Risk factors and outcomes of diffuse alveolar haemorrhage after allogeneic haematopoietic stem cell transplantation

Pulmonary complications post allogeneic haematopoietic stem cell transplant in children

Objectives

Haematopoietic stem cell transplant (HCT) is a cellular therapy that, whilst curative for a child's underlying disease, carries significant risk of mortality, including because of pulmonary complications. The aims of this study were to describe the burden of pulmonary complications post-HCT in a cohort of Australian children and identify risk factors for the development of these complications.

Methods

Patients were identified from the HCT databases at two paediatric transplant centres in Australia. Medical records were reviewed, and demographics, HCT characteristics and pulmonary complications documented. Relative risk ratio was used to identify risk factors for developing pulmonary complications prior to first transplant episode, and survival analysis performed to determine hazard ratio.

Results

In total, 243 children underwent transplant during the study period, and pulmonary complications occurred in 48% (117/243) of children. Infectious complications were more common (55%) than non-infective complications (18%) and 26% of patients developed both. Risk factors for the development of pulmonary complications included the following: diagnoses of MPAL (RR 2.16, P = 0.02), matched unrelated donor (RR1.34, P = 0.03), peripheral blood (RR 1.36, P = 0.028) or cord blood (RR 1.73, P = 0.012) as the stem cell source and pre-existing lung disease (RR1.72, P < 0.0001). Children with a post-HCT lung complication had a significantly increased risk of mortality compared with those who did not (HR 3.9, P < 0.0001).

Conclusion

This study demonstrates pulmonary complications continue to occur frequently in children post-HCT and contribute significantly to mortality. Highlighting the need for improved strategies to identify patients at risk pre-transplant and enhanced treatments for those who develop lung disease.

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.

Clinical risk factors and prognostic model for patients with bronchiolitis obliterans syndrome after hematopoietic stem cell transplantation

Bronchiolitis obliterans syndrome (BOS) is a common and potentially devastating noninfectious pulmonary complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Currently, predictive tools for BOS are not available. We aimed to identify the clinical risk factors and establish a prognostic model for BOS in patients who undergo allo-HSCT. We retrospectively identified a cohort comprising 195 BOS patients from 6100 consecutive patients who were allografted between 2008 and 2022. The entire cohort was divided into a derivation cohort and a validation cohort based on the time of transplantation. Via multivariable Cox regression methods, declining forced expiratory volume at 1 s (FEV1) to <40%, pneumonia, cGVHD except lung, and respiratory failure were found to be independent risk factors for the 3-year mortality of BOS. A risk score called FACT was constructed based on the regression coefficients. The FACT model had an AUC of 0.863 (95% CI: 0.797-0.928) in internal validation and 0.749 (95% CI: 0.621-0.876) in external validation. The calibration curves showed good agreement between the FACT-predicted probabilities and actual observations. The FACT risk score will help to identify patients at high risk and facilitate future research on developing novel, effective interventions to personalize treatment.

Diffuse Alveolar Hemorrhage in Hematopoietic Cell Transplantation

Diffuse alveolar hemorrhage (DAH) is a morbid syndrome that occurs after autologous and allogeneic hematopoietic cell transplantation in children and adults. DAH manifests most often in the first few weeks following transplantation. It presents with pneumonia-like symptoms and acute respiratory failure, often requiring high levels of oxygen supplementation or mechanical ventilatory support. Hemoptysis is variably present. Chest radiographs typically feature widespread alveolar filling, sometimes with peripheral sparing and pleural effusions. The diagnosis is suspected when serial bronchoalveolar lavages return increasingly bloody fluid. DAH is differentiated from infectious causes of alveolar hemorrhage when extensive microbiological testing reveals no pulmonary pathogens. The cause is poorly understood, though preclinical and clinical studies implicate pretransplant conditioning regimens, particularly those using high doses of total-body-irradiation, acute graft-versus-host disease (GVHD), medications used to prevent GVHD, and other factors. Treatment consists of supportive care, systemic corticosteroids, platelet transfusions, and sometimes includes antifibrinolytic drugs and topical procoagulant factors. Therapeutic blockade of tumor necrosis factor-α showed promise in observational studies, but its benefit for DAH remains uncertain after small clinical trials. Even with these treatments, mortality from progression and relapse is high. Future investigational therapies could target the vascular endothelial cell biology theorized to contribute to alveolar bleeding and pathways that contribute to susceptibility, inflammation, cellular resilience, and tissue repair. This review will help clinicians navigate through the limited evidence to diagnose and treat DAH, counsel patients and families, and plan for future research.

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.

Clinical characteristics of late-onset interstitial pneumonia after allogeneic hematopoietic stem cell transplantation

Non-infectious pulmonary complications after allogeneic hematopoietic stem cell transplantation (HSCT) remain fatal. In particular, information regarding late-onset interstitial lung disease predominantly including organizing pneumonia and interstitial pneumonia (IP) is limited. A retrospective nationwide survey was conducted using data collected from the Japanese transplant outcome registry database from 2005 to 2010. This study focused on patients (n = 73) with IP diagnosed after day 90 post-HSCT. A total of 69 (94.5%) patients were treated with systemic steroids, and 34 (46.6%) experienced improvement. The presence of chronic graft-versus-host disease at the onset of IP was significantly associated with non-improvement of symptoms (odds ratio [OR] 0.35). At the time of last follow-up (median, 1471 days), 26 patients were alive. Of the 47 deaths, 32 (68%) were due to IP. The 3-year overall survival (OS) and non-relapse mortality (NRM) rates were 38.8% and 51.8%, respectively. In the multivariate analysis, the predictive factors for OS were comorbidities at IP onset (hazard ratio [HR]: 2.19) and performance status (PS) score of 2-4 (HR 2.77). Furthermore, cytomegalovirus reactivation requiring early intervention (HR 2.04), PS score of 2-4 (HR 2.63), and comorbidities at IP onset (HR 2.90) were also significantly associated with increased risk of NRM.

Efficacy and safety of avatrombopag for thrombocytopenia following allogeneic hematopoietic stem cell transplantation: A real-world data evaluation on 14 cases

OBJECTIVES

Thrombocytopenia following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a common and serious complication that leads to an increased risk of bleeding and poor prognosis. Traditional strategies consist of platelet transfusion, glucocorticoid therapy, intravenous human immunoglobulin, recombinant human thrombopoietin injection, and CD34+-selected hematopoietic stem cell transplantation, but the effects of these treatments are not satisfactory and the treatment continues to be challenged. This study aims to determine the treating efficacy of avatrombopag, a novel thrombopoietin receptor agonist, on thrombocytopenia after allo-HSCT, and to increase the evidence-based medical evidence for the clinical use of this drug.

METHODS

Fourteen patients with thrombocytopenia after allo-HSCT underwent avatrom-bopag treatment from September 2020 to September 2021 were retrospectively studied. Of these patients, 8 patients had delayed platelet engraftment (DPE) and 6 cases had secondary failure of platelet recovery (SFPR). The efficacy and safety of the treatment and the survival of the patients were assessed.

RESULTS

The median treatment time of avatrombopag was 34 days, and no patients stopped treatment due to adverse reactions or drug intolerance. Compared with the treatment before, the levels of platelet count, megakaryocytes, and hemoglobin in patients were significantly increased (P=0.000 1, P=0.001 0, and P=0.001 7, respectively). The optimal platelet count of 13 patients reached the complete response standard after drug withdrawal. The median follow-up time of 14 patients was 371 days, and the 2-year overall survival rate was 78.6%.

CONCLUSIONS

Avatrombopag is effective on increasing platelet counts in patients with thrombocytopenia after allo-HSCT, with a good safety profile. It is a suitable therapeutic option for thrombocytopenia after allo-HSCT.

A pilot trial of prophylactic defibrotide to prevent serious thrombotic microangiopathy in high-risk pediatric patients

BACKGROUND

Transplant-associated thrombotic microangiopathy (TA-TMA) is an endothelial injury complication of hematopoietic stem cell transplant (HSCT) leading to end-organ damage and high morbidity and mortality. Defibrotide is an anti-inflammatory and antithrombotic agent that may protect the endothelium during conditioning.

PROCEDURE

We hypothesized that prophylactic use of defibrotide during HSCT conditioning and acute recovery could prevent TA-TMA. A pilot single-arm phase II trial (NCT#03384693) evaluated the safety and feasibility of administering prophylactic defibrotide to high-risk pediatric patients during HSCT and assessed if prophylactic defibrotide prevented TA-TMA compared to historic controls. Patients received defibrotide 6.25 mg/kg IV q6h the day prior to the start of conditioning through day +21. Patients were prospectively monitored for TA-TMA from admission through week 24 post transplant. Potential biomarkers of endothelial injury (suppression of tumorigenicity 2 [ST2], angiopoietin-2 [ANG-2], plasminogen activator inhibitor-1 [PAI-1], and free hemoglobin) were analyzed.

RESULTS

Twenty-five patients were enrolled, 14 undergoing tandem autologous HSCT for neuroblastoma and 11 undergoing allogeneic HSCT. Defibrotide was discontinued early due to possibly related clinically significant bleeding in 12% (3/25) of patients; no other severe adverse events occurred due to the study intervention. The other 22 patients missed a median of 0.7% of doses (0%-5.2%). One patient developed nonsevere TA-TMA 12 days post HSCT. This observed TA-TMA incidence of 4% was below the historic rate of 18%-40% in a similar population of allogeneic and autologous patients.

CONCLUSIONS

Our study provides evidence that defibrotide prophylaxis is feasible in pediatric patients undergoing HSCT at high risk for TA-TMA and preliminary data indicating that defibrotide may reduce the risk of TA-TMA.