Alexis Leigh Crawley MD, Presenter: Nothing to Disclose

Christopher Klenk MD, Abstract Co-Author: Nothing to Disclose

Andrew Quon MD, Abstract Co-Author: Nothing to Disclose

Daniel L. Rubin MD, MS, Abstract Co-Author: Nothing to Disclose

Heike E. Daldrup-Link MD, Abstract Co-Author: Nothing to Disclose

The overall survival for pediatric patients with soft tissue sarcomas and metastatic disease continues to be less than 30%. New prognostic factors are desperately needed in these patients.  No current imaging evaluation is predictive of tumor histopathology, therapy response or overall outcome which is needed to help determine patient therapy. The purpose of our study was to evaluate, if diffusion-weighted MR scans of pediatric soft tissue sarcomas provide complementary or equivalent information compared to 18F-FDG-PET scans.

We retrospectively evaluated imaging studies of 21 children (age 1-20 years) with alveolar (n=6) and embryonal (n=15) rhabdomyosarcomas who had undergone an 18F-FDG PET/CT and a magnetic resonance (MR) imaging scan with diffusion weighted (DW) sequences within an interval of less than three weeks for initial tumor staging. 18F-FDG PET and DWI scans were fused using MIM software. Areas of increased tumor FDG-uptake, restricted diffusion and the whole tumor on anatomical MR were outlined on each slide and the relative tumor volume that showed increased FDG avidity, restricted diffusion or both was calculated. All data were compared for statistically significant differences using a Wilcoxon signed-rank test and a p<0.05.

All evaluated tumors demonstrated marked heterogeneity. Fused 18F-FDG PET/DW MR images demonstrated significant mismatch of tumor areas with increased 18F-FDG uptake and restricted diffusion. The average volume of restricted diffusion corresponded to 88% +/- 22% of tumor volume, average volume FDG avidity corresponded to 64% +/- 30% of the tumor volume, and average volume of tumor that demonstrated both corresponded to 45% +/-23% of the tumor volume. None of the quantitative imaging data showed significant differences between alveolar and embryonal RMS. Follow up imaging at week 15 demonstrated progressive disease in one patient which also demonstrated the greatest percentage of FDG and diffusion restriction overlap (97%).

DW MR scans of pediatric soft tissue sarcomas provide complementary or equivalent information compared to 18F-FDG-PET scans. Our ongoing studies evaluate, if the above mentioned parameters can be used to differentiate responders and non-responders to chemotherapy.

FDG and diffusion restriction provide complimentary information and may be used to differentiate responders and non-responders to chemotherapy.

Crawley, A, Klenk, C, Quon, A, Rubin, D, Daldrup-Link, H, Correlation of 18F FDG Activity and Diffusion Restriction of Rhabdomyosarcomas on PET/MR: Potential Additional Prognostic Factors.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019731.html