Management of Invasive Fungal Infections in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation: The Turin Experience

Risk factors for invasive fungal infections after haematopoietic stem cell transplantation: a systematic review and meta-analysis

BACKGROUND

Invasive fungal infections (IFIs) are common infectious complications after haematopoietic stem cell transplantation (HSCT), seriously threatening the survival of patients.

OBJECTIVES

This systematic review aimed to investigate risk factors associated with IFIs following HSCT.

METHODS

Two authors independently conducted the selection of studies and extraction of data. Risk factors for IFIs, invasive aspergillosis or invasive mould infections and invasive candida infection after HSCT were compiled separately by meta-analysis using RevMan 5.4 and R language 4.1.2.

DATA SOURCES

Pubmed, EMBASE, Web of Science, and the Cochrane Library until April 2023.

STUDY ELIGIBILITY CRITERIA

Case-control or cohort studies that assessed risk factors for IFIs among HSCT recipients were included.

PARTICIPANTS

Patients experiencing HSCT.

TEST/S

None.

REFERENCE STANDARD

The IFIs were defined according to the European Organisation for Research and Treatment of Cancer/Mycosis Study Group (EORTC/MSG) criteria, or a similar definition.

ASSESSMENT OF RISK OF BIAS

A modified version of the Newcastle-Ottawa Scale was used.

METHODS OF DATA SYNTHESIS

A random-effects model with the Mantel-Haenszel method was used to pool results from primary studies.

RESULTS

Out of 1637 studies screened, 51 studies involving 109 155 patients were included, with 45 studies providing adequate data for meta-analysis. Identified risk factors for IFIs included prolonged neutropenia, intensified therapy for graft-versus-host disease (GVHD), previous transplantation, previous proven or probable IFI, acute GVHD ≥ grade II, extensive or severe chronic GVHD, use of anti-thymocyte globulin during transplantation, haploidentical transplantation, high-dose glucocorticoids, Epstein-Barr virus infection, cytomegalovirus infection or reactivation, and lower albumin. Conversely, antifungal prophylaxis emerged as the sole preventive factor. For invasive aspergillosis or invasive mould infections, the top risk factors were extensive or severe chronic GVHD, respiratory viral infection, high-dose glucocorticoids, acute GVHD ≥ grade II, and human leukocyte antigen mismatch. Cord blood transplantation was the sole significant risk factor for invasive candidiasis. However, there was likely a high degree of interdependence among various risk factors.

DISCUSSION

This meta-analysis provides a thorough review of risk factors for IFIs infection after HSCT. The achieved insights can aid in stratifying patients who are at an elevated risk of IFIs and promoting antifungal preventive strategies.

Current status and new experimental diagnostic methods of invasive fungal infections after hematopoietic stem cell transplantation

Invasive fungal infections (IFIs) are common and life-threatening complications in post-hematopoietic stem cell transplantation (post-HSCT) recipients, Severe IFIs can lead to systemic infection and organ damage, which results in high mortality in HSCT recipients. With the development of the field of fungal infection diagnosis, more and more advanced non-culture diagnostic tools have been developed, such as glip biosensors, metagenomic next-generation sequencing, Magnetic Nanoparticles and Identified Using SERS via AgNPs+ , and artificial intelligence-assisted diagnosis. The advanced diagnostic approaches contribute to the success of HSCT and improve the overall survival of post-HSCT leukemia patients by supporting therapeutical decisions. This review provides an overview of the characteristics of two high-incidence IFIs in post-HSCT recipients and discusses some of the recently developed IFI detection technologies. Additionally, it explores the potential application of cationic conjugated polymer fluorescence resonance energy transfer (CCP-FRET) technology for IFI detection. The aim is to offer insights into selecting appropriate IFI detection methods and gaining an understanding of novel fungal diagnostic approaches in laboratory settings.

The epidemiology of invasive fungal infections in transplant recipients

Transplant patients, including solid-organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients, are exposed to various types of complications, particularly rejection. To prevent these outcomes, transplant recipients commonly receive long-term immunosuppressive regimens that in turn make them more susceptible to a wide array of infectious diseases, notably those caused by opportunistic pathogens. Among these, invasive fungal infections (IFIs) remain a major cause of mortality and morbidity in both SOT and HSCT recipients. Despite the continuing improvement in early diagnostics and treatments of IFIs, the management of these infections in transplant patients is still complicated. Here, we provide an overview concerning the most recent trends in the epidemiology of IFIs in SOT and HSCT recipients by describing the prominent yeast and mold species involved, the timing of post-transplant IFIs and the risk factors associated with their occurrence in these particularly weak populations. We also give special emphasis into basic research advances in the field that recently suggested a role of the global and long-term prophylactic regimen in orchestrating various biological disturbances in the organism and conditioning the emergence of the most adapted fungal strains to the particular physiological profiles of transplant patients.

Results of Levofloxacin Prophylaxis Timing in Autologous and Allogeneic Stem Cell Transplantation: A Retrospective Cohort Study

Background Despite preventive measures and varying antibiotic recommendations, bacterial infections continue to pose a significant threat to individuals undergoing hematopoietic stem cell transplantation (HSCT). Levofloxacin prophylaxis is commonly used, but the optimal timing for initiation is debated. This study aims to assess infection outcomes based on timing of levofloxacin prophylaxis (initiation at the first day of conditioning vs. after infusion of stem cells) in autologous and allogeneic HSCT patients. Methods We compared infectious episodes, responsible pathogens, and clinical outcomes based on the implementation of levofloxacin prophylaxis in patients receiving autologous or allogeneic HSCT procedures. This retrospective single-center study involved a review of the medical records of autologous and allogeneic HSCT patients treated at our adult stem cell transplantation unit between 2018 and 2020. The study included 23 patients who underwent autologous HSCT and 12 patients who underwent allogeneic HSCT. We compared the demographic data, febrile neutropenia, proven bacterial infections, and 30-day survival among the autologous and allogeneic transplant groups, including those who received oral levofloxacin 500 mg/day prophylaxis. Results Positive blood cultures (26.1% vs. 75%; p = 0.011), mean neutrophil engraftment (10.6±1.2 vs. 14.8±1.3; p<0.001), and mean platelet engraftment (11.2±1.1 vs. 15.4±3.2; p = 0.004) were all lower in autologous transplant patients versus their allogeneic counterparts. When each type of HSCT was evaluated within the same type, there were no observed differences in infection frequency, infection type, or 30-day mortality between the patient groups with different levofloxacin initiation times. Conclusion Healthcare professionals should choose the most appropriate timing for initiating levofloxacin prophylaxis based on individual patient factors and clinical circumstances while considering the cost-effectiveness implications. Further research with a larger sample size and prospective design is needed to support our findings.

High-Risk Neutropenic Fever and Invasive Fungal Diseases in Patients with Hematological Malignancies

Invasive fungal diseases (IFDs) still represent a relevant cause of mortality in patients affected by hematological malignancies, especially acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) undergoing remission induction chemotherapy, and in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Mold-active antifungal prophylaxis (MAP) has been established as a standard of care. However, breakthrough IFDs (b-IFDs) have emerged as a significant issue, particularly invasive aspergillosis and non-Aspergillus invasive mold diseases. Here, we perform a narrative review, discussing the major advances of the last decade on prophylaxis, the diagnosis of and the treatment of IFDs in patients with high-risk neutropenic fever undergoing remission induction chemotherapy for AML/MDS and allo-HSCT. Then, we present our single-center retrospective experience on b-IFDs in 184 AML/MDS patients undergoing high-dose chemotherapy while receiving posaconazole (n = 153 induction treatments, n = 126 consolidation treatments, n = 60 salvage treatments). Six cases of probable/proven b-IFDs were recorded in six patients, with an overall incidence rate of 1.7% (6/339), which is in line with the literature focused on MAP with azoles. The incidence rates (IRs) of b-IFDs (95% confidence interval (95% CI), per 100 person years follow-up (PYFU)) were 5.04 (0.47, 14.45) in induction (n = 2), 3.25 (0.0013, 12.76) in consolidation (n = 1) and 18.38 (3.46, 45.06) in salvage chemotherapy (n = 3). Finally, we highlight the current challenges in the field of b-IFDs; these include the improvement of diagnoses, the expanding treatment landscape of AML with molecular targeted drugs (and related drug-drug interactions with azoles), evolving transplantation techniques (and their related impacts on IFDs' risk stratification), and new antifungals and their features (rezafungin and olorofim).

Challenges in management of invasive fungal infections in stem cell transplant

Invasive fungal infections cause significant morbidity and mortality in hematopoietic stem cell transplant recipients. In order to minimize these infections, prophylaxis has become routine, although the agents used have changed over time. This presents new challenges as we consider an approach to breakthrough infections and recognize the epidemiologic shift toward isolates with higher rates of drug resistance. This review outlines the management of the most common pathogens (Candida, Aspergillus, Mucorales) as well as rarer pathogens that have higher rates of resistance (Trichosporon, Fusarium, Scedosporium, and Lomentospora). We discuss potential approaches to proven or possible breakthrough infections with yeast and pulmonary mold disease. Finally, we outline the role for combination therapy and newer antifungals, acknowledging current knowledge gaps and areas for future exploration.

Diagnostic efficiency of metagenomic next-generation sequencing for suspected infection in allogeneic hematopoietic stem cell transplantation recipients

Introduction

Immunosuppression predisposes allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients to infection. Prompt and accurate identification of pathogens is crucial to optimize treatment strategies. This multi-center retrospective study aimed to assess the ability of metagenomic next-generation sequencing (mNGS) to detect causative pathogens in febrile allo-HSCT recipients and examined its concordance with conventional microbiological tests (CMT).

Methods

We performed mNGS and CMT on samples obtained from 153 patients with suspected infection during allo-HSCT. Patients were grouped based on their neutropenic status at the time of sampling.

Results

The mNGS test was more sensitive than CMT (81.1% vs. 53.6%, P<0.001) for diagnosing clinically suspected infection, especially in the non-neutropenia cohort. mNGS could detect fungi and viruses better than bacteria, with a higher sensitivity than CMT. Immune events were diagnosed in 57.4% (35/61) of the febrile events with negative mNGS results, and 33.5% (48/143) with negative CMT results (P=0.002). The treatment success rate of the targeted anti-infection strategy was significantly higher when based on mNGS than on empirical antibiotics (85% vs. 56.5%, P=0.004).

Conclusion

The mNGS test is superior to CMT for identifying clinically relevant pathogens, and provides valuable information for anti-infection strategies in allo-HSCT recipients. Additionally, attention should be paid to immune events in patients with negative mNGS results.

Bacterial Bloodstream Infections after Allogeneic Hematopoietic Stem Cell Transplantation: Etiology, Risk Factors and Outcome in a Single-Center Study

Background—Allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients are subject to major risks for bacterial bloodstream infections (BSIs), including emergent multidrug-resistant (MDR) organisms, which still represent the main cause of morbidity and mortality in transplanted patients. Methods: We performed an observational, retrospective, single-center study on patients undergoing allo-HSCT between 2004 and 2020 at the Stem Cell Transplant Unit in Turin to assess the incidence, etiology, and outcomes of BSIs and to explore any risk factors for bacteriaemia. Results: We observed a total of 178 bacterial BSIs in our cohort of 563 patients, resulting in a cumulative incidence of 19.4%, 23.8%, and 28.7% at 30, 100, and 365 days, respectively. Among isolated bacteria, 50.6% were Gram positive (GPB), 41.6% were Gram negative (GNB), and 7.9% were polymicrobial infections. Moreover, BSI occurrence significantly influenced 1-year overall survival. High and very high Disease Risk Index (DRI), an haploidentical donor, and antibacterial prophylaxis were found as results as independent risk factors for bacterial BSI occurrence in multivariate analysis. Conclusions: In our experience, GNB have overwhelmed GPB, and fluoroquinolone prophylaxis has contributed to the emergence of MDR pathogens. Local resistance patterns and patients’ characteristics should therefore be considered for better management of bacteremia in patients receiving an allogeneic HSCT.

External evaluation of published population pharmacokinetic models of posaconazole

Population pharmacokinetic (PopPK) models of posaconazole have been established to promote the precision dosing. However, the performance of these models extrapolated to other centers has not been evaluated. This study aimed to conduct an external evaluation of published posaconazole PopPK models to evaluate their predictive performance. Posaconazole PopPK models screened from the PubMed and MEDLINE databases were evaluated using an external dataset of 213 trough concentration samples collected from 97 patients. Their predictive performance was evaluated by prediction-based diagnosis (prediction error), simulation-based diagnosis (visual predictive check), and Bayesian forecasting. In addition, external cohorts with and without proton pump inhibitor were used to evaluate the models respectively. Ten models suitable for the external dataset were finally included into the study. In prediction-based diagnostics, none of the models met pre-determined criteria for predictive indexes. Only M4, M6, and M10 demonstrated favorable simulations in visual predictive check. The prediction performance of M5, M7, M8, and M9 evaluated using the cohort without proton pump inhibitor showed a significant improvement compared to that evaluated using the whole cohort. Consistent with our expectations, Bayesian forecasting significantly improved the predictive per-formance of the models with two or three prior observations. In general, the applicability of these published posaconazole PopPK models extrapolated to our center was unsatisfactory. Prospective studies combined with therapeutic drug monitoring are needed to establish a PopPK model for posaconazole in the Chinese population to promote individualized dosing.