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Retroperitoneal Sarcoma (RPS) High Risk Gross Tumor Volume Boost
(HR GTV Boost) Contour Delineation Agreement among RTOG Sarcoma Radiation and Surgical Oncologists
Elizabeth H Baldini MD, MPHDana-Farber Cancer Institute/Brigham and Women’s Hospital
CTOSOctober 16, 2014
Contributing Authors
E Baldini, C Raut
D Wang, R Abrams, K Millikan
K Salerno, J Kane
C Deville, G Karakousis
I Petersen, M Kendrick
T DeLaney, Y Chen, J Mullen
W Bosch
Dana-Farber/Brigham & Women’s
Rush University Medical Center
Roswell Park Cancer Institute
University of Pennsylvania
Mayo Clinic
Massachusetts General Hospital
Washington University
Supported by grants U10CA21661, U10CA180868, U10CA180822, U10CA37422, U24CA180803 from the National Cancer Institute
Background
• Only proven curative intent treatment modality for RPS is surgery
• Role of pre-op RT has not been proven and is the subject of a randomized trial: EORTC STRASS 62092
• In the meantime, many multi-disciplinary teams employ pre-op RT for RPS and consensus guidelines have been developed for delineation of RT target volumes*
*CTOS, New York, 2013
Background
• Further, there is interest in delivering a “boost” dose of RT to high risk areas of the tumor volume judged to be at risk for positive margins following resection
– This is being tested in a multi-center Phase I/II trial among several US NRG institutions (PI: DeLaney)
Gross TumorVolume(GTV)
High Risk Boost Volume
Radiation Target Volume Definitions
• GTV: Gross Tumor Volume
• CTV: Clinical Target Volume- GTV plus adjacent areas of potential microscopic disease
• High Risk GTV (HR GTV): Area of GTV judged to be at high risk of positive margins after resection
GTV: redCTV: yellow
GTV: redHR GTV: pink
Background
Target Volume Kappa Agreement
RPS1 RPS2
Gross Tumor Volume(GTV)
0.84 Almost Perfect 0.92 Almost Perfect
Clinical Target Volume(CTV)
0.79 Substantial 0.86 Almost Perfect
HR Boost Volume 0.50 Moderate 0.57 Moderate
HR Boost Volume contour agreement was suboptimal• More clarification of this boost target volume is needed• Basis of the current project
Variability of RPS target volume contour delineation among Sarcoma Radiation Oncologists has recently been assessed**
**ASTRO, San Francisco, 2014
Purpose
• To evaluate the variability in HR GTV Boost target volume delineation among sarcoma radiation and surgical oncology teams
Methods
• Radiation planning CT scans for 3 cases of RPS were distributed to 7 radiation and surgical oncology teams
• GTV (gross tumor volume) and organ contours were provided
• Teams were asked to contour HR GTV Boost volumes for each case
HR GTV Boost Contour Instructions
• Area considered to be at high risk for positive margins following resection
• Generally areas of tumor located along posterior RP musculature, ipsilateral pre-vertebral space, major vessels, or organs the surgeon would leave in situ
• Contour 1.5 cm thick
High Risk Boost Volume
GTV
Methods: Analysis of Contour Agreement
• Simultaneous truth and performance level estimation (STAPLE) algorithm*
• Kappa statistics (yield values from -1 to +1)• Kappa = -1 : complete disagreement• Kappa = +1 : complete agreement• Descriptive categories for interpretation of strength**
Kappa < 0 is poor 0.00 - 0.20 is slight 0.21 - 0.40 is fair 0.41 - 0.60 is moderate 0.61 - 0.80 is substantial 0.81 - 1.00 is almost perfect agreement
*Warfield, IEEE Transactions on Medical Imaging 2004;23:903** Landis, Biometrics 1977;33:159
Results
• Each case was contoured by 7 radiation and surgical oncology teams
• First case: RPS 1– De-differentiated (DD) liposarcoma (LPS) of right
upper quadrant
• Second case: RPS 2– Leiomyosarcoma (LMS) of left upper quadrant
• Third case: RPS 3– DD LPS of left lower quadrant with extension
through inguinal canal into upper scrotum
Results HR GTV Boost Volume Contour Agreement
Kappa AgreementRPS 1: DD LPS right upper quadrant 0.66 Moderate
RPS 2: LMS left upper quadrant 0.61 Moderate
RPS 3: DD LPS left lower quadrant 0.52 Moderate
Slightly better agreement than prior consensus project (0.50, 0.57)
Contour agreement for all cases was only moderate
HR GTV: Very Good Agreement
RPS 2: LUQ LMS
Very good contour agreement laterally along chest wall and medially along ipsilat para-vertebral space and aorta
Red: GTVOther colors: HR GTV volumes
HR GTV: Marginal Agreement
Red: GTVOther colors: HR GTV volumes
RPS 3: LLQ DD LPS
Marginal contour agreement medially along bladder and anteriorly along anterior abdominal wall
HR GTV: Marginal Agreement
Red: GTVOther colors: HR GTV volumes
RPS 1:RUQ DD LPS
Marginal agreement along liver
• 4 contours include entire liver surface in contact with tumor,
• 3 contours exclude liver
Conclusion
• Overall agreement for HR GTV boost volumes was moderate
• Contour agreement was best:– Postero-laterally, abutting chest wall– Medially, abutting RP musculature, ipsilateral para-vertebral
space, great vessels
• Contour agreement most variable:– Abutting organs such as liver and bladder– Discrepancies are explained by differing surgical opinions
regarding partial organ resections for these cases– Highlights extreme importance of collaboration between
radiation and surgical oncologist for each patient
Future Directions
• Further discussion among sarcoma radiation and surgical oncologists is needed to reach improved consensus
• An atlas with detailed examples of HR GTV volumes may be an effective educational tool