Quantitative Dosimetric Analysis Of Patterns Of Local Relapse After IMRT For Primary Extremity Soft Tissue Sarcomas Ryan M. Lanning, Sean L. Berry, Michael R. Folkert, and Kaled M. Alektiar Dept. of Radiation Oncology and Medical Physics Memorial Sloan-Kettering Cancer Center
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Quantitative Dosimetric Analysis Of Patterns Of Local Relapse After IMRT For Primary Extremity Soft Tissue Sarcomas Ryan M. Lanning, Sean L. Berry, Michael.
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Quantitative Dosimetric Analysis Of Patterns Of Local Relapse After IMRT For Primary Extremity Soft Tissue Sarcomas
Ryan M. Lanning, Sean L. Berry, Michael R. Folkert, and Kaled M. Alektiar
Dept. of Radiation Oncology and Medical PhysicsMemorial Sloan-Kettering Cancer Center
Disclosures
• We have no conflicts of interest to disclose.
Characterizing Local Recurrence
Marginal
Central
Distant
Scar
RT Field
Objectives
• Characterize local recurrence of extremity STS treated with adjuvant IMRT based on dose received to the recurrence volume.
• Determine any patient, tumor, or treatment characteristics that may predict local recurrence.
Soft Tissue Sarcoma Study Population
Time Period: 2/2002 – 12/2010# of patients: 165Male: 101 (61%)Female: 64 (39%)Median Age: 55 (19-88) years
Pre-op IMRT:34 (21%)Median: 50Gy (48-50)
Post-op IMRT:131 (79%)Median: 63Gy (27-66.6)
Tumor and Treatment Characteristics
% nTumor Size: >10 cm 44% 73Grade: High 87% 143Depth: Deep 91% 150Site: Lower extremity 74% 123Margin Status: Positive / Close 52% 85Adjuvant Chemo: Yes 27% 45
Original RT Fields and LR Patterns
Recurrence Based on Dose Distribution
Recurrence
CTVPTV
Dosimetric Characterization of Recurrence
0 20 40 60 80 100 1200
10
20
30
40
50
60
70
80
90
100
110
Marginal Central
Dose (% Prescription)
Volu
me
(%)
V95
Relationship to 95% IDL*
Central =Completely
within
Marginal =Crosses
Distant =Completely
outside
* : Milano MT et al. IJROBP 2010
Outcomes
n % 5-yr LR Median time to LR (mo)
Overall 13 -8.4%
(95% CI: 3.8 - 13)19
(range: 9 - 61)
Central 4 312.9%
(95% CI: 0 - 5.7)24
(range: 13 - 28)
Marginal 8 615.0%
(95% CI: 1.4 - 8.6)18
(range: 9 - 61)
Distant 1 8 0.7%(95% CI: 0 – 2.1)
19
Median Follow-up = 42 months
Predictors of Local RecurrenceFactor Events 5-yr LR (%) P-value
S = Surgery C = Chemotherapy R = EBRT B = Brachytherapy
CTV: GTV + 1-1.5 cm in radial axis
PTV: CTV plus 1 cm margin in all directions
Volume Expansion: Pre-op IMRTCT
V: G
TV +
4 c
m in
long
axi
s
CTV
: Tum
or b
ed +
4 c
m in
long
axi
s
PTV: CTV plus 1 cm margin in all directions
CTV: Tumor bed + 1-1.5 cm in radial axis
Volume Expansion: Postop IMRT
Local Recurrence: EBRT vs IMRT
• Competing risks, cumulative incidence, Gray’s test and Fine and Gray regression were used to estimate 5-y local recurrence:
– IMRT:7.6% (95% CI 3.4-11.8%)
– Conventional EBRT: 15% (95% CI 9.2-20.9%)
P = 0.049
Courtesy of MR Folkert
Discussion points – Basis of Improved Outcome?
• Improved conformality and homogeneity of dose may be the basis of improved local control.
1. Swanson EL et al, Int J Radiation Oncology Biol Phys. 2012 83(5):1549-57. 2. Stewart AJ et al, Radiother Oncol. 2009 Oct;93(1):125-30.3. Griffin AM et al, Int J Radiat Oncol Biol Phys. 2007 Mar 1;67(3):847-56.
Conformity/ConformalityHomogeneity/Heterogeneity
Study IMRTConventional
EBRT IMRTConventional
EBRTSwanson et al1 0.75 0.51 0.066 0.073Stewart et al2 1.33-1.59 1.76 1.036-1.045 1.052
Griffin et al3 1.27 1.76-2.34 n/a n/a
Courtesy of MR Folkert
Predictors of Local RecurrenceFactor Events 5-yr LR (%) 95% CI P-value