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CTOS 14.11.08 Soft Tissue Sarcoma of the Extremity Comparison of Conformal Post-operative Radiotherapy (CRT) and Intensi

CTOS 14.11.08 Soft Tissue Sarcoma of the Extremity Comparison of Conformal Post-operative Radiotherapy (CRT) and Intensity Modulated Radiotherapy (IMRT). Young K Lee 1 , Alexandra J Stewart 2 , Frank H Saran 3.

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CTOS 14.11.08 Soft Tissue Sarcoma of the Extremity Comparison of Conformal Post-operative Radiotherapy (CRT) and Intensi

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  1. CTOS 14.11.08 Soft Tissue Sarcoma of the Extremity Comparison of Conformal Post-operative Radiotherapy (CRT) and Intensity Modulated Radiotherapy (IMRT) Young K Lee1, Alexandra J Stewart2,Frank H Saran3 1Joint Department of Physics, Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK 2St Luke’s Cancer Centre, Royal Surrey County Hospital, Guildford, Surrey, UK 3Department of Radiotherapy, Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK

  2. CRT and IMRT for extremity STS • Background • Materials and Methods • Results • Summary

  3. CRT and IMRT for extremity STS • Background • Materials and Methods • Results • Summary

  4. Background • Limb-sparing surgery in combination with focal radiotherapy - standard of care in patients with intermediate and high grade limb and limb girdle soft tissue sarcomas (STS) • Normal tissue toxicity increases with escalating total and integral dose • Dose prescription limited by organs-at-risk (OAR) surrounding the PTV

  5. Aims • To define a reproducible and comparable target volume definition for CT planning • To define reproducible prospective planning dose volume constraints • To assess the ability of inversely-planned IMRT plans to minimise the dose to surrounding OAR • To assess efficacy of ‘simple’ IMRT compared to ‘complex’ IMRT planning

  6. CRT and IMRT for extremity STS • Background • Materials and Methods • Results • Summary

  7. Patient data • T2 and G2/3 STS of the thigh (n=10) • No tumours invading bone • Entire surgical scar and all drain sites marked • Planning CT scan (GE HiSpeed QX/i, Milwaukee, WI) • pelvic brim to below knee • customised immobilisation • slice thickness = 2.5mm

  8. Target volume definition • Phase I volume PTV1 = tumour bed + 5cm SI and 3cm circumferentially • Phase II volume PTV2 = tumour bed + 2cm isotropically • OAR defined as whole femur, neurovascular bundle, normal tissue corridor and normal tissue outside PTV1

  9. Planning target volumes PTV1 PTV2

  10. whole femur neurovascular bundle PTV2 PTV1 tissue corridor Organ definition normal tissue outside PTV1

  11. Radiotherapy planning • Primary planning objective • PTV dose • femur • skin corridor • Other planning objectives • neurovascular bundle • soft tissue outside PTV

  12. Dose prescription • Pinnacle3 v7.4f (Philips Radiation Oncology Systems, Madison, WI) • 2-phase 3D-CRT • Ph I - 50 Gy/25# (5 weeks) • Ph II - 16 Gy/8# (1½ weeks) • IMRT with simultaneous integrated boost (SIB) • Ph I - 50 Gy/25# (5 weeks) • Ph II - 62.5 Gy/25# (5 weeks) (/ = 10 Gy)

  13. Analysis • cumulative dose volume histograms (DVH) • Dmean, Dmax, Dmin • Conformity Index (CI) • Heterogeneity Index (HI)

  14. CRT and IMRT for extremity STS • Background • Materials and Methods • Results • Summary

  15. Conformal Radiotherapy 2-3 field (simple) IMRT 4-5 field IMRT

  16. sagittal view conformal 4-5f IMRT 2-3f

  17. coronal view conformal 2-3f IMRT 4-5f IMRT

  18. Conformity and Heterogeneity

  19. DVH summary

  20. ‘Simple’ 2-3f IMRT? • Median number of segments • 26 (range 13-37) for 2-3f IMRT • 36 (range 34-56) for 4-5f IMRT • Both IMRT plans were more conformal and less heterogeneous than 3D-CRT • Both IMRT delivered significantly lower femur V45 compared to 3D-CRT plans • HOWEVER, 4/5f IMRT resulted in significantly lower femur V45 when compared directly to 2/3f IMRT (p=0.04)

  21. CRT and IMRT for extremity STS • Background • Materials and Methods • Results • Summary

  22. Summary • Reproducible, comprehensive planning guidelines and dose-volume constraints for 3D planning for extremity sarcomas devised • 4/5f IMRT plan - lowest clinically relevant doses to OAR whilst delivering conformal doses to PTV • Large primary tumour • 4/5f preferable to a 2/3f IMRT approach • Small, superficial disease • 3D-CRT may provide adequate treatment without added cost and complexity

  23. Further work • Results from this study may not be directly translated to all other primary locations of STS of the extremity • IMRT approach should be assessed prospectively with respect to late toxicity within the confines of a prospective clinical trial

  24. Acknowledgment Radiotherapy Department Royal Marsden NHS Foundation Trust

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