FDG PET/CT outperforms diagnostic CT in the initial staging of non Hodgkin's lymphoma (NHL) in pediatric patients

Objectives This study was to assess the role of FDG PET/CT in the initial staging of NHL in pediatric patients.

Methods Materials and methods: Fifteen patients (average age: 14.1 years old) had FDG PET/CT at diagnosis with a diagnostic contrast CT within a week of PET/CT prior to any therapy were included in this retrospective study. The findings of PET/CT were correlated with diagnostic contrast CT for evaluating 16 nodal and 4 extranodal (lung, spleen, liver, and bone marrow) regions per patient for presence of NHL.

Results Per lesion analysis showed that PET/CT and diagnostic CT were concordant in 57.6% of the lesions. Fifty seven disease sites were detected by PET/CT of which 18 were overlooked by diagnostic contrast CT. On the CT part, 49 disease sites were identified, of which 7 were negative on PET/CT imaging. Five patients were upstaged using PET/CT as compared to diagnostic CT (two from stage I to IV; two from stage II to IV; and one stage II case on PET/CT but was negative on diagnostic CT). Among the five patients upstaged by PET/CT, three had bone marrow lesions and one had liver involvement detected only by PET/CT, and another patient had positive mediastinal /hilar nodes and spleen involvement on PET/CT but these regions were within normal limits on diagnostic CT scan.

Conclusions PET/CT outperformed diagnostic CT imaging in the initial staging of NHL in pediatric population (especially in detecting bone marrow lesions) with upstaging in one-third of all patients included in our investigation.