and December 2020, 36 patients were identified: 21 patients with hematopoietic stem cell transplantation (HSCT) and 15 non-transplant patients. Post-transplant patients were infected with NTM at 24 sites, including the lungs (N=12), skin and soft tissues (N=6), bloodstream (N=4), and others (N=2). Nine of 12 patients with pulmonary NTM infection had a history of pulmonary graft-versus-host disease (GvHD), and rapid-growing mycobacteria (RGM) were isolated from 5 of them. In non-transplant patients, the primary diseases were acute lymphoblastic leukemia (ALL; N=5), inborn errors of immunity (IEI; N=6), and others (N=4). All cases of ALL had bloodstream infections with RGM, whereas all cases of IEI were infected with slow-growing mycobacteria (SGM). In summary, 3 typical clinical scenarios for pediatric hematology/oncology patients have been established: RGM-induced pulmonary disease in patients with pulmonary GvHD, RGM bloodstream infection in patients with ALL, and SGM infection in patients with IEI. Our findings suggest that NTM must be regarded as a pathogen for infections in these high-risk patients, especially those with pulmonary GvHD, who may require active screening for NTM.

Lung infections in immunocompromised children

Pulmonary infection is the leading cause of infectious morbidity and mortality in children with immune defects. We provide a comprehensive review of lung infections in immunocompromised children, with a focus on imaging findings and imaging-based management. We include an overview of the immune defences of the respiratory tract, the aetiologies of immune defects in children, the features of specific infections and important differential diagnoses and describe diagnostic strategies using imaging and non-imaging-based techniques.

Intensive care risk and long-term outcomes in pediatric allogeneic hematopoietic cell transplant recipients

ABSTRACT

Allogeneic hematopoietic cell transplantation (HCT) can be complicated by life-threatening organ toxicity and infection necessitating intensive care. Epidemiologic data have been limited by single-center studies, poor database granularity, and a lack of long-term survivors. To identify contemporary trends in intensive care unit (ICU) use and long-term outcomes, we merged data from the Center for International Blood and Marrow Transplant Research and the Virtual Pediatric Systems databases. We identified 6995 pediatric patients with HCT aged ≤21 years who underwent first allogeneic HCT between 2008 and 2014 across 69 centers in the United States or Canada and followed patients until the year 2020. ICU admission was required for 1067 patients (8.3% by day +100, 12.8% by 1 year, and 15.3% by 5 years after HCT), and was linked to demographic background, pretransplant organ toxicity, allograft type and HLA-match, and the development of graft-versus-host disease or malignancy relapse. Survival to ICU discharge was 85.7%, but more than half of ICU survivors required ICU readmission, leading to 52.5% and 42.6% survival at 1- and 5-years post-ICU transfer, respectively. ICU survival was worse among patients with malignant disease, poor pretransplant organ function, and alloreactivity risk factors. Among 1-year HCT survivors, those who required ICU in the first year had 10% lower survival at 5 years and developed new dialysis-dependent renal failure at a greater rate (P<.001). Thus, although ICU management is common and survival to ICU discharge is high, ongoing complications necessitate recurrent ICU admission and lead to a poor 1-year outcome in select patients who are at high risk.

Pulmonary microbiome and transcriptome signatures reveal distinct pathobiologic states associated with mortality in two cohorts of pediatric stem cell transplant patients

Lung injury is a major determinant of survival after pediatric hematopoietic cell transplantation (HCT). A deeper understanding of the relationship between pulmonary microbes, immunity, and the lung epithelium is needed to improve outcomes. In this multicenter study, we collected 278 bronchoalveolar lavage (BAL) samples from 229 patients treated at 32 children's hospitals between 2014-2022. Using paired metatranscriptomes and human gene expression data, we identified 4 patient clusters with varying BAL composition. Among those requiring respiratory support prior to sampling, in-hospital mortality varied from 22-60% depending on the cluster (p=0.007). The most common patient subtype, Cluster 1, showed a moderate quantity and high diversity of commensal microbes with robust metabolic activity, low rates of infection, gene expression indicating alveolar macrophage predominance, and low mortality. The second most common cluster showed a very high burden of airway microbes, gene expression enriched for neutrophil signaling, frequent bacterial infections, and moderate mortality. Cluster 3 showed significant depletion of commensal microbes, a loss of biodiversity, gene expression indicative of fibroproliferative pathways, increased viral and fungal pathogens, and high mortality. Finally, Cluster 4 showed profound microbiome depletion with enrichment of Staphylococci and viruses, gene expression driven by lymphocyte activation and cellular injury, and the highest mortality. BAL clusters were modeled with a random forest classifier and reproduced in a geographically distinct validation cohort of 57 patients from The Netherlands, recapitulating similar cluster-based mortality differences (p=0.022). Degree of antibiotic exposure was strongly associated with depletion of BAL microbes and enrichment of fungi. Potential pathogens were parsed from all detected microbes by analyzing each BAL microbe relative to the overall microbiome composition, which yielded increased sensitivity for numerous previously occult pathogens. These findings support personalized interpretation of the pulmonary microenvironment in pediatric HCT, which may facilitate biology-targeted interventions to improve outcomes.

Complications of Cancer Therapy in Children: A Comprehensive Review of Body Imaging Findings

ABSTRACT

Complications of cancer therapy in children can result in a spectrum of toxicities that can affect any organ system and result in a range of morbidity. Complications may occur at the initiation of therapy or years following treatment. Although childhood cancer remains rare, increasing survival rates means more children are living longer following their treatment. Radiologists often play an important role in the diagnosis and evaluation of these complications, and thus, awareness of their imaging findings is essential to guide management and avoid misdiagnosis. This second part of a 2-part review aims to illustrate the typical body imaging findings of cancer therapy-related toxicities, including both early and late treatment effects. The article also discusses the differential diagnosis of imaging findings, highlighting pearls and pitfalls in making the appropriate diagnosis.

Critical Illness Risk and Long-Term Outcomes Following Intensive Care in Pediatric Hematopoietic Cell Transplant Recipients

Background

Allogeneic hematopoietic cell transplantation (HCT) can be complicated by the development of organ toxicity and infection necessitating intensive care. Risk factors for intensive care admission are unclear due to heterogeneity across centers, and long-term outcome data after intensive care are sparse due to a historical paucity of survivors.

Methods

The Center for International Blood and Marrow Transplant Research (CIBMTR) was queried to identify patients age ≤21 years who underwent a 1st allogeneic HCT between 2008-2014 in the United States or Canada. Records were cross-referenced with the Virtual Pediatric Systems pediatric ICU database to identify intensive care admissions. CIBMTR follow-up data were collected through the year 2020.

Result

We identified 6,995 pediatric HCT patients from 69 HCT centers, of whom 1,067 required post-HCT intensive care. The cumulative incidence of PICU admission was 8.3% at day +100, 12.8% at 1 year, and 15.3% at 5 years post HCT. PICU admission was linked to younger age, lower median zip code income, Black or multiracial background, pre-transplant organ toxicity, pre-transplant CMV seropositivity, use of umbilical cord blood and/or HLA-mismatched allografts, and the development of post-HCT graft-versus-host disease or malignancy relapse. Among PICU patients, survival to ICU discharge was 85.7% but more than half of ICU survivors were readmitted to a PICU during the study interval. Overall survival from the time of 1st PICU admission was 52.5% at 1 year and 42.6% at 5 years. Long-term post-ICU survival was worse among patients with malignant disease (particularly if relapsed), as well as those with poor pre-transplant organ function and alloreactivity risk-factors. In a landmark analysis of all 1-year HCT survivors, those who required intensive care in the first year had 10% lower survival at 5 years (77.1% vs. 87.0%, p<0.001) and developed new dialysis-dependent renal failure at a greater rate (p<0.001).

Conclusions

Intensive care management is common in pediatric HCT patients. Survival to ICU discharge is high, but ongoing complications necessitate recurrent ICU admission and lead to a poor 1-year outcome in many patients. Together, these data suggest an ongoing burden of toxicity in pediatric HCT patients that continues to limit long-term survival.

Diffuse alveolar hemorrhage after hematopoietic cell transplantation- response to treatments and risk factors for mortality

Diffuse alveolar hemorrhage (DAH) is a life-threatening complication of hematopoietic cellular therapy (HCT). This study aimed to evaluate the effect of DAH treatments on outcomes using data from consecutive HCT patients clinically diagnosed with DAH from 3 institutions between January 2018-August 2022. Endpoints included sustained complete response (sCR) defined as bleeding cessation without recurrent bleeding, and non-relapse mortality (NRM). Forty children developed DAH at a median of 56.5 days post-HCT (range 1-760). Thirty-five (88%) had at least one concurrent endothelial disorder, including transplant-associated thrombotic microangiopathy (n=30), sinusoidal obstructive syndrome (n=19), or acute graft versus host disease (n=10). Fifty percent had a concurrent pulmonary infection at the time of DAH. Common treatments included steroids (n=17, 25% sCR), inhaled tranexamic acid (INH TXA,n=26, 48% sCR), and inhaled recombinant activated factor VII (INH fVIIa, n=10, 73% sCR). NRM was 56% 100 days after first pulmonary bleed and 70% at 1 year. Steroid treatment was associated with increased risk of NRM (HR 2.25 95% CI 1.07-4.71, p=0.03), while treatment with INH TXA (HR 0.43, 95% CI 0.19- 0.96, p=0.04) and INH fVIIa (HR 0.22, 95% CI 0.07-0.62, p=0.005) were associated with decreased risk of NRM. Prospective studies are warranted to validate these findings.

Pulmonary Histopathologic Findings in Pediatric Patients After Hematopoietic Stem Cell Transplantation: An Autopsy Study

BACKGROUND

Pathologic characterization of pulmonary complications following hematopoietic stem cell transplantation (HSCT) is limited. We describe lung findings in pediatric patients who died following HSCT and attempt to identify potential clinical associations.

METHODS

Pathology databases at Texas Children's Hospital and the Children's Hospital of Philadelphia were queried (2013-2018 CHOP and 2017-2018 TCH). Electronic medical records and slides were reviewed.

RESULTS

Among 29 patients, 19 received HSCT for hematologic malignancy, 8 for non-malignant hematologic disorders, and 2 for metastatic solid tumors. Twenty-five patients (86%) showed 1 or more patterns of acute and organizing lung injury. Sixty-two percent had microvascular sclerosis, with venous involvement noted in most cases and not correlating with clinical history of pulmonary hypertension, clinical transplant-associated thrombotic microangiopathy, irradiation, or graft-versus-host disease. Features suggestive of graft-versus-host-disease were uncommon: 6 patients had lymphocytic bronchiolitis, and only 2 patients had evidence of bronchiolitis obliterans (both clinically unexpected), both with a mismatched unrelated donor transplant.

CONCLUSIONS

Acute and subacute alveolar injury (diffuse alveolar damage or organizing pneumonia) is common in pediatric patients who died following HSCT and is difficult to assign to a specific etiology. Microvascular sclerosis was frequent and did not correlate with a single distinct clinical feature.

Defibrotide modulates pulmonary endothelial cell activation and protects against lung inflammation in pre-clinical models of LPS-induced lung injury and idiopathic pneumonia syndrome

Introduction

A multiple organ dysfunction syndrome (MODS) workshop convened by the National Institute of Child Health and Human Development in 2015 identified acute respiratory distress syndrome (ARDS) and complications of allogeneic blood and marrow transplantation (allo-BMT) as contributors to MODS in pediatric patients. Pulmonary dysfunction also remains a significant complication of allo-BMT. Idiopathic pneumonia syndrome (IPS) defines non-infectious, acute, lung injury that occurs post-transplant. Injury and activation to endothelial cells (ECs) contribute to each form of lung inflammation.

Methods

Two murine models were employed. In an ARDS model, naïve B6 mice receive an intravenous (i.v.) injection of lipopolysaccharide (LPS). In the established model of IPS, naïve B6D2F1 mice receive lethal total body irradiation followed by BMT from either allogeneic (B6) or syngeneic (B6D2F1) donors. Lung inflammation was subsequently assessed in each scenario.

Results

Intravenous injection of LPS to B6 mice resulted in enhanced mRNA expression of TNFα, IL-6, Ang-2, E-, and P-selectin in whole lung homogenates. The expression of Ang-2 in this context is regulated in part by TNFα. Additionally, EC activation was associated with increased total protein and cellularity in broncho-alveolar lavage fluid (BALF). Similar findings were noted during the development of experimental IPS. We hypothesized that interventions maintaining EC integrity would reduce the severity of ARDS and IPS. Defibrotide (DF) is FDA approved for the treatment of BMT patients with sinusoidal obstruction syndrome and renal or pulmonary dysfunction. DF stabilizes activated ECs and protect them from further injury. Intravenous administration of DF before and after LPS injection significantly reduced mRNA expression of TNFα, IL6, Ang-2, E-, and P-selectin compared to controls. BALF showed decreased cellularity, reflecting less EC damage and leak. Allogeneic BMT mice were treated from day -1 through day 14 with DF intraperitoneally, and lungs were harvested at 3 weeks. Compared to controls, DF treatment reduced mRNA expression of TNFα, IL6, Ang-2, E-, and P- selectin, BALF cellularity, and lung histopathology.

Conclusion

The administration of DF modulates EC injury in models of ARDS and IPS. Cytokine inhibition in combination with agents that stabilize EC integrity may be an attractive strategy for patients in each setting.

Case report: Irinotecan-induced interstitial lung disease in an advanced colorectal cancer patient resurfacing decades after allogeneic bone marrow transplantation for aplastic anemia; a case report and narrative review of literature

Two mechanisms of drug-induced interstitial lung disease (DILD) have been reported: 1) direct injury of lung epithelial cells and/or endothelial cells in lung capillaries by the drug and/or its metabolites and 2) hypersensitivity reactions. In both mechanisms, immune reactions such as cytokine and T cell activation are involved in DILD. While past and present lung diseases and accumulative lung damage due to smoking and radiation are risk factors for DILD, the association between the immune status of the host and DILD is not well known. Herein, we report a case of advanced colorectal cancer with a history of allogeneic bone marrow transplantation for aplastic anemia more than 30 years prior, in which DILD occurred early after irinotecan-containing chemotherapy. Bone marrow transplantation might be a potential risk factor for DILD.

Evaluation of Children with Malignancies for Blood and Marrow Transplantation: A Report from the ASTCT Committee on Practice Guidelines

Evaluation of a candidate for hematopoietic cell transplantation (HCT) is a complex process with substantial intercenter variability. Although literature providing guidance for evaluating the eligibility of adults is well established, similar guidance for children is lacking. To address gaps between adult recommendations and the specific needs of children, we convened a panel of pediatric HCT experts from a wide geographic range of American Society of Transplantation and Cellular Therapy (ASTCT) member institutions to offer recommendations for pediatric-focused pre-HCT evaluation. In this report from the ASTCT Committee on Practice Guidelines, we present a practical framework for evaluating children with malignancies who are candidates for HCT. We also highlight key differences from adults and emphasize areas of unmet need that require additional research to delineate best practices.

High-Dose Busulfan-Fludarabine Conditioning and Low Alveolar Volume as Predictors of Pulmonary Complications after Allogeneic Peripheral Blood Stem Cell Transplantation in Children

This study was conducted to investigate risk factors and predictors of infectious and noninfectious pulmonary complications (PCs) after allogeneic hematopoietic stem cell transplantation in children. We conducted a retrospective analysis of the post-transplantation PCs of 240 patients who underwent allogeneic peripheral blood stem cell transplantation (allo-PBSCT) between 2009 and 2018. Transplantation-related variables, pretransplantation baseline spirometry, body plethysmography, and CO diffusing capacity were analyzed for association with the development of infectious PCs (IPCs) and noninfectious PCs (NIPCs). Compared with the control group, the PC group had statistically significantly lower overall survival (50.6% versus 77.8%; P < .001), higher disease-related mortality (26.6% versus 54.4%; P < .001), and higher nonrelapse mortality (31.6% versus 5.9%; P < .001). A greater number of patients received pretransplantation conditioning with high-dose busulfan (520 mg/m²; Bu 520) and fludarabine (160 mg/m²; Flu 160) in both the IPC and NIPC groups. In the multivariate Cox hazard regression analysis, Bu 520 significantly increased the risk of NIPCs (hazard ratio [HR], 1.99; 95% confidence interval [CI], 1.13 to 3.49; P = .016), and Flu 160 was a predictor of IPCs (HR, 1.99; 95% CI, 1.13 to 3.49; P = .016). The Bu 520 + Flu 160 regimen was associated with a statistically significant increase in the risk of NIPC (HR, 1.92; 95% CI, 1.09 to 3.37; P = .023). In a multivariate analysis using pretransplantation baseline lung function, alveolar volume (VA) grades 3 and 4 and lung function score (LFS) VA categories III and IV were associated with increased risk for both IPCs and NIPCs. Our data identify receipt of the high-dose Bu-Flu conditioning regimen as an independent risk factor for NIPCs after allo-PBSCT. Impaired CO diffusing capacity before transplantation, especially VA reduction, contributes to the risk of post-transplantation pulmonary complications, and pretransplantation risk can be estimated by grading the degree of insufficiency of VA and LFS VA.

Late pulmonary complications related to cancer treatment in children

As the number of childhood cancer survivors increases, a heightened awareness and recognition of therapy-related late effects is becoming more important. Pulmonary complications are the third leading cause of late mortality in cancer survivors. Diagnosis of these complications on chest imaging helps facilitate prompt treatment to mitigate adverse outcomes. In this review, we summarize the imaging of late pulmonary complications of cancer therapy in children and highlight characteristic findings that should be recognized by radiologists.

Noninvasive Ventilation Exposure Prior to Intubation in Pediatric Hematopoietic Cell Transplant Recipients

BACKGROUND

Noninvasive ventilation (NIV) has become more studied in immunocompromised patients. However, it has not been studied in hematopoietic cell transplantation (HCT) recipients, who have higher mortality and higher pulmonary complication rates than other immunocompromised patients. This population may be prone to negative effects from this treatment modality. The aim of this study was to determine whether NIV use is associated with worse outcomes in this vulnerable patient population.

METHODS

A secondary analysis of a retrospective multi-center database was performed. Twelve pediatric ICUs across the United States enrolled HCT subjects from 2009-2014 that were admitted to the pediatric ICU (PICU) with the diagnosis of acute respiratory failure. Subjects exposed to NIV prior to intubation were compared against those not exposed to NIV. Our primary outcome was all-cause mortality at 90 d; secondary outcomes included ventilator-free days (VFD) at 28 d and development of pediatric ARDS. Multivariable logistic and linear regression models were constructed using variables significant on univariable analysis.

RESULTS

Two-hundred eleven subjects were included. Of these, 82 (39%) received NIV prior to intubation. Those that received NIV prior to intubation were older (13 vs 6 y, P < .001) and more commonly diagnosed with respiratory distress (90% vs 74%, P = .004). On multivariable analysis, NIV use prior to intubation was associated with a higher PICU mortality (hazard ratio 1.51 [95% CI 1.18-2.28], P = .02) and fewer VFD at 28 d (β -3.50 [95% CI -6.09 to 0.91], P = .008). Those with NIV exposure prior to intubation also had higher rates of development of pediatric ARDS (95% vs 78%, P = .001).

CONCLUSIONS

In this cohort of children post-HCT, NIV use prior to intubation was associated with worse outcomes. The benefits and risks of NIV in this patient population should be carefully evaluated prior to its use, and careful patient selection is crucial for its optimal utilization.

Early pulmonary complications related to cancer treatment in children

In this review, we summarize early pulmonary complications related to cancer therapy in children and highlight characteristic findings on imaging that should be familiar to a radiologist reviewing imaging from pediatric cancer patients.

Comparison of Pulmonary Toxicity after Total Body Irradiation- and Busulfan-Based Myeloablative Conditioning for Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients

Pulmonary toxicity after allogeneic hematopoietic stem cell transplantation (allo-HSCT) for childhood leukemia and myelodysplastic syndrome (MDS), along with the impact of different myeloablative conditioning regimens, remain incompletely described. Here we compared the acute and long-term incidence of pulmonary toxicity (PT) after total body irradiation (TBI)- and busulfan-based myeloablative conditioning. We conducted this retrospective cohort study of 311 consecutive pediatric patients with leukemia or MDS who underwent allo-HSCT at Dana-Farber Cancer Institute/Boston Children's Hospital between 2008 and 2018. PT was graded using Common Terminology Criteria for Adverse Events version 5.0. The primary objective was to compare the cumulative incidence of grade ≥3 and grade 5 PT after TBI-based and busulfan-based myeloablative conditioning using Gray's test. Secondary objectives were to determine factors associated with PT and overall survival (OS) using competing risk analysis and Cox regression analyses, respectively. There was no significant difference between the TBI-conditioned group (n = 227) and the busulfan-conditioned group (n = 84) in the incidence of grade ≥3 PT (29.2% versus 34.7% at 2 years; P = .26) or grade 5 pulmonary toxicity (6.2% versus 6.1% at 2 years; P = .47). Age (hazard ratio [HR], 1.70, 95% confidence interval [CI], 1.11 to 2.59; P = .01), grade ≥2 PT prior to allo-HSCT or preexisting pulmonary conditions (HR, 1.84, 95% CI, 1.24 to 2.72; P < .01), acute graft-versus-host disease (GVHD) (HR, 2.50; 95% CI, 1.51 to 4.14; P < .01), and chronic GVHD (HR, 2.61; 95% CI, 1.26 to 5.42; P = .01) were associated with grade ≥3 PT on multivariable analysis. Grade ≥3 PT was associated with worse OS (81.1% versus 61.5% at 2 years; P < .01). In pediatric allo-HSCT recipients, rates of PT were similar in recipients of TBI-based and recipients of busulfan-based myeloablative conditioning regimens. Age, the presence of PT or preexisting pulmonary conditions prior to transplantation, and the development of either acute or chronic GVHD were associated with grade ≥3 PT post-transplantation. Furthermore, the occurrence of grade 3-4 PT post-transplantation was associated with inferior OS.

Interstitial lung disease with anti-melanoma differentiation-associated gene 5 antibody after allogeneic hematopoietic stem cell transplantation

Anti-melanoma differentiation-associated gene 5 (MDA5) antibody is one of auto-immune antibodies which is associated with a rare subtype of dermatomyositis (DM), and MDA5-DM is well-characterized by rapid progressive interstitial lung disease (ILD) which in part resembles pulmonary complications after allogeneic hematopoietic cell transplantation (allo-HCT). However, previous studies about anti-MDA5 antibody after allo-HCT were extremely limited. Here, we present 4 cases of ILD with anti-MDA5 antibody after allo-HCT. All of the cases showed rapidly progressive clinical course and 3 of 4 cases died despite intensive immunosuppressive therapies which included prednisolone, cyclophosphamide and calcineurin inhibitor. Additionally, 3 of 4 cases had tested positive for anti-MDA5 antibody by using cryopreserved plasma which were collected about 2–3 months before the diagnosis of MDA5-DM-ILD. It suggests that an inflammatory condition due to MDA5-DM-ILD might have sub-clinically occurred before the development of respiratory failure. The current cases suggest that the clinical feature was relatively similar to classical MDA5-DM-ILD, although it is difficult to distinguish MDA5-DM-ILD from chronic GVHD and other pulmonary complications after allo-HCT. Since clinical courses of MDA5-DM-ILD is considerably aggressive, it is important to discriminate MDA5-DM-ILD from other complications after allo-HCT.

A Systematic Review on Pulmonary Complications Secondary to Hematopoietic Stem Cell Transplantation

The main purpose of this systematic review was to identify and synthesize evidence about pulmonary complications following stem cell transplantation to raise awareness among physicians since it is a lesser-known topic. Studies that included targeted pulmonary complications that occurred after stem cell transplantation; in humans; and were randomized controlled trials, cohort studies, and case studies between January 2011 and 2021. Fifteen intervention features were identified and analyzed in terms of their association with successful or unsuccessful interventions. Fifteen of 15 studies that met inclusion criteria had positive results. Features that appeared to have the most consistent positive effects included relevant information consisting of clinical presentations and management of complications. 

Hematopoietic stem cell transplantation is a therapeutic method that has been introduced for various hematological diseases. Its main objective is to restore the hematopoietic function that has been eradicated or affected. The stem cell transplantation requires a period of administration of chemotherapeutic agents that may lead to infectious and/or non-infectious pulmonary complications that require follow-up.

Noninfectious pulmonary complications include bronchiolitis obliterans, alveolar hemorrhage, fibroelastosis, pulmonary hypertension, and infections. Bronchiolitis obliterans syndrome is an obstructive lung disease that affects the small airways, reducing lung function, and it’s the most frequent late-onset complication. Furthermore, diffuse pulmonary hemorrhage is a fatal adverse effect and the most common noninfectious pulmonary complication of acute leukemia, observed within the first weeks after the procedure. Pulmonary hypertension has multiple etiologies, mainly related to the pulmonary veno-occlusive disease. It carries a poor prognosis, with a 55% mortality rate. The area of hematology is very wide and prone to new development of treatments and procedures that could be available for new emerging diseases and improving survival rates. 

Pulmonary microbiome and gene expression signatures differentiate lung function in pediatric hematopoietic cell transplant candidates

Impaired baseline lung function is associated with mortality after pediatric allogeneic hematopoietic cell transplantation (HCT), yet limited knowledge of the molecular pathways that characterize pretransplant lung function has hindered the development of lung-targeted interventions. In this study, we quantified the association between bronchoalveolar lavage (BAL) metatranscriptomes and paired pulmonary function tests performed a median of 1 to 2 weeks before allogeneic HCT in 104 children in The Netherlands. Abnormal pulmonary function was recorded in more than half the cohort, consisted most commonly of restriction and impaired diffusion, and was associated with both all-cause and lung injury-related mortality after HCT. Depletion of commensal supraglottic taxa, such as Haemophilus, and enrichment of nasal and skin taxa, such as Staphylococcus, in the BAL microbiome were associated with worse measures of lung capacity and gas diffusion. In addition, BAL gene expression signatures of alveolar epithelial activation, epithelial-mesenchymal transition, and down-regulated immunity were associated with impaired lung capacity and diffusion, suggesting a postinjury profibrotic response. Detection of microbial depletion and abnormal epithelial gene expression in BAL enhanced the prognostic utility of pre-HCT pulmonary function tests for the outcome of post-HCT mortality. These findings suggest a potentially actionable connection between microbiome depletion, alveolar injury, and pulmonary fibrosis in the pathogenesis of pre-HCT lung dysfunction.

A biomarker panel for risk of early respiratory failure following hematopoietic cell transplantation

This study identified and validated ST2, WFDC2, IL-6, and TNFR1 as risk biomarkers for RF and related mortality post-HCT.

Plasma biomarkers associated with respiratory failure (RF) following hematopoietic cell transplantation (HCT) have not been identified. Therefore, we aimed to validate early (7 and 14 days post-HCT) risk biomarkers for RF. Using tandem mass spectrometry, we compared plasma obtained at day 14 post-HCT from 15 patients with RF and 15 patients without RF. Six candidate proteins, from this discovery cohort or identified in the literature, were measured by enzyme-linked immunosorbent assay in day-7 and day-14 post-HCT samples from the training (n = 213) and validation (n = 119) cohorts. Cox proportional-hazard analyses with biomarkers dichotomized by Youden’s index, as well as landmark analyses to determine the association between biomarkers and RF, were performed. Of the 6 markers, Stimulation-2 (ST2), WAP 4-disulfide core domain protein 2 (WFDC2), interleukin-6 (IL-6), and tumor necrosis factor receptor 1 (TNFR1), measured at day 14 post-HCT, had the most significant association with an increased risk for RF in the training cohort (ST2: hazard ratio [HR], 4.5, P = .004; WFDC2: HR, 4.2, P = .010; IL-6: HR, 6.9, P < .001; and TFNR1: HR, 6.1, P < .001) and in the validation cohort (ST2: HR, 23.2, P = .013; WFDC2: HR, 18.2, P = .019; IL-6: HR, 12.2, P = .014; and TFNR1: HR, 16.1, P = .001) after adjusting for the conditioning regimen. Using cause-specific landmark analyses, including days 7 and 14, high plasma levels of ST2, WFDC2, IL-6, and TNFR1 were associated with an increased HR for RF in the training and validation cohorts. These biomarkers were also predictive of mortality from RF. ST2, WFDC2, IL-6 and TNFR1 levels measured early posttransplantation improve risk stratification for RF and its related mortality.

Noninfectious complications of hematopoietic cell transplantation

Noninfectious lung diseases contribute to nonrelapse mortality. They constitute a spectrum of diseases that can affect the parenchyma, airways, or vascular pulmonary components and specifically exclude cardiac and renal causes. The differential diagnoses of these entities differ as a function of time after hematopoietic cell transplantation. Specific diagnosis, prognosis, and optimal treatment remain challenging, although progress has been made in recent decades.

Successful ruxolitinib administration for a patient with steroid-refractory idiopathic pneumonia syndrome following hematopoietic stem cell transplantation: A case report and literature review

Idiopathic pneumonia syndrome (IPS) is an acute lung complication observed after the early posthematopoietic stem cell transplantation (HSCT) period. Ruxolitinib was effective for a patient with myelodysplastic syndrome who developed severe IPS after second HSCT. No severe adverse effects were observed. Ruxolitinib may be an alternative choice for HSCT-related IPS.

Hematopoietic Cell Transplantation-Comorbidity Index Score Is Correlated with Treatment-Related Mortality and Overall Survival following Second Allogeneic Hematopoietic Cell Transplantation in Children

Allogeneic hematopoietic cell transplantation (HCT) can lead to considerable complications and treatment-related mortality (TRM); therefore, a detailed assessment of risks is essential. The Hematopoietic Cell Transplantation-Comorbidity Index (HCT-CI) can predict both TRM and overall survival (OS). Although the HCT-CI has been validated as a useful tool for first HCT, its potential utility for second HCT has not yet been investigated. Here we aimed to evaluate the utility of the HCT-CI score in assessing the risk of TRM and OS in the setting of a second allogeneic HCT. This was a retrospective analysis of all pediatric patients (age <21 years) who underwent a second allogeneic HCT at UCSF Benioff Children's Hospital San Francisco between 2008 and 2019. According to their HCT-CI, patients were classified as "low risk" with an HCT-CI of 0 or "intermediate-high risk" with an HCT-CI ≥1. A total of 59 patients were included in the study. Our primary endpoint was TRM, observed at 100 days, 180 days, 1 year, and last follow-up following HCT, and our secondary endpoint was OS at 1 year and at 5 years or last follow-up. We also evaluated outcomes of patients admitted to the pediatric intensive care unit based on the HCT-CI score. Seventy-six percent of patients had an HCT-CI of 0. The most frequent comorbidities were pulmonary, seen in 7 patients (12%; 95% CI, 5% to 23%), including 5 (71%) with moderate and 2 (29%) with severe comorbidities. The OS and the cumulative incidence of TRM at 1 year for the entire cohort were 81% (95% CI, 69% to 90%) and 12% (95% CI, 5% to 22%), respectively. The cumulative incidence of TRM and OS at 1 year showed a significant correlation with HCT-CI score; TRM was 4% (95% CI, 1% to 13%) for an HCT-CI of 0 versus 36% (95% CI, 13% to 60%) for an HCT-CI ≥1 (P < .001), and OS was 89% (95% CI, 75% to 99%) for an HCT-CI of 0 versus 57% (95% CI, 28% to 78%) for an HCT-CI ≥1 (P = .003). After adjusting for covariates, HCT-CI continued to be associated with both TRM (P = .004) and OS (P = .003). In addition, comparing patients with malignancies and nonmalignant disorders, disease-free-survival at last follow-up was higher in the nonmalignant disorder group and also was influenced by the HCT-CI score in each group (P = .0035). There also was a significant difference in outcomes of patients admitted to the pediatric intensive care unit; 15 patients (68%) with an HCT-CI of 0 were alive at last follow-up, compared with only two (22%) with an HCT-CI ≥1 (P = .016). HCT-CI has an impact on TRM and OS and may serve as a predictor of outcomes of second allogeneic transplantation. Although this study was conducted in a relatively small sample, it is the first to investigate the utility of the HCT-CI score in predicting outcomes after a second allogeneic HCT in pediatric recipients. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Pulmonary Complications of Pediatric Hematopoietic Cell Transplantation. A National Institutes of Health Workshop Summary

Approximately 2,500 pediatric hematopoietic cell transplants (HCTs), most of which are allogeneic, are performed annually in the United States for life-threatening malignant and nonmalignant conditions. Although HCT is undertaken with curative intent, post-HCT complications limit successful outcomes, with pulmonary dysfunction representing the leading cause of nonrelapse mortality. To better understand, predict, prevent, and/or treat pulmonary complications after HCT, a multidisciplinary group of 33 experts met in a 2-day National Institutes of Health Workshop to identify knowledge gaps and research strategies most likely to improve outcomes. This summary of Workshop deliberations outlines the consensus focus areas for future research.

Pulmonary surveillance in pediatric hematopoietic stem cell transplant: A multinational multidisciplinary survey

Background

Hematopoietic Stem Cell Transplant (HSCT) is an established treatment for malignant and non‐malignant conditions and pulmonary disease is a leading cause of late term morbidity and mortality. Accurate and early detection of pulmonary complications is a critical step in improving long term outcomes. Existing guidelines for surveillance of pulmonary complications post‐HSCT contain conflicting recommendations.

Aim

To determine the breadth of current practice in monitoring for pulmonary complications of pediatric HSCT.

Methods

An institutional review board approved, online, anonymous multiple‐choice survey was distributed to HSCT and pulmonary physicians from the United States of America and Australasia using the REDcap platform. The survey was developed by members of the American Thoracic Society Working Group on Complications of Childhood Cancer, and was designed to assess patient management and service design.

Results

A total of 40 (34.8%) responses were received. The majority (62.5%) were pulmonologists, and 82.5% were from the United States of America. In all, 67.5% reported having a protocol for monitoring pulmonary complications and 50.0% reported adhering “well” or “very well” to protocols. Pulmonary function tests (PFTs) most commonly involved spirometry and diffusion capacity for carbon monoxide. The frequency of PFTs varied depending on time post‐HSCT and presence of complications. In all, 55.0% reported a set threshold for a clinically significant change in PFT.

Conclusions

These results illustrate current variation in surveillance for pulmonary complications of pediatric HSCT. The results of this survey will inform development of future guidelines for monitoring of pulmonary complications after pediatric HSCT.

Quantitative inspiratory-expiratory chest CT to evaluate pulmonary involvement in pediatric hematopoietic stem-cell transplantation patients

Pulmonary complications following allogeneic hematopoietic stem-cell transplantation (HSCT) are a significant source of morbidity and complications may arise from a myriad of infectious and noninfectious sources. These complications may occur soon or many months post-transplantation and can have a broad range of outcomes. Surveillance for pulmonary involvement in the pediatric HSCT population can be challenging due to poor compliance with clinical pulmonary function testing, primarily spirometry, and there may be a role for clinical imaging to provide an additional means of monitoring, particularly in the era of clinical low-dose computed tomography (CT) protocols. In this single-site, retrospective study, a review of our institution's radiological and HSCT databases was conducted to assess the utility of a quantitative CT algorithm to describe ventilation abnormalities on high-resolution chest CT scans of pediatric HSCT patients. Thirteen non-contrast enhanced chest CT examinations acquired both in inspiration and expiration, from 12 deceased HSCT patients (median age at HSCT 10.4 years, median days of CT 162) were selected for the analysis. Also, seven age-matched healthy controls (median age 15.5) with non-contrast-enhanced inspiration-expiration chest CT were selected for comparison. We report that, compared to healthy age-matched controls, HSCT patients had larger percentages of poorly ventilated (median, 13.5% vs. 2.3%, p < .001) and air trapped (median 12.3% vs. 0%, p < .001) regions of lung tissue, suggesting its utility as a potential screening tool. Furthermore, there was wide variation within individual HSCT patients, supporting the use of multivolume CT and quantitative analysis to describe and phenotype post-transplantation lung involvement.

The pulmonary metatranscriptome prior to pediatric HCT identifies post-HCT lung injury

Lung injury after pediatric allogeneic hematopoietic cell transplantation (HCT) is a common and disastrous complication that threatens long-term survival. To develop strategies to prevent lung injury, novel tools are needed to comprehensively assess lung health in HCT candidates. Therefore, this study analyzed biospecimens from 181 pediatric HCT candidates who underwent routine pre-HCT bronchoalveolar lavage (BAL) at the University Medical Center Utrecht between 2005 and 2016. BAL fluid underwent metatranscriptomic sequencing of microbial and human RNA, and unsupervised clustering and generalized linear models were used to associate microbiome gene expression data with the development of post-HCT lung injury. Microbe-gene correlations were validated using a geographically distinct cohort of 18 pediatric HCT candidates. The cumulative incidence of post-HCT lung injury varied significantly according to 4 pre-HCT pulmonary metatranscriptome clusters, with the highest incidence observed in children with pre-HCT viral enrichment and innate immune activation, as well as in children with profound microbial depletion and concomitant natural killer/T-cell activation (P < .001). In contrast, children with pre-HCT pulmonary metatranscriptomes containing diverse oropharyngeal taxa and lacking inflammation rarely developed post-HCT lung injury. In addition, activation of epithelial-epidermal differentiation, mucus production, and cellular adhesion were associated with fatal post-HCT lung injury. In a separate validation cohort, associations among pulmonary respiratory viral load, oropharyngeal taxa, and pulmonary gene expression were recapitulated; the association with post-HCT lung injury needs to be validated in an independent cohort. This analysis suggests that assessment of the pre-HCT BAL fluid may identify high-risk pediatric HCT candidates who may benefit from pathobiology-targeted interventions.

Diffuse Alveolar Hemorrhage After Pediatric Hematopoietic Stem Cell Transplantation

Pulmonary complications are common following hematopoietic cell transplantation (HCT) and contribute significantly to its morbidity and mortality. Diffuse alveolar hemorrhage is a devastating non-infectious complication that occurs in up to 5% of patients post-HCT. Historically, it carries a high mortality burden of 60–100%. The etiology remains ill-defined but is thought to be due to lung injury from conditioning regimens, total body irradiation, occult infections, and other comorbidities such as graft vs. host disease, thrombotic microangiopathy, and subsequent cytokine release and inflammation. Clinically, patients present with hypoxemia, dyspnea, and diffuse opacities consistent with an alveolar disease process on chest radiography. Diagnosis is most commonly confirmed with bronchoscopy findings of progressively bloodier bronchoalveolar lavage or the presence of hemosiderin-laden macrophages on microscopy. Treatment with glucocorticoids is common though dosing and duration of therapy remains variable. Other agents, such as aminocaproic acid, tranexamic acid, and activated recombinant factor VIIa have also been tried with mixed results. We present a review of diffuse alveolar hemorrhage with a focus on its pathogenesis and treatment options.

Effect of Smoking on Outcomes of Allogeneic Transplantation: A Single-Center Analysis

Pulmonary complications are fatal adverse events after allogeneic hematopoietic cell transplantation (allo-HCT). On the other hand, smoking is a well-known risk factor for various pulmonary diseases and also increases the incidence of pulmonary complications and overall mortality in allo-HCT recipients. In this study, we retrospectively assessed the impact of smoking intensity on survival outcomes. This study included consecutive allo-HCT recipients at our center between June 2007 and May 2019 whose smoking profiles were available (n = 408); they were divided into high (pack-years >10, n = 171) and low (pack-years ≤10, n = 231) pack-years groups. In univariate analyses, nonrelapse mortality (NRM) and overall survival (OS) were significantly inferior in the high pack-years group (1-year NRM 26.6% versus 13.9%, P < .001; 1-year OS 58.4% versus 70.1%, P = .0067). However, this association was not observed in multivariate analyses. In subgroup analyses according to sex, the survival outcomes in the high pack-years group were significantly inferior in males (NRM hazard ratio [HR], 2.24 [95% confidence interval (CI), 1.23 to 4.07], P = .0082; OS HR, 1.54 [95% CI, 1.04 to 2.28], P = .031), but not in females (NRM HR, 0.587 [95% CI, 0.241 to 1.43], P = .24; OS HR, 0.689 [95% CI, 0.400 to 1.19], P = .18). In summary, high pack-years were associated with inferior survival of allo-HCT recipients, especially in males.

Emergency imaging in paediatric oncology: a pictorial review

Despite the decline in mortality rates over the last 20 years, cancer remains one of the leading causes of death in children worldwide. Early recognition and treatment for acute oncological emergencies are vital in preventing mortality and poor outcomes, such as irreversible end-organ damage and a compromised quality of life.Imaging plays a pivotal and adjunctive role to clinical examination, and a high level of interpretative acumen by the radiologist can make the difference between life and death. In contrast to adults, the most accessible cross-sectional imaging tool in children typically involves ultrasound. The excellent soft tissue differentiation allows for careful delineation of malignant masses and along with colour Doppler imaging, thromboses and large haematomas can be easily identified. Neurological imaging, particularly in older children is an exception. Here, computed tomography (CT) is required for acute intracranial pathologies, with magnetic resonance imaging (MRI) providing more definitive results later.This review is divided into a 'body systems' format covering a range of pathologies including neurological complications (brainstem herniation, hydrocephalus, spinal cord compression), thoracic complications (airway obstruction, superior vena cava syndrome, cardiac tamponade), intra-abdominal complications (bowel obstruction and perforation, hydronephrosis, abdominal compartment syndrome) and haematological-related emergencies (thrombosis, infection, massive haemorrhage). Within each subsection, we highlight pertinent clinical and imaging considerations.The overall objective of this pictorial review is to illustrate how primary childhood malignancies may present with life-threatening complications, and emphasise the need for imminent patient management.