Whole-body MR imaging with the use of parallel imaging for detection of skeletal metastases in pediatric patients with small-cell neoplasms: comparison with skeletal scintigraphy and FDG PET/CT

Abstract

Background In pediatric patients with small-cell tumors, there is an increasing demand for accurate and early detection of skeletal, especially bone marrow, metastases as new treatment protocols are introduced. Whole-body MR imaging (WB-MR) and 18F-fluorodeoxyglucose PET/CT (FDG PET/CT) are new promising imaging methods that can detect metastases before osteoblastic host response occurs, which is the basis for detection of metastases by skeletal scintigraphy (SSC). Objective To assess the ability of WB-MR to detect marrow metastases in children with small-cell neoplasms and compare its performance with that of FDG PET/CT and SSC. Materials and methods During a 16-month period, 26 children and adolescents with histopathologically proven small-cell neoplasms underwent WB-MR, FDG PET/CT and Tc-phosphonate-based SSC in a random order within a 25-day period. Metastases were localized in relation to eight regions of the body. Results WB-MR revealed metastases in 39 out of a total of 208 regions in 26 patients (sensitivity 97.5%, specificity 99.4%, positive predictive value 97.5%, negative predictive value 99.4%), SSC in 12 regions (sensitivity 30%, specificity 99.4%, PPV 92.3%, NPV 85.6%) and FDG PET/CT in 36 regions (sensitivity 90.0%, specificity 100%, PPV 100%, NPV 97.7%). Both WB-MR and FDG PET/CT showed excellent agreement (kappa) with the final diagnosis (96.9% and 93.6% respectively), whereas SSC showed only moderate agreement (39.6%). Conclusion Our results suggest that WB-MR and FDG PET/CT studies are robust imaging modalities for screening for skeletal metastases, and are far more accurate than SSC. The lack of radiation is an additional advantage of WB-MR, especially in the pediatric population.