Lung invasive fungal infection (IFI) in acute myeloid leukemia (AML) patients: role of 18-FDG-PET/CT

Objectives To evaluate the role of FDG PET/CT with respect to conventional CT scan, in acute myeloid leukemia (AML) patients with lung invasive fungal infection (IFI).

Methods 14 patients with AML and suspected lung IFI performed chest CT scan (CT1) followed by PET/CT (PET1) scan, before antimicotic treatment. CT and PET/CT were repeated 2 months after the beginning of treatment (n= 12 pts) and compared to basal evaluations to assess treatment efficacy (CT2, PET2): lesions with the highest FDG uptake on PET was selected as “reference lesion” and SUVmax was calculated for PET1 and PET2. Metabolic response (MR) was measured as follow: complete MR (CMR, uptake ≤ than mediastinal blood-pool), partial MR (PMR, partial reduction of the lesion uptake > than mediastinal blood-pool), progressive disease (PD, increase uptake and/or new lesions).

Results : In 14/14 cases (100%) PET1 and CT1 were positive for IFI. The mean SUV max was 6.5 ± 2.4 (range 3.3-11.8). PET2 (n = 12) showed 4 CMR, 4 PMR, (with a mean reduction of SUVmax 53%), 2 PD and 2 with both PMR of reference lesion and concomitant new PD lung lesions with FDG uptake (PR/PD). In the same group of 10 patients, CT2 was concordant with PET2 in 10/12 cases (83%), while in 2 cases CT2 showed partial reduction of lung lesions and a CMR on PET2. Of the 10 concordant patients, 5 died because of infections (2PMR, 2PD, 1 both PMR/PD), and 5 are alive, median follow-up 356 days from PET/CT1, (2 CR, 2 PR and 1 PR/PD). Of the 2 discordant patients 1 died because of sepsis, and 1 patient is on follow-up (150 days).

Conclusions PET/CT scan can help in monitoring treatment efficacy of IFI in AML patient. However, as PET/CT and CT were concordant in 83% of cases (10/12), while in 2 cases PET/CT showed a complete metabolic response in a persistent lung lesion at CT, these preliminary data cannot support a relevant additional role of PET with respect to CT scan; further follow-up and larger studies are needed.