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CTOS 14.11.08 Soft Tissue Sarcoma of the Extremity Comparison of Conformal Post-operative Radiotherapy (CRT) and Intensi PowerPoint Presentation
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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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slide1

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

slide2

CRT and IMRT for extremity STS

  • Background
  • Materials and Methods
  • Results
  • Summary
slide3

CRT and IMRT for extremity STS

  • Background
  • Materials and Methods
  • Results
  • Summary
slide4

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
slide5
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
slide6

CRT and IMRT for extremity STS

  • Background
  • Materials and Methods
  • Results
  • Summary
patient data
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
target volume definition
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
slide10

whole femur

neurovascular bundle

PTV2

PTV1

tissue corridor

Organ definition

normal tissue outside PTV1

radiotherapy planning
Radiotherapy planning
  • Primary planning objective
    • PTV dose
    • femur
    • skin corridor
  • Other planning objectives
    • neurovascular bundle
    • soft tissue outside PTV
dose prescription
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)
analysis
Analysis
  • cumulative dose volume histograms (DVH)
  • Dmean, Dmax, Dmin
  • Conformity Index (CI)
  • Heterogeneity Index (HI)
slide14

CRT and IMRT for extremity STS

  • Background
  • Materials and Methods
  • Results
  • Summary
slide15

Conformal Radiotherapy

2-3 field (simple) IMRT

4-5 field IMRT

slide16

sagittal view

conformal

4-5f IMRT

2-3f

slide17

coronal view

conformal

2-3f IMRT

4-5f IMRT

simple 2 3f imrt
‘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)
slide21

CRT and IMRT for extremity STS

  • Background
  • Materials and Methods
  • Results
  • Summary
summary
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
slide23

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
slide24

Acknowledgment

Radiotherapy Department

Royal Marsden NHS Foundation Trust