Beyond biomarkers: How enhanced CT imaging can improve the diagnostic-driven management of invasive mould disease

Abstract

CT imaging remains an essential diagnostic test for identification, staging and management of invasive mould infection (IMI) in patients with hematological malignancies. Yet the limited specificity of standard CT imaging can drive excessive antifungal use in patients, especially when more definitive diagnosis cannot be established through microbiology or invasive diagnostic procedures. CT pulmonary angiography (CTPA) is a complimentary, non-invasive approach to standard CT that allows for direct visualization of pulmonary arteries inside infiltrates for signs of angioinvasion, vessel destruction and vessel occlusion. Experience from several centers that are using CTPA as part of a standard diagnostic protocol for IMI suggests that a positive vessel occlusion sign (VOS) is the most sensitive and a specific sign of IMI in both neutropenic and non-neutropenic patients. CTPA is particularly useful in patients who develop suspected breakthrough IMI during antifungal prophylaxis because, unlike serum and/or BAL galactomannan and polymerase chain reaction (PCR) testing, the sensitivity is not reduced by antifungal therapy. A negative VOS may also largely rule-out the presence of IMI, supporting earlier discontinuation of empirical therapy. Future imaging protocols for IMI in patients with hematological malignancies will likely replace standard chest X-rays in favor of early low radiation dose CT exams for screening, with characterization of the lesions by CTPA and routine follow-up using functional/metabolic imaging such as 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (FDG-PET/CT) to assess treatment response. Hence, enhanced CT imaging techniques can improve the diagnostic-driven management of IMI management in high-risk patients with hematological malignancies.

Keywords: computed tomography pulmonary angiography; hematological malignancies; invasive mould disease; positron emission tomography.