Diagnostic value of combined 18F-FDG PET/MRI for staging and restaging in paediatric oncology

Purpose

The present study compares the diagnostic value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and MRI to combined/registered ¹⁸F-FDG PET/MRI for staging and restaging in paediatric oncology.

Methods

Over 8?years and 2?months, 270 ¹⁸F-FDG PET and 270 MRI examinations (mean interval 5?days) were performed in 132 patients with proven (n?=?117) or suspected (n?=?15) malignant disease: solid tumours (n?=?64), systemic malignancy (n?=?53) and benign disease (n?=?15). A total of 259 suspected tumour lesions were analysed retrospectively during primary diagnosis and 554 lesions during follow-up. Image analysis was performed separately on each modality, followed by analysis of combined and registered ¹⁸F-FDG PET/MRI imaging.

Results

A total of 813 lesions were evaluated and confirmed by histopathology (n?=?158) and/or imaging follow-up (n?=?655) after 6?months. In the separate analysis of ¹⁸F-FDG PET and MRI, sensitivity was 86?%/94?% and specificity 85?%/38?%. Combined/registered ¹⁸F-FDG PET/MRI led to a sensitivity of 97?%/97?% and specificity of 81?%/82?%. False-positive results (¹⁸F-FDG PET n?=?69, MRI n?=?281, combined ¹⁸F-FDG PET/MRI n?=?85, registered ¹⁸F-FDG PET/MRI n?=?80) were due to physiological uptake or post-therapeutic changes. False-negative results (¹⁸F-FDG PET n?=?50, MRI n?=?20, combined ¹⁸F-FDG PET/MRI n?=?11, registered ¹⁸F-FDG PET/MRI n?=?11) were based on low uptake or minimal morphological changes. Examination-based evaluation during follow-up showed a sensitivity/specificity of 91?%/81?% for ¹⁸F-FDG PET, 93?%/30?% for MRI and 96?%/72?% for combined ¹⁸F-FDG PET/MRI.

Conclusion

For the detection of single tumour lesions, registered ¹⁸F-FDG PET/MRI proved to be the methodology of choice for adequate tumour staging. In the examination-based evaluation, MRI alone performed better than ¹⁸F-FDG PET and combined/registered imaging during primary diagnosis. At follow-up, however, the examination-based evaluation demonstrated a superiority of ¹⁸F-FDG PET alone.