1. MULTI-MODALITY IMAGING OF PREOPERATIVELY IRRADIATED SARCOMA PATIENTS DOES NOT PREDICT PATHOLOGICAL OUTCOME. Rick Haas Luc Dewit, Frits van Coevorden, Hans Peterse, Claudette Loo, Renato Valdés Olmos NKI – AVL Amsterdam

2. MULTI-MODALITY IMAGING OF PREOPERATIVELY IRRADIATED SARCOMA PATIENTS DOES NOT PREDICT PATHOLOGICAL OUTCOME. …..or does it…..????

3. Objectives & Purpose Statement: Often treatment outcome can be predicted by specific imaging modalities. Sometimes very early after treatment initiation. (FDG-PET in imatinib treated GIST patients)

4. Objectives & Purpose Statement: Often treatment outcome can be predicted by specific imaging modalities. Sometimes very early after treatment initiation. (FDG-PET in imatinib treated GIST patients) Questions: Are imaging modalities able to predict radiation outcome in preoperatively irradiated sarcoma patients. And if so; which modality performs best.

5. Patients & Methods 15 patients received preoperative irradiation (50 Gy in 5 weeks) in various sarcoma subtypes. Baseline investigations: Pathology MRI CT FDG-PET Reevaluation: 4 weeks after radiotherapy

6. Patients & Methods; scoring Pathology:necrosis on biopsy material and the surgical specimen. MRI:necrosis on a 5 step scale tumor measurements CT:Houncefield Units (HU; average number over tumor volume) FDG-PET:SUV max SUV mean Note:pathology is “the golden standard”

7. Results(I) Necrosis is adequately predicted by modality % of cases SUV max 57% SUV mean 43% MRI50% HU 9%

8. Results(II) In 30% of cases volume after irradiation increased (140-236% relative to baseline). Performance of these tests was not significantly better in good responding myxoid liposarcomas patients as compared to other sarcoma subtypes.

9. Pathology

10. The “perfect radiosensitive tumor”

11. The “perfect radioresistent tumor”

12. Patients in this study

13. First Conclusions Multi-modality imaging in preoperatively irradiated sarcoma patients in this population did not adequately predict pathology outcome. Induction of necrosis and increase in volume is a common phenomenon. More patients and longer follow-up on local control is needed to fully appreciate the most appropriate imaging modality.

14. However…… Suppose you would consider a boost of 10Gy if 50Gy would not induce necrosis. Prerequisites: adequately define necrotic tumors after 50Gy enough is enough => no need of boost adequately define vital tumors after 50Gy don’t deny these patients a boost

15. However…… Suppose you would consider a boost of 10Gy if 50Gy would not induce necrosis. By ROC-curve analysis using a SUV max-preRT of 4.5 as a cut-off value Than: In 100% of cases necrosis correctly identified: 50Gy = enough; no boost

16. However…… Suppose you would consider a boost of 10Gy if 50Gy would not induce necrosis. By ROC-curve analysis using a SUV max-preRT of 4.5 as a cut-off value Than: In 100% of cases necrosis correctly identified: 50Gy = enough; no boost In 75% of cases vital tumor correctly identified: you "win" 75% of your patients who might need a boost at no loss of patients who get more RT, while not necessary

17. Final conclusions More patients and longer follow-up on local control is needed to fully appreciate the most appropriate imaging modality. Probably SUV max-preRT

18. Final conclusions More patients and longer follow-up on local control is needed to fully appreciate the most appropriate imaging modality. Probably SUV max-preRT This will be part of a new EORTC STBSG / ROG phase III trial. EORTC 6207NN / 2207NN