1. Image-Guided Adaptive Therapy for the Treatment of Lung Cancer
C Ramsey, S Mahan, D Chase
Thompson Cancer Survival Center, Knoxville,TN

2. 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

3. 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

4. Lung Adaptive Therapy Tumor Response
TomoImage Fraction #1 5 10 15 20 25 30 40 50 60 70
Elapsed Days
Volume (cc)
Patient #1
Patient #2
Patient #3
GTV
TomoImage Fraction #30
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
GTV

5. Lung Adaptive Therapy
Original Treatment Plan
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 tumor response
Adaptive Composite Plan

6. Lung Adaptive Therapy PTV Ips. Lung5 10 15 20 25 30 40 50 60 70
Elapsed Days
Volume (cc)
Patient #1
Patient #2
Patient #3
Ips. Lung
Lung mass reduced to 36% of the original tumor volume
Non-Adaptive
Weekly Adaptive

7. Lung Adaptive Therapy PTV5 10 15 20 25 30 40 50 60 70
Elapsed Days
Volume (cc)
Patient #1
Patient #2
Patient #3
Lung mass reduced to 25% of the original tumor volume
Ips. Lung
Non-Adaptive
Weekly Adaptive

8. Lung Adaptive Therapy PTV Ips. Lung5 10 15 20 25 30 40 50 60 70
Elapsed Days
Volume (cc)
Patient #1
Patient #2
Patient #3
PTV
Ips. Lung
Lung mass reduced to 81% of the original tumor volume
Weekly Adaptive
Non-Adaptive

9. 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