Radiology-based diagnosis of fungal pulmonary infections in high-risk hematology patients: are we making progress?

American Society of Transplantation and Cellular Therapy Series: #8-Management and Prevention of Non-Aspergillus Molds in Hematopoietic Cell Transplantation Recipients

The Practice Guidelines Committee of the American Society of Transplantation and Cellular Therapy partnered with its Transplant Infectious Disease Special Interest Group to create a guideline focusing on non-Aspergillus invasive molds, which are uncommon yet lethal invasive fungal diseases in the peri-hematopoietic cell transplant (HCT) period. We used a compendium-style approach by dissecting this broad, heterogeneous, and highly complex topic into a series of standalone frequently asked questions (FAQs) and tables. Adult and pediatric infectious diseases and HCT content experts developed, then answered FAQs, and finalized topics with harmonized recommendations. All the evidence for non-Aspergillus invasive mold infection is non-RCT and mostly level III, therefore there are no recommendation grades, and instead key references are provided. Through this format, this "8th" topic in the series focuses on the relevant risk factors, diagnostic considerations, prophylaxis, and treatment approaches relevant to rare mold infections in the pre- and post-transplant periods.

Refractory versus resistant invasive aspergillosis

Despite notable progress, the management of invasive aspergillosis (IA) remains challenging and treatment failures are common. The final patient outcome is subject to multiple factors including the host (the severity of the underlying conditions), the fungus (the virulence and susceptibility pattern of the Aspergillus species involved), and the therapy (the timing related to severity of infection and choice of therapy-dose, efficacy, cidal versus static, toxicity and interaction). Consequently, assessment of failure is complex yet crucial in order to ensure appropriate management. Refractoriness in absence of drug resistance may reflect severity of the underlying disease/infection at the time of initiation of therapy prolonging time to response. It may also reflect a suboptimal antifungal drug exposure due to poor compliance, inappropriate dosing or increased drug metabolism, or it may reflect 'pseudo' failure due to worsening of imaging due to recovery of neutrophils. Refractoriness may also be related to inherent drug resistance in various Aspergillus species or acquired resistance in a normally susceptible species. The latter scenario is mostly encountered in A. fumigatus, where azole resistance is increasing and includes azole-naive patients due to resistance related to azole fungicide use in agriculture and horticulture. Although diagnostics and resistance detection have been greatly improved, the time to resistance reporting is often still suboptimal, which calls for close assessment and potentially management changes even before the susceptibility is known. In this article we address the various definitions and approaches to assessment and management of clinical refractoriness/failure in the setting of proven and probable IA.

Concordance of Chest Radiography and Chest Computed Tomography Findings in Patients with Hematologic Malignancy and Invasive Mucormycosis: What Are the Prognostic Implications?

Invasive pulmonary mucormycosis (IPM) is a deadly opportunistic mold infection in patients with hematological malignancies (HM). Radiologic imaging is essential for its timely diagnosis. Here, we compared IPM lesions visualized by chest computed tomography (CCT) and chest X-ray (CXR) and determined the prognostic significance of discordant imaging. Therefore, we reviewed 44 consecutive HM patients with probable/proven IPM at MD Anderson Cancer Center in 2000-2020 who had concurrent CCT and CXR studies performed. All 44 patients had abnormal CCTs and 39 (89%) had anormal CXR findings at IPM diagnosis. However, only 26 patients (59%) showed CCT-matching IPM-suspicious lesions on CXR. Acute Physiology and Chronic Health Evaluation II score > 18 at IPM diagnosis and breakthrough infection to Mucorales-active antifungals were the only independent risk factors for 42-day and/or 84-day mortality. Absence of neutropenia at IPM diagnosis, neutrophil recovery in neutropenic patients, and surgical revision of mucormycosis lesions were protective factors. Although not reaching significance on multivariable analysis, visualization of CCT-matching lesions on CXR was associated with significantly increased 84-day mortality (log-rank test, p = 0.033), possibly as a surrogate of extensive lesions and tissue necrosis. This observation supports the exploration of radiologic lesion kinetics as a prognostic staging tool in IPM patients.

Usefulness of 18F-FDG PET-CT in the Management of Febrile Neutropenia: A Retrospective Cohort from a Tertiary University Hospital and a Systematic Review

Febrile neutropenia (FN) is a complication of hematologic malignancy therapy. An early diagnosis would allow optimization of antimicrobials. The 18F-FDG-PET-CT may be useful; however, its role is not well established. We analyzed retrospectively patients with hematological malignancies who underwent 18F-FDG-PET-CT as part of FN management in our university hospital and compared with conventional imaging. In addition, we performed a systematic review of the literature assessing the usefulness of 18F-FDG-PET-CT in FN. A total of 24 cases of FN underwent 18F-FDG-PET-CT. In addition, 92% had conventional CT. In 5/24 episodes (21%), the fever was of infectious etiology: two were bacterial, two were fungal, and one was parasitic. When compared with conventional imaging, 18F-FDG-PET-CT had an added value in 20 cases (83%): it diagnosed a new site of infection in 4 patients (17%), excluded infection in 16 (67%), and helped modify antimicrobials in 16 (67%). Antimicrobials could be discontinued in 10 (41.6%). We identified seven publications of low quality and one randomized trial. Our results support those of the literature. The available data suggest that 18F-FDG-PET-CT is useful in the management of FN, especially to diagnose fungal infections and rationalize antimicrobials. This review points out the low level of evidence and indicates the gaps in knowledge.

Adoption value of support vector machine algorithm-based computed tomography imaging in the diagnosis of secondary pulmonary fungal infections in patients with malignant hematological disorders

This study aimed to assess the feasibility of diagnosing secondary pulmonary fungal infections (PFIs) in patients with hematological malignancies (HM) using computerized tomography (CT) imaging and a support vector machine (SVM) algorithm. A total of 100 patients with HM complicated by secondary PFI underwent CT scans, and they were included in the training group. Concurrently, 80 patients with the same underlying disease who were treated at our institution were included in the test group. The types of pathogens among different PFI patients and the CT imaging features were compared. Radiomic features were extracted from the CT imaging data of patients, and a diagnostic SVM model was constructed by integrating these features with clinical characteristics. Aspergillus was the most common pathogen responsible for PFIs, followed by Candida, Pneumocystis jirovecii, Mucor, and Cryptococcus, in descending order of occurrence. Patients typically exhibited bilateral diffuse lung lesions. Within the SVM algorithm model, six radiomic features, namely the square root of the inverse covariance of the gray-level co-occurrence matrix (square root IV), the square root of the inverse covariance of the gray-level co-occurrence matrix, and small dependency low gray-level emphasis, significantly influenced the diagnosis of secondary PFIs in patients with HM. The area under the curve values for the training and test sets were 0.902 and 0.891, respectively. Therefore, CT images based on the SVM algorithm demonstrated robust predictive capability in diagnosing secondary PFIs in conjunction with HM.

Approach to diagnostic evaluation and prevention of invasive fungal disease in patients prior to allogeneic hematopoietic stem cell transplant

In recent years, advancements in the treatment landscape for hematological malignancies, such as acute myeloid leukemia and acute lymphoblastic leukemia, have significantly improved disease prognosis and overall survival. However, the treatment landscape is changing and the emergence of targeted oral therapies and immune-based treatments has brought forth new challenges in evaluating and preventing invasive fungal diseases (IFDs). IFD disproportionately affects immunocompromised hosts, particularly those undergoing therapy for acute leukemia and allogeneic hematopoietic stem cell transplant. This review aims to provide a comprehensive overview of the pretransplant workup, identification, and prevention of IFD in patients with hematological malignancy. The pretransplant period offers a critical window to assess each patient's risk factors and implement appropriate prophylactic measures. Risk assessment includes evaluation of disease, host, prior treatments, and environmental factors, allowing a dynamic evaluation that considers disease progression and treatment course. Diagnostic screening, involving various biomarkers and radiological modalities, plays a crucial role in early detection of IFD. Antifungal prophylaxis choice is based on available evidence as well as individual risk assessment, potential for drug-drug interactions, toxicity, and patient adherence. Therapeutic drug monitoring ensures effective antifungal stewardship and optimal treatment. Patient education and counselling are vital in minimizing environmental exposures to fungal pathogens and promoting medication adherence. A well-structured and individualized approach, encompassing risk assessment, prophylaxis, surveillance, and patient education, is essential for effectively preventing IFD in hematological malignancies, ultimately leading to improved patient outcomes and overall survival.