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