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Image-Guided Adaptive Therapy for the
Treatment of Lung Cancer
C Ramsey, S Mahan, D Chase
Thompson Cancer Survival Center, Knoxville,TN
Adaptive IGRT for Lung
• The first Lung Cancer
patient was treated with
Helical Tomotherapy at the
Thompson Cancer Center
in July 2003
• 7 lung cancer patients have
been treated for a total of
199 fractions
• Each patient had CT
imaging prior to treatment
delivery
Lung Window
Bone Window
TCSC-RT 0301: Lung Tomo Protocol
Prescription
• Initial: 44 Gy (2.0 Gy/fraction)
• Boost: 20 Gy (2.5 Gy/fraction)
Margins
• Initial: GTV + 2-cm
• Boost: GTV + 1-cm (with DIBH)
Plan Optimization Parameters:
• Pitch: 0.333
• Thickness: 2.5
• Modulation: 2.5
The total lung volume (right and
left lung minus the gross tumor
volume) receiving greater than
20 Gy must be 35% or less
Lung Adaptive Therapy
TomoImage Fraction #1
30
Volume (cc)
25
Patient #1
Patient #2
Patient #3
20
15
10
GTV
5
0
0
10
20
30 40 50
Elapsed Days
60
70
Tumor Response
• During the course of the therapy (with or
without concurrent chemotherapy), the
GTV can reduce in volume by a factor of 3
• As the GTV shrinks, the target is
effectively being treated with an increasing
margin
TomoImage Fraction #30
GTV
Lung Adaptive Therapy
• The PTV is reduced every five
fractions based on GTV volume
reduction in the previous five
TomoImages
• The GTV is reduced in the
planning CT image to match
each weeks measured tumor
volume
• The GTV is still expanded into
the PTV (i.e. margins are the
same)
• Adaptive
therapy’s
impact
increases the larger the original
GTV volume and the greater the
Original Treatment Plan
Adaptive Composite Plan
Lung Adaptive Therapy
PTV
Ips. Lung
Volume (cc)
30
25
Patient #1
Patient #2
Patient #3
20
15
10
5
0
0
10
20
30 40 50
Elapsed Days
60
70
Lung mass reduced to 36%
of the original tumor volume
Non-Adaptive
Weekly Adaptive
Lung Adaptive Therapy
PTV
Volume (cc)
30
25
Patient #1
Patient #2
Patient #3
20
15
10
5
0
0
10
20
30 40 50
Elapsed Days
Ips. Lung
Non-Adaptive
60
70
Lung mass reduced to 25%
of the original tumor volume
Weekly Adaptive
Lung Adaptive Therapy
Volume (cc)
30
25
PTV
Patient #1
Patient #2
Patient #3
20
15
10
5
0
0
10
20
30 40 50
Elapsed Days
Lung mass reduced to 81%
of the original tumor volume
Weekly Adaptive
60
70
Ips.
Lung
Non-Adaptive
Adaptive IGRT for Lung
Based on the results of this feasibility study, adaptive
therapy at a minimum has the potential to decrease
radiation induced damage to healthy lung tissue
• The level of improvement increases with larger initial CTV’s
and with increased volume reduction during treatment
The potential pitfall of this type of adaptive therapy is the
potential for underdosing microscopic extension
• As the visible GTV decreases, the assumption is that the
microscopic extension is also shrinking at the same rate
• However, margin is still added around the GTV in adaptive
therapy, and the final PTV is typically the same size or larger
than the initial CTV