RTOG Extremity Soft
Tissue Sarcoma Atlas
RTOG Sarcoma Working Group Consensus
on The GTV and CTV For Preoperative
Radiotherapy of Large High Grade Extremity
Soft Tissue Sarcoma
Dian Wang, MD., Ph.D.
Medical College of Wisconsin
11
Definition of GTV and CTV
•
Gross Target Volume (GTV): Gross tumor defined by MRI T1 plus
contrast images (MRI with contrast is required). Fusion of MRI and CT
is recommended to delineate the GTV for radiotherapy planning.
Intravenous contrast is recommended, particularly for upper extremity
lesions, where there is a greater rotational mobility and positioning
fidelity between the diagnostic MRI and the planning CT may be more
difficult to achieve
•
Clinical Target Volume (CTV) for intermediate-to-high grade
sarcoma ≥ 5 cm: Include gross tumor and clinical microscopic
margins. Typically CTV = GTV plus 3 cm margins in the longitudinal
(proximal and distal) directions. If this causes the field to extend beyond
the compartment, the field can be shortened to include the end of a
compartment. The radial margin from the lesion should be 1.5 cm
including any portion of the tumor not confined by an intact fascial
barrier, bone or skin surface. The suspicious edema defined on MRI
T2 images is often included within the above margins. However, clinical
judgment is required to make sure if the above margins need to be
extended to cover the T2 edema defined on MRI T2 images. For
example, the extensive T2 edema may be excluded if clinical judgment
suggests that the risk of the edema harboring sarcoma many cm
beyond the GTV is low or if extending the radiation field to include all of
the edema would cause excessive toxicity.
22
Example Case
• 55-year-old male with a large high-grade
round cell liposarcoma in right distal thigh.
Clinical stage (AJCC 7th edition) III
T2bN0M0G3.
– The MRI of right distal thigh showed a large well
circumscribed heterogeneous, multiloculated
mass located within the posterior thigh.
– The tumor measured 14.8 cm in craniocaudal
dimension, 7.8 cm in AP dimension, and 11.3 cm
in maximal medial-lateral dimension.
• Simulation CT images were fused with those
from the diagnostic thigh MRI
33
Consensus Contours
• The consensus contours for the GTV and
CTV were generated based on the
modification of the 95% agreement contours
by RTOG Sarcoma Working Group Radiation
Oncologists
– Dian Wang, Walter Bosch, David Roberge, Steven E.
Finkelstein, Ivy Petersen, Michael Haddock, Yen-Lin E.
Chen, Naoyuki G. Saito, David G. Kirsch, Ying J. Hitchcock,
Aaron H. Wolfson, Thomas F. DeLaney. RTOG Sarcoma
Radiation Oncologists Reach Consensus on Gross Tumor
Volume (GTV) and Clinical Target Volume (CTV) on
Computed Tomographic Images for Preoperative
Radiotherapy of Primary Soft Tissue Sarcoma of Extremity in
RTOG Studies. IJROBP June 2011
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←CTV
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←CTV
77
←CTV
88
←CTV
99
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