A survey on the institutional practices of the use of isavuconazole in onco-hematological children, on behalf of the Infectious Working Group of AIEOP.

Isavuconazole is a broad-spectrum antifungal agent approved for the treatment of invasive fungal infections (IFIs) in adults and, recently, in pediatric patients aged 1 year and older. Use in the pediatric setting remains limited, but available data indicate generally favorable safety and efficacy. This survey describes the institutional practices of use of isavuconazole across centers belonging to the Italian Association of Pediatric Hematology and Oncology (AIEOP). A 25-item web-based questionnaire, approved by the scientific board of the Infectious Working Group, was distributed to AIEOP centers between December 2024 and January 2025. The survey covered indications (prophylaxis and treatment), formulations and dosing, therapeutic drug monitoring (TDM), drug-drug interactions, and management of adverse events. In 22/49 (45%) responding centers, isavuconazole was available as capsules in 20/22 (91%) and as an intravenous formulation in 17/22 (77%). Primary prophylaxis was reported in 2/22 (9%), while secondary prophylaxis was reported in 12/22 (55%) centers, in patients diagnosed with possible (10/22, 45%) or probable (12/22, 55%) IFIs. In cases of Aspergillus spp. infection, 4/22 (18%) centers considered isavuconazole for first-line treatment, 14/22 (64%) for salvage treatment, and 5/22 (23%) for combination treatment. In cases of mucormycosis, 4/22 (18%) considered isavuconazole for first-line treatment, 9/22 (41%) for salvage treatment, and 5/22 (23%) for combination treatment. TDM was commonly adopted but varied across centers: 7/22 (32%) performed TDM between days 5 and 7, 4/22 (18%) only after the loading dose, and 5/22 (23%) did not perform TDM.Conclusion: The results of this study show a widespread, off-label, heterogeneous use of isavuconazole in AIEOP centers. Such variability indicates the need for more standardized indications, dosages, and monitoring strategies. What is known? • Isavuconazole is approved for invasive fungal infections in adults and, recently, in children aged =1 year, with favorable safety and efficacy, although pediatric experience remains limited. • Real-world use of isavuconazole in pediatric hematology-oncology has not been systematically described. What is new? • This national AIEOP survey shows widespread but heterogeneous use of isavuconazole, mainly as secondary prophylaxis and salvage therapy, with inconsistent therapeutic drug monitoring. • Standardized indications, dosing, and monitoring strategies are needed in pediatric onco-hematology.