18F-FDG PET/MRI for Staging and Interim Response Assessment in Pediatric and Adolescent Hodgkin Lymphoma: A Prospective Study with 18F-FDG PET/CT as the Reference Standard

Abstract

Treatment regimens for pediatric Hodgkin lymphoma (HL) depend on accurate staging and treatment response assessment, based on accurate disease distribution and metabolic activity depiction. With the aim of radiation dose reduction, we compared the diagnostic performance of ¹⁸F-FDG PET/MRI with a ¹⁸F-FDG PET/CT reference standard for staging and response assessment. Methods: Twenty-four patients (mean age, 15.4 y; range, 8-19.5 y) with histologically proven HL were prospectively and consecutively recruited in 2015 and 2016, undergoing both ¹⁸F-FDG PET/CT and ¹⁸F-FDG PET/MRI at initial staging (n = 24) and at response assessment (n = 21). The diagnostic accuracy of ¹⁸F-FDG PET/MRI for both nodal and extranodal disease was compared with that of ¹⁸F-FDG PET/CT, which was considered the reference standard. Discrepancies were retrospectively classified as perceptual or technical errors, and ¹⁸F-FDG PET/MRI and ¹⁸F-FDG PET/CT were corrected by removing perceptual error. Agreement with Ann Arbor staging and Deauville grading was also assessed. Results: For nodal and extranodal sites combined, corrected staging ¹⁸F-FDG PET/MRI sensitivity was 100% (95% CI, 96.7%-100%) and specificity was 99.5% (95% CI, 98.3%-99.9%). Corrected response-assessment ¹⁸F-FDG PET/MRI sensitivity was 83.3% (95% CI, 36.5%-99.1%) and specificity was 100% (95% CI, 99.2%-100%). Modified Ann Arbor staging agreement between ¹⁸F-FDG PET/CT and ¹⁸F-FDG PET/MRI was perfect (κ = 1.0, P = 0.000). Deauville grading agreement between ¹⁸F-FDG PET/MRI and ¹⁸F-FDG PET/CT was excellent (κ = 0.835, P = 0.000). Conclusion:¹⁸F-FDG PET/MRI is a promising alternative to ¹⁸F-FDG PET/CT for staging and response assessment in children with HL.

Keywords: Hodgkin lymphoma; PET/CT; PET/MRI; pediatric; staging.

Graphical abstract

FIGURE 1.

Study flowchart.

FIGURE 2.

Axial CT (A), ¹⁸F-FDG PET (B), ¹⁸F-FDG PET/CT (C), T2-HASTE MRI (D), ¹⁸F-FDG PET (E), and ¹⁸F-FDG PET/MRI (F) images showing concordant (indicating that PET/CT and PET/MRI show the same lesion) upper right deep cervical lymphadenopathy (arrows) in a 12-y-old boy with lymphocyte-predominant HL at staging.

FIGURE 3.

(A–C) Coronal STIR (A), ¹⁸F-FDG PET (B), and ¹⁸F-FDG PET/MR (C) images demonstrating lymphadenopathy in right supraclavicular fossa and right paratracheal region and nodule in right lung (arrows) in a 14-y-old boy with HL. (D–F) Early response assessment after 2 cycles of chemotherapy showing residual smaller lymphadenopathy in the right supraclavicular fossa on coronal STIR image (D) and no uptake on coronal ¹⁸F-FDG PET (E) or ¹⁸F-FDG PET/MRI (F) (arrows). Other sites of disease have resolved.