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Image-Guided Adaptive Therapy for the Treatment of Lung Cancer C Ramsey, S Mahan, D Chase

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

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Image-Guided Adaptive Therapy for the Treatment of Lung Cancer C Ramsey, S Mahan, D Chase

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  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 Bone Window Lung 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. 30 25 Patient #1 Patient #2 20 Patient #3 Volume (cc) 15 10 5 0 0 10 20 30 40 50 60 70 Elapsed Days Lung Adaptive Therapy TomoImage Fraction #1 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. 30 25 Patient #1 Patient #2 20 Patient #3 Volume (cc) 15 10 5 0 0 10 20 30 40 50 60 70 Elapsed Days Lung Adaptive Therapy PTV Ips. Lung Lung mass reduced to 36% of the original tumor volume Non-Adaptive Weekly Adaptive

  7. 30 25 Patient #1 Patient #2 20 Patient #3 Volume (cc) 15 10 5 0 0 10 20 30 40 50 60 70 Elapsed Days Lung Adaptive Therapy PTV Lung mass reduced to 25% of the original tumor volume Ips. Lung Non-Adaptive Weekly Adaptive

  8. 30 25 Patient #1 Patient #2 20 Patient #3 Volume (cc) 15 10 5 0 0 10 20 30 40 50 60 70 Elapsed Days Lung Adaptive Therapy 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

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