Background/Objectives: The main objective of this proof-of-concept study is to assess the clinical impact of microbial cell-free DNA (mcfDNA) surveillance in neutropenic patients diagnosed with acute myeloid leukemia (AML) undergoing chemotherapy in the outpatient setting. Neutropenia is a common complication in this patient cohort and enhances the risk of fatal opportunistic bacterial and fungal infections. Accurate and timely diagnosis of these infections in outpatient asymptomatic individuals is critical. The identification of infectious pathogens in a sub-clinical state has the potential to permit adjustment and escalation of anti-infective therapy for the prevention of clinical deterioration and improved clinical outcomes.

Methods: Fourteen neutropenic patients were studied in this prospective observational case series who were receiving outpatient consolidation chemotherapy for AML. Traditional blood cultures (BCs) were obtained when clinically indicated and blood samples were collected for plasma mcfDNA metagenomic sequencing up to two times a week at outpatient oncology appointments. Results between mcfDNA and the standard microbiology laboratory were compared for identified infectious agents. To determine the clinical impact of detected pathogens in the outpatient setting, we performed clinical adjudication. Seven adjudicators, all practicing in Transplant Infectious Diseases, Leukemia, and Microbiology Laboratory specialists, met five times between June 2024 and April 2025. There were at least three attendees present at each meeting.

Results: Standard microbiologic testing demonstrated that blood cultures identified pathogens in only two patients, despite several cases where infection was suspected. In contrast, mcfDNA testing detected invasive microbes in 11of the 14patients, including bacteria, such as Staphylococcus aureus, and fungal pathogens, such as Candida and Aspergillus species, and Pneumocystis jirovecii. These results were derived from the adjudication of 551 administered surveys. There were 31 decisions to broaden antimicrobial responses and a single decision to apply a narrower antimicrobial response. All other responses were no change to antimicrobials. At the 4-month mark, 13 outpatients remained alive, and one subject had died.

Conclusions: In the outpatient setting, mcfDNA surveillance was clinically adjudicated, resulting in actionable antimicrobial therapeutic adjustments. These data demonstrate that mcfDNA offers a more rapid, reliable method for detecting pathogens in at-risk immunocompromised individuals receiving chemotherapy in the outpatient setting. Clinical trials will be required to confirm the potential impact of mcfDNA surveillance in an outpatient setting to guide more accurate treatment decisions and improve patient outcomes with neutropenia.

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2025
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