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Technical Advances in radiotherapy for Lung (and liver) Cancer


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Technical Advances in radiotherapy for Lung (and liver) Cancer. Dr. Peter Balter

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Technical Advances in radiotherapy for Lung (and liver) Cancer

  1. 1. Technical Advances in Radiotherapy for Lung (and Liver) Cancer Peter Balter, Ph.D.
  2. 2. Disclosure • Dr. Balter is PI on a sponsored research agreement with Philips Medical Systems. • Dr. Balter is co-PI on a sponsored research agreement with Varian Medical Systems (who is sponsoring my presence in Thailand for the SBRT conference)
  3. 3. Technologies for improvement in XRT of the thorax in the last 10 years • 4DCT/Respiratory correlated imaging • Motion management during treatment • Intensity Modulated Radiation Therapy • Image Guided Radiation Therapy (IGRT) • Protons
  4. 4. 4DCT/Respiratory correlated imaging • Allows determination of the position of tumor over the entire respiratory cycle with respect to – Critical structures – Boney Anatomy • Allows the design of a treatment plan – Resilient to respiratory motion – Timed with respiratory motion (gating) • Demonstrates the need to mitigate motion – Breath-hold – Abdominal compression
  5. 5. General approach to 4-D image acquisition • Acquire image data continuously during respiration • Reconstruct the image data at specific phases in the respiratory cycle for each patient location. • Combine image data at same phase from several respiratory cycles. • Result: A series of 3-D CT scans each representing a different phase in the respiratory cycle.
  6. 6. Standard Treatment Internal Target Volume (ITV) approach: • Treat track of tumor motion • Based on a 4-D dataset • Custom margins for each tumor ITV Motion management during treatment
  7. 7. Gating • Dynamic: Deliver dose when tumor is within the beam portal • Breath-hold: Ask or force the patient to hold their breath at a given level then deliver the beam  Generally done with visual feedback Motion management during treatment
  8. 8. 4DCT of moving SBRT target Same patient residual motion during breath-hold Example: Lung SBRT case that required respiratory motion management
  9. 9. Intensity Modulated Radiation Therapy (IMRT)/ Volumetric Modulated Arc Therapy (VMAT) • A computer optimizer with a skilled operator designs a plan based on clinical requirements (inverse planning) – create highly conformal dose distributions – simultaneously treat to several dose levels – compensate for non-uniform scatter at the lung tumor interfaces – To quantify and control normal tissue dose
  10. 10. IMRT/VMAT learning curve • Observations and prospective : – MDACC: IMRT plan quality in 10 years ago is significantly different from the plan quality now with the same planning and delivery systems. – Publications: • An external audit of IMRT plan showed that an experienced center can yield superior IMRT plans • Doismetrists with higher level of IMRT experience produced a better quality head and Neck IMRT plan.
  11. 11. Automated IMRT Optimization Tools • Auto-plan Systems (In-house and commercial) – Improves consistency and overall quality of plans • Multicriteria Optimization (commercial) – Provides real-time feedback of plan objective trade-offs • These tools allow all centers to achieve high quality IMRT
  12. 12. Image Guided Radiotherapy (IGRT) • High quality/low dose imaging has become a standard feature of our linear accelerators • Enables: – Reduced margins – Gating with verification – Hypo-fractionation (SBRT) – Adaptive planning • Adapt to changing anatomy
  13. 13. IGRT based targeting in the Thorax • Projection Imaging • Allows setup to boney anatomy • Allows setup to implanted markers • Has been show to greatly reduce systematic setup errors • Volumetric Imaging • Allows direct setup to soft tissue lesions • Allows evaluation of anatomical changes
  14. 14. Adaptive Planning-Thorax • Many tumors/patients change size and shape during the course of radiotherapy • Normal anatomy/breathing pattern can change more • If we do not adapt to these changes – We may miss tumor – We may overdose normal anatomy – We may miss an opportunity to dose escalate • Thorax – big cavity where tumor, fluid and air can all change places with no external indication – Often the goal of radiotherapy is to open airways which then cause changes in internal anatomy
  15. 15. 10/11/2010 – 0 days treatment-4 days after sim Simulation CT Daily CBCT Daily CBCT Daily CBCT On-treatment soft tissue imaging demonstration of the need for adaptive planning due to changes in breathing pattern.
  16. 16. • The physics of protons may enable better sparing of normal tissues than the best IMRT/VMAT. Protons: Better treatment through physics Gillin
  17. 17. -20.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Protons: Better treatment through physics Protons (120 MeV 4cm SOBP) Electrons (20 MeV) Photons(6 MV) RelativeDose Depth in Water (cm) In contrast to Electrons and Photons there is nearly perfect fall off at the end of the proton range Gillin
  18. 18. Example thorax case: Protons have a limited range, which should limit toxicity (no low dose bath) Patient with T2, N0, MX COPD 87.5 CGE Limited dose to the non- involved lung Note: Penetration through lung 3 fields, Lateral and 2 Posterior obliques Standard fractionation Gillin
  19. 19. Protons: Opportunities • The same physics that helps protons better spare tissues makes them much more sensitive to uncertainness – Scattered protons have poor proximal coverage, sine the beam is designed for distal edge – Respiratory motion – Anatomical changes • Protons technologies are still evolving quickly to mitigate these issue – Intensity modulated proton therapy – Robust optimization Dong
  20. 20. Thank you for your attention Acknowledgments • Zhongxing Liao, M.D. • Joe Chang, M.D., Ph.D. • James Cox, M.D. • Ritsuko Komaki, M.D. • many others • Lei Dong, Ph.D. • Radhe Mohan, Ph.D. • Michael Gillin, Ph.D. • George Starkschall, Ph.D.