Association of Tumor [18F]FDG Activity and Diffusion Restriction with Clinical Outcomes of Rhabdomyosarcomas

Mol Imaging Biol. 2019 Jun;21(3):591-598. doi: 10.1007/s11307-018-1272-1.


Purpose: To evaluate whether the extent of restricted diffusion and 2-deoxy-2-[18F] fluoro-D-glucose ([18F]FDG) uptake of pediatric rhabdomyosarcomas (RMS) on positron emission tomography (PET)/magnetic resonance (MR) images provides prognostic information.

Procedure: In a retrospective, IRB-approved study, we evaluated [18F]FDG PET/CT and diffusion-weighted (DW) MR imaging studies of 21 children and adolescents (age 1-20 years) with RMS of the head and neck. [18F]FDG PET and DW MR scans at the time of the initial tumor diagnosis were fused using MIM software. Quantitative measures of the tumor mass with restricted diffusion, [18F]FDG hypermetabolism, or both were dichotomized at the median and tested for significance using Gray's test. Data were analyzed using a survival analysis and competing risk model with death as the competing risk.

Results: [18F]FDG PET/MR images demonstrated a mismatch between tumor areas with increased [18F]FDG uptake and restricted diffusion. The DWI, PET, and DWI + PET tumor volumes were dichotomized at their median values, 23.7, 16.4, and 9.5 cm3, respectively, and were used to estimate survival. DWI, PET, and DWI + PET overlap tumor volumes above the cutoff values were associated with tumor recurrence, regardless of post therapy COG stage (p = 0.007, p = 0.04, and p = 0.07, respectively).

Conclusion: The extent of restricted diffusion within RMS and overlap of hypermetabolism plus restricted diffusion predict unfavorable clinical outcomes.

Keywords: Diffusion-weighted MR; PET/MR; Rhabdomyosarcoma; [18F]FDG.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Diffusion Magnetic Resonance Imaging*
  • Fluorodeoxyglucose F18 / chemistry*
  • Humans
  • Infant
  • Positron-Emission Tomography
  • Predictive Value of Tests
  • Rhabdomyosarcoma / diagnostic imaging*
  • Rhabdomyosarcoma / pathology
  • Rhabdomyosarcoma / therapy*
  • Treatment Outcome
  • Tumor Burden
  • Young Adult


  • Fluorodeoxyglucose F18