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

CTOS 14.11.08CTOS 14.11.08

Soft Tissue Sarcoma of the Extremity

Comparison of Conformal Post-operative Comparison of Conformal Post-operative Radiotherapy (CRT) and Intensity Modulated Radiotherapy (CRT) and Intensity Modulated

Radiotherapy (IMRT)Radiotherapy (IMRT)

1Joint Department of Physics, Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK2St Luke’s Cancer Centre, Royal Surrey County Hospital, Guildford, Surrey, UK3Department of Radiotherapy, Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK

Young K Lee1, Alexandra J Stewart2, Frank H Saran3

BackgroundBackground

Materials and MethodsMaterials and Methods

ResultsResults

SummarySummary

CRT and IMRT for extremity STSCRT and IMRT for extremity STS



ResultsResults

SummarySummary



Limb-sparing surgery in combination with focal Limb-sparing surgery in combination with focal radiotherapy - standard of care in patients with radiotherapy - standard of care in patients with intermediate and high grade limb and limb girdle intermediate and high grade limb and limb girdle soft tissue sarcomas (STS)soft tissue sarcomas (STS)

Normal tissue toxicity increases with escalating Normal tissue toxicity increases with escalating total and integral dosetotal and integral dose

Dose prescription limited by organs-at-risk (OAR) Dose prescription limited by organs-at-risk (OAR) surrounding the PTVsurrounding the PTV

AimsAims

To define a reproducible and comparable target To define a reproducible and comparable target volume definition for CT planningvolume definition for CT planning

To define reproducible prospective planning dose To define reproducible prospective planning dose volume constraintsvolume constraints

To assess the ability of inversely-planned IMRT To assess the ability of inversely-planned IMRT plans to minimise the dose to surrounding OARplans to minimise the dose to surrounding OAR

To assess efficacy of ‘simple’ IMRT compared to To assess efficacy of ‘simple’ IMRT compared to ‘complex’ IMRT planning‘complex’ IMRT planning



ResultsResults

SummarySummary


Patient dataPatient data

TT22 and G and G2/32/3 STS of the thigh (n=10) STS of the thigh (n=10)

No tumours invading boneNo tumours invading bone

Entire surgical scar and all drain sites markedEntire surgical scar and all drain sites marked

Planning CT scan Planning CT scan (GE HiSpeed QX/i, Milwaukee, WI)(GE HiSpeed QX/i, Milwaukee, WI)

• pelvic brim to below kneepelvic brim to below knee

• customised immobilisation customised immobilisation

• slice thickness = 2.5mmslice thickness = 2.5mm

Target volume definitionTarget volume definition

Phase I volumePhase I volume

PTVPTV11 = tumour bed + 5cm SI and 3cm = tumour bed + 5cm SI and 3cm

circumferentially circumferentially

Phase II volumePhase II volume

PTVPTV22 = tumour bed + 2cm isotropically = tumour bed + 2cm isotropically

OAR defined as whole femur, neurovascular OAR defined as whole femur, neurovascular bundle, normal tissue corridor and normal tissue bundle, normal tissue corridor and normal tissue outside PTVoutside PTV11

Planning target volumesPlanning target volumes

PTVPTV11

PTVPTV22

normal tissue outside PTV1PTV1

whole femur

PTV2

tissue corridor

neurovascular bundle

Organ definitionOrgan definition

Radiotherapy planningRadiotherapy planning

Primary planning objective

• PTV dose PTV dose

• femur femur

• skin corridorskin corridor

Other planning objectives

• neurovascular bundle

• soft tissue outside PTV

Dose prescriptionDose prescription

PinnaclePinnacle33 v7.4f (Philips Radiation Oncology v7.4f (Philips Radiation Oncology Systems, Madison, WI)Systems, Madison, WI)

2-phase 3D-CRT2-phase 3D-CRT

• Ph I - 50 Gy/25# (5 weeks)Ph I - 50 Gy/25# (5 weeks)

• Ph II - 16 Gy/8# (1½ weeks)Ph II - 16 Gy/8# (1½ weeks)

IMRT with simultaneous integrated boost (SIB)IMRT with simultaneous integrated boost (SIB)

• Ph I - 50 Gy/25# (5 weeks)Ph I - 50 Gy/25# (5 weeks)

• Ph II - 62.5 Gy/25# (5 weeks) Ph II - 62.5 Gy/25# (5 weeks) ((// = 10 Gy) = 10 Gy)

AnalysisAnalysis

cumulative dose volume histograms (DVH) cumulative dose volume histograms (DVH)

DDmeanmean, D, Dmaxmax, D, Dminmin

Conformity Index (CI)Conformity Index (CI)

Heterogeneity Index (HI)Heterogeneity Index (HI)



ResultsResults

SummarySummary


Conformal RadiotherapyConformal Radiotherapy2-3 field (simple) IMRT 2-3 field (simple) IMRT 4-5 field IMRT 4-5 field IMRT

conformalconformal 2-3f2-3f 4-5f IMRT4-5f IMRT

sagittal viewsagittal view

conformalconformal 2-3f IMRT2-3f IMRT 4-5f IMRT4-5f IMRT

coronal viewcoronal view

Conformity and HeterogeneityConformity and Heterogeneity

Mean Conformity

Index (range)p-value

Mean Heterogeneity Index (range)

p-value

3DCRT 1.76(1.48-2.47)

1.052 (1.031-1.065)

2/3f IMRT

1.59(1.15-2.67) 0.02

1.045(1.029-1.063) 0.06

4/5f IMRT

1.33(1.08-1.84) 0.0002

1.036(1.027-1.049) 0.001

DVH summaryDVH summary

‘‘Simple’ 2-3f IMRT?Simple’ 2-3f IMRT?

Median number of segmentsMedian number of segments

• 26 (range 13-37) for 2-3f IMRT26 (range 13-37) for 2-3f IMRT

• 36 (range 34-56) for 4-5f IMRT36 (range 34-56) for 4-5f IMRT

Both IMRT plans were more conformal and less Both IMRT plans were more conformal and less heterogeneous than 3D-CRTheterogeneous than 3D-CRT

Both IMRT delivered significantly lower femur VBoth IMRT delivered significantly lower femur V4545

compared to 3D-CRT planscompared to 3D-CRT plans

HOWEVER, 4/5f IMRT resulted in significantly HOWEVER, 4/5f IMRT resulted in significantly lower femur Vlower femur V4545 when compared directly to 2/3f when compared directly to 2/3f

IMRT (p=0.04)IMRT (p=0.04)



ResultsResults

SummarySummary


SummarySummary

Reproducible, comprehensive planning guidelines Reproducible, comprehensive planning guidelines and dose-volume constraints for 3D planning for and dose-volume constraints for 3D planning for extremity sarcomas devised extremity sarcomas devised

4/5f IMRT plan - lowest clinically relevant doses to 4/5f IMRT plan - lowest clinically relevant doses to OAR whilst delivering conformal doses to PTVOAR whilst delivering conformal doses to PTV

Large primary tumour Large primary tumour

• 4/5f preferable to a 2/3f IMRT approach4/5f preferable to a 2/3f IMRT approach

Small, superficial diseaseSmall, superficial disease

• 3D-CRT may provide adequate treatment without 3D-CRT may provide adequate treatment without added cost and complexityadded cost and complexity

Results from this study may not be directly Results from this study may not be directly translated to all other primary locations of STS of translated to all other primary locations of STS of the extremitythe extremity

IMRT approach should be assessed prospectively IMRT approach should be assessed prospectively with respect to late toxicity within the confines of with respect to late toxicity within the confines of a prospective clinical triala prospective clinical trial

Further workFurther work

Radiotherapy DepartmentRoyal Marsden NHS Foundation Trust

AcknowledgmentAcknowledgment

Documents

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