Prevention of veno-occlusive disease/sinusoidal obstruction syndrome: a never-ending story and no easy answer

Younger children with nonmalignant disease have increased incidence of mixed myeloid chimerism after allogeneic hematopoietic cell transplantation with busulfan-based conditioning

Successful allogeneic hematopoietic cell transplantation (HCT) for genetic nonmalignant diseases (NMD) is dependent upon elimination of host hematopoietic stem cells (HSCs) and replacement with donor HSCs in stable numbers sufficient to correct the underlying disease. Donor myeloid chimerism (DMC) in peripheral blood (PB) is a surrogate marker for bone marrow HSC engraftment due to the rapid turnover of PB myeloid cells. Busulfan is commonly used during conditioning for patients with NMD, though its optimal exposure to avoid inadequate DMC is not fully known. Younger patients with NMD have more mixed chimerism compared to older patients when receiving melphalan-based conditioning, possibly due to increased marrow reserve; we hypothesized that a similar phenomenon would occur with busulfan-based conditioning. We performed a retrospective analysis of 105 consecutive patients with NMDs (median age of 3.9 years) undergoing first allogeneic HCT with myeloablative (cAUC ≥55 mg*hr/L) busulfan-based conditioning from 2007 to 2023 and evaluated risk factors for the development of mixed (<95%) and minimal (≤20%) DMC. Receiver operating curve analysis demonstrated that age <2.9 years was the cut-off associated with mixed DMC. The cohort was therefore divided into two age groups: <3 years (43.8% of patients) and ≥3 years; there was no difference in busulfan exposure between the groups. The 3-year cumulative incidence of developing mixed DMC was 20.3% (95% CI, 12.1% to 28.5%). Age was associated with mixed DMC by 3 years post-HCT: 45.2% (95% CI, 29.7% to 60.7%) in those <3 years versus 1.9% (95% CI, 0.1% to 5.4%) in those ≥3 years (P < .001). Busulfan exposure was also associated with mixed DMC: 24.8% (95% CI, 14.8% to 34.8%) in those with cAUC 55 to 74.9 mg*hr/L versus 5% (95% CI, 0.1% to 8.3%) in those with cAUC ≥75 mg*hr/L (P = .03). In patients ≥3 years of age, there was no impact of busulfan exposure on development of mixed DMC. The 3-year cumulative incidence of developing minimal DMC was 5.5% (95% CI, 0.8% to 10.2%). Only young age was significantly associated with minimal DMC by 3 years post-HCT: 12.8% (95% CI, 2.2% to 23.4%) in those <3 years versus 0% (95% CI, 0% to 6.1%) in those ≥3 years (P = .008). There was no impact of age or busulfan exposure on immunologic graft rejection, acute or chronic graft-versus-host-disease, or transplant-related mortality. There was no difference in sinusoidal obstruction syndrome (SOS) incidence based on busulfan exposure: 13.7% (95% CI, 6.3% to 21.1%) for a cAUC of 55 to 74.9 mg*hr/L compared to 20.8% (95% CI, 4.5% to 37.1%) for a cAUC of ≥75 mg*hr/L (P = .33). However, the incidence of SOS was impacted by patient age: 32.9% (95% CI, 19.2% to 46.6%) in patients <3 years compared to 1.7% (95% CI, 0.1% to 5%) in patients ≥3 years (P < .001). Age <3 years at time of HCT is the major risk factor for mixed and minimal DMC in patients with NMD who receive busulfan-based conditioning. Patients ≥3 years of age may not require busulfan exposures above 55 to 60 mg*hr/L to develop full DMC. Conversely, to avoid development of mixed DMC, patients <3 years may benefit from either HCT delay (when feasible) or higher (≥75 mg*hr/L) busulfan exposure, albeit carrying a high-risk for SOS development.

Pharmacokinetics of post-transplant cyclophosphamide and its associations with clinical outcomes in pediatric haploidentical hematopoietic stem cell transplantation

BACKGROUND

Post-transplantation cyclophosphamide (PTCy) has paved the way for the increased use of alternative donors, including haploidentical familial donors, with acceptable engraftment and graft-versus-host disease (GVHD) rates. However, pharmacokinetic studies of PTCy in the pediatric population following myeloablative conditioning regimens are scarce.

METHODS

We conducted a prospective and comprehensive pharmacokinetic analysis of pre- and post-transplantation cyclophosphamide levels in pediatric patients undergoing haploidentical hematopoietic stem cell transplantation (HSCT) using a myeloablative busulfan-based conditioning regimen. A total of 14 samples were collected from each patient. Plasma concentrations of cyclophosphamide and carboxycyclophosphamide were analyzed, and clinical outcomes were recorded. The simulated pharmacokinetic profiles of cyclophosphamide and its metabolites were compared among different age groups using real-world data.

RESULTS

A total of 15 pediatric patients (median age at HSCT 9.6 years, range 1.6-16.8) were enrolled. Thirteen patients had malignant disease. All patients achieved successful neutrophil engraftment, and the cumulative incidences of grade 2-4 acute GVHD and moderate-to-severe chronic GVHD were 13.3% and 14.7%, respectively. The patterns of cyclophosphamide pharmacokinetic parameters were similar between the pre- and post-HSCT doses. The metabolic ratio increased with subsequent doses of PTCy. Patients with severe veno-occlusive disease showed a higher cumulative area under the curve (AUC) of carboxycyclophosphamide (62.6 vs. 40.2 mg x h/L, P = 0.025), while patients with > grade 3 hemorrhagic cystitis had a higher cumulative AUC of cyclophosphamide (1256.2 vs. 778.2 mg x h/L, P = 0.009). In contrast, there were no notable differences in the pharmacokinetic parameters of cyclophosphamide and carboxycyclophosphamide between the groups with and without acute and chronic GVHD. The AUC of cyclophosphamide and its metabolite were similar in children weighing ≥ 30 kg and the virtual adult population.

CONCLUSIONS

Our study provides insights into the pharmacokinetic profile of cyclophosphamide and its metabolite, carboxycyclophosphamide, in pediatric patients undergoing haploidentical HSCT with PTCy. The intricate interplay between pharmacokinetic parameters and post-HSCT complications suggests the need for tailored adjustments in PTCy dosage, particularly in pediatric patients subjected to myeloablative conditioning regimens.

The benefits of prophylactic defibrotide: Are the tides turning?

BACKGROUND

Veno-occlusive disease (VOD) is a life-threatening endotheliopathy that can occur after stem cell transplant (SCT). Numerous risk factors contribute to the development of VOD during SCT, and the role of prophylactic defibrotide (DF) in mitigating these risks remains unclear.

OBJECTIVE

We compare not only the incidence of VOD development, but also the severity of VOD and survival outcomes between patients who did and did not develop VOD and did or did not receive prophylactic DF.

STUDY DESIGN

In this single-center retrospective study of 58 pediatric SCT patients from 2008 to 2022, we compare the demographics, risk profiles, and outcomes within three cohorts: Group 1: prophylactic DF and no VOD (n = 5), Group 2: prophylactic DF and development of VOD (n = 6), and Group 3: treatment DF for patients who developed VOD (n = 47).

RESULTS

Patients with VOD who did not receive prophylactic DF had higher severity classification of disease at onset (very severe 80.9% vs. 66.7%, p = .592) and at maximum severity (very severe 89.4% vs. 83.3%, p = .532), as opposed to mild, moderate, or severe categorization compared to those who did not receive prophylactic DF. Patients who developed VOD and did not receive prophylactic DF had a lower 1-year survival probability compared to those who received prophylactic DF and still developed VOD (51.1% vs. 75% alive at 1 year, excluding the two subjects without adequate follow-up time, p = .266).

CONCLUSION

Although, not statistically significant in our small retrospective study, there is potential overall survival and decreased VOD severity benefits of prophylactic DF.

ANZTCT practice statement: sinusoidal obstruction syndrome/veno-occlusive disease diagnosis and management

Sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD) is a life-threatening complication which can develop after haemopoietic stem cell transplantation (HSCT) and some antibody-drug conjugates. Several SOS/VOD diagnostic and management guidelines exist, with the most recent and refined being the European Society for Blood and Marrow Transplantation adult and paediatric guidelines. Timely diagnosis and effective management (including the availability of therapeutic options) significantly contribute to improved patient outcomes. In Australia and New Zealand, there is variability in clinical practice and access to SOS/VOD therapies. This review aims to summarise the current evidence for SOS/VOD diagnosis, prevention and treatment and to provide recommendations for SOS/VOD in the context of contemporary Australasian HSCT clinical practice.

Diagnosing and Grading of Sinusoidal Obstructive Syndrome after Hematopoietic Stem Cell Transplant of Children, Adolescent and Young Adults treated in a Pediatric Institution with Pediatric Protocols

Sinusoidal obstructive syndrome (SOS), or veno-occlusive disease, of the liver has been recognized as a complex, life-threatening complication in the posthematopoietic stem cell transplant (HSCT) setting. The diagnostic criteria for SOS have evolved over the last several decades with a greater understanding of the underlying pathophysiology, with 2 recent diagnostic criteria introduced in 2018 (European Society of Bone Marrow Transplant [EBMT] criteria) and 2020 (Cairo criteria). We sought out to evaluate the performance characteristics in diagnosing and grading SOS in pediatric patients of the 4 different diagnostic criteria (Baltimore, Modified Seattle, EBMT, and Cairo) and severity grading systems (defined by the EBMT and Cairo criteria). Retrospective chart review of children, adolescent, and young adults who underwent conditioned autologous and allogeneic HSCT between 2017 and 2021 at a single pediatric institution. A total of 250 consecutive patients underwent at least 1 HSCT at UCSF Benioff Children's Hospital San Francisco for a total of 307 HSCT. The day 100 cumulative incidence of SOS was 12.1%, 21.1%, 28.4%, and 28.4% per the Baltimore, Modified Seattle, EBMT, and Cairo criteria, respectively (P < .001). We found that patients diagnosed with grade ≥4 SOS per the Cairo criteria were more likely to be admitted to the Pediatric Intensive Care Unit (92% versus 58%, P = .035) and intubated (85% versus 32%, P = .002) than those diagnosed with grade ≥4 per EBMT criteria. Age <3 years-old (HR 1.76, 95% [1.04 to 2.98], P = .036), an abnormal body mass index (HR 1.69, 95% [1.06 to 2.68], P = .027), and high-risk patients per our institutional guidelines (HR 1.68, 95% [1.02 to 2.76], P = .041) were significantly associated with SOS per the Cairo criteria. We demonstrate that age <3 years, abnormal body mass index, and other high-risk criteria associate strongly with subsequent SOS development. Patients with moderate to severe SOS based on Cairo severity grading system may correlate better with clinical course based on ICU admissions and intubations when compared to the EBMT severity grading system.

Retrospective analysis of veno-occlusive disease/sinusoidal obstruction syndrome in paediatric patients undergoing hematopoietic cell transplantation -a multicentre study

Background

Sinusoidal obstruction syndrome is a potentially fatal complication following hematopoietic cell transplantation, high-intensity chemotherapies and increasingly seen with calicheamicin based leukemia therapies. Paediatric specific European Society for Blood and Marrow Transplantation (pEBMT) diagnostic criteria have demonstrated benefit in single center studies compared to historic criteria. Yet, the extent to which they have been universally implemented remains unclear.

Methods

We conducted a retrospective multi-centre study to examine the potential impact of the Baltimore, modified Seattle and pEBMT criteria on the incidence, severity, and outcomes of sinusoidal obstruction syndrome among paediatric hematopoietic cell transplantation patients.

Findings

The incidence of sinusoidal obstruction syndrome in this cohort (n = 488) was higher by pEBMT (21.5%) vs historic modified Seattle (15.6%) and Baltimore (7.0%) criteria (p < 0.001). Application of pEBMT criteria identified 44 patients who were not previously diagnosed with sinusoidal obstruction syndrome. Overall, 70.5% of all patients diagnosed with sinusoidal obstruction syndrome ultimately developed very severe disease and almost half of diagnosed patients required critical care support. Overall survival was significantly lower in patients who were diagnosed with sinusoidal obstruction syndrome vs those who were not.

Interpretation

Taken together, pEBMT criteria may be a sensitive method for prompter diagnosis of patients who subsequently develop severe/very severe sinusoidal obstruction syndrome. To our knowledge, this is the first multi-centre study in the United States (US) to demonstrate that pEBMT guidelines are associated with earlier detection of sinusoidal obstruction syndrome. Since early initiation of definitive treatment for sinusoidal obstruction syndrome has been associated with improved survival in paediatric patients and implementation of pEBMT criteria appears feasible in the US, universal adoption should facilitate prompter diagnosis and lead to improved outcomes of children with sinusoidal obstruction syndrome.

Funding

None.