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CTOS, Boca Raton, 2005 A Radiation Treatment Planning Comparison for Lower Extremity Soft Tissue Sarcoma: Can the Future Surgical Wound Be Spared? Anthony.

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Presentation on theme: "CTOS, Boca Raton, 2005 A Radiation Treatment Planning Comparison for Lower Extremity Soft Tissue Sarcoma: Can the Future Surgical Wound Be Spared? Anthony."— Presentation transcript:

1 CTOS, Boca Raton, 2005 A Radiation Treatment Planning Comparison for Lower Extremity Soft Tissue Sarcoma: Can the Future Surgical Wound Be Spared? Anthony M. Griffin, BSc Colleen I. Euler, MRT(T)(M.R.) Michael B. Sharpe, PhD Peter C. Ferguson, MD, FRCSC Jay S. Wunder, MD, FRCSC Robert S. Bell, MD, FRCSC Peter Chung, MD, FRCPC Charles N. Catton, MD, FRCPC Brian O’Sullivan, MD, FRCPC Princess Margaret Hospital

2 CTOS, Boca Raton, 2005 Introduction Extremity STS: Rare, 80% lower extremity Limb salvage surgery ± radiation Usually external beam Timing: Preop vs postop

3 CTOS, Boca Raton, 2005 Introduction Why does it matter? SR2 RCT of preop rads vs postop 1 43% wound healing comps with preop vs 21% postop in lower extremity But lower dose, smaller volume 1 O’Sullivan, Lancet 2002; 359:2235

4 CTOS, Boca Raton, 2005 Introduction Decreased late tissue morbidity (fibrosis 1, fracture 2 ) Improved function Can we decrease risk of acute wound healing comps to that seen with postop rads? Normal tissue sparing possibilities with IMRT 1 Davis, Radiother Oncol, 75:48, Holt, JBJS(Am) 87:315, 2005

5 CTOS, Boca Raton, 2005 Purpose To define the future surgical wound as an organ at risk (OAR) and determine if IMRT can decrease dose to the putative surgical flaps From Malawar & Sugarbaker

6 CTOS, Boca Raton, 2005 Methods Retrospective review Lower extremity STS, deep to fascia, no ‘unplanned excision’, preop rads, digital cross- sectional imaging available, original Tx plans available, planned with CT-simulation : 174 potential cases, 24 met all criteria Planning comparison of original treatment plans (parallel-opposed pair), conformal & IMRT

7 CTOS, Boca Raton, 2005 Methods GTV from original ‘conventional’ plan formed basis of all 3 plan types CTV appropriate to management of extremity STS contoured around GTV- same for all 3 plans Surgical flaps contoured onto image set & QA’d by treating surgeon Planning parameters for conventional plans faithful to original Conformal dose distribution clinically acceptable to target and avoidance structures

8 CTOS, Boca Raton, 2005 Methods Prescribed dose to CTV 50 Gy Biopsy site treated to full dose (1.5 cm margin) Dose constraints: 30 Gy flaps, 40 Gy bone CTV/ flap overlap, CTV took priority Plan acceptable if 95% or more of the CTV covered by 95% or more of the prescribed dose

9 CTOS, Boca Raton, 2005 Methods: Plan Comparison Metrics Mean % flap treated to ≥30 Gy Mean % bone treated to ≥40 Gy Mean dose to flaps & bone Target Coverage: –Target volume receiving at least the desired dose/ total target volume Conformality Index: –Total volume receiving at least the desired dose/ target volume receiving at least the desired dose

10 CTOS, Boca Raton, 2005 Results 24 patients Mean tumor size 10.9 cm (5-19 cm) Mean flap volume: cm 3 ( cm 3 ) Mean bone volume in field: cm 3 ( cm 3 ) Lateral flap Medial flap Biopsy site GTV CTV Tibia Fibula

11 CTOS, Boca Raton, 2005 Plan Comparisons

12 CTOS, Boca Raton, 2005 Wilcoxon Signed Rank test of differences in the means for each of the 3 plan pairs Original: Conformal Original: IMRTConformal: IMRT Mean dose to flap (Gy) p= 0.018p= Mean percentage flap treated to ≥ 30 Gy p= 0.391p=

13 CTOS, Boca Raton, Plan Types- Flaps & CTV Coverage

14 CTOS, Boca Raton, Plan Types- Bone & CTV Coverage

15 CTOS, Boca Raton, 2005 Discussion IMRT lowers dose to future flaps & spares greater percentage of flap volume No compromise in tumor (target) coverage Bone sparing significant as well

16 CTOS, Boca Raton, 2005 Discussion Requires  multidisciplinary collaboration (surgeon & radiation oncologist) Transfer of putative flaps from patient to planning CT and back to patient PTV: margins dependent on minimizing set up error (immobilization devices, daily cone beam CT verification, adaptive RT)

17 CTOS, Boca Raton, 2005 Discussion Fine in theory- does it work? Phase II preop IMRT study commenced July 2005 Acute wound healing comps. primary endpoint 59 patients total- 8 so far

18 CTOS, Boca Raton, 2005 Thank You


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