Radiotherapy Planning For Esophageal Cancers

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Radiotherapy Planning For Esophageal Cancers

  1. 1. Radiotherapy Planning for Esophageal Cancers Parag Sanghvi, MD, MSPH 9/12/07 Esophageal Cancer Tumor Board Part 1
  2. 2. Radiation for Esophageal Cancers  Definitive  Cervical Esophagus – 60 – 66 Gy  Thoracic/GE junction – 50 -54 Gy  Dose escalation has not shown improved survival in definitive CRT for esophageal cancers (INT 0123)  Neoadjuvant  T3 or higher  N+  45 – 50 Gy
  3. 3. Radiation for Esophageal Cancers  Post – Operative  Rare; difficult to tolerate  45 Gy  Palliative  Dysphagia  30 – 35 Gy
  4. 4. Treatment Planning  Simulation  Immobilization  Vac Lok  Isocenter set-up  2D vs. 3D  3D – Treatment planning CT  Tattoos  Daily Set-up
  5. 5. Treatment Planning 2D Era – RTOG 8501  RTOG 8501 compared CRT (50 Gy) to RT alone (64Gy)  Mid/Lower Esophageal Cancers  Initial Field was AP/PA to 30 Gy in CMT arm  Extended from SCV region to GE junction  Omitted SCV nodes in lower esophageal tumors  Boost field was tumor + 5 cm sup/inf with a 3 field or opposed obliques  Advantages  AP/PA limited lung dose  Replacing PA with oblique fields limited spinal cord dose  Disadvantages  For distal tumors, significant cardiac volume  Entire extent of the esophagus treated
  6. 6. Treatment Planning – 3D Era  Target Delineation  PET-CT fusion  EUS findings  Definitions  GTV – Gross Tumor Volume ( Tumor + grossly enlarged LN)  CTV – Clinical Target Volume – Includes microscopic disease  PTV – Planning Target Volume – accounts for setup error and intra-fraction motion
  7. 7. Margins / Normal Tissue Tolerances  Margins / PTV definitions  Superior / Inferior – GTV + 5 cm  Lateral – GTV + 2 cm  Normal Tissue Tolerances – Organs @ Risk (OAR)  Cord - max dose 45 -50 Gy  Lung V 20 Gy - 20 -30%  Liver V 30 Gy – 23- 30%  Kidney  Heart
  8. 8. Radiation Toxicities  Esophagitis  Esophageal Stricture  Radiation Pneumonitis  V20 Gy < 20-40%; V30 Gy < 18%; Mean Lung Dose <20 Gy  Post-operative Pulmonary complications  MDACC study showed that the amount of Lung that is spared from 5 Gy of radiation predictive
  9. 9. Radiation Toxicities  Pericarditis  Cardiovascular disease  V40 Gy < 30%  Radiation Nephropathy  Limit dose to atleast 2/3 of 1 Kidney
  10. 10. Treatment Planning  3D Treatment Planning (CT- based)  Start AP/PA  Treat to cord tolerance  39.6 – 41.4 Gy  Then off-cord  2 field or 3 field  AP/RAO/LAO for cervical/upper thoracic lesions  AP/RPO/LPO for lower lesions  RAO/LPO for distal esophagus lesions  Treat to total 50.4 – 54 Gy
  11. 11. Treatment Planning - Evaluation  Dose Volume Histograms  CT data allows to quantify dose received by tumor as well as organs at risk
  12. 12. 3D Planning
  13. 13. 3D Planning
  14. 14. 3D Planning
  15. 15. 3D Planning
  16. 16. 3D Planning
  17. 17. 3D Planning
  18. 18. 3D Planning
  19. 19. 3D Planning - DVH
  20. 20. IMRT  Intensity Modulated Radiation Therapy  Clinical Rationale  Tumors arise from/within normal tissues  Normal tissues often limit the radiation doses that can be safely prescribed and delivered  Organs at risk in close proximity may have limited radiation tolerance  IMRT allows for the reduction of radiation dose delivered to normal tissue  Ability to maintain a high dose to the tumor
  21. 21. IMRT - Benefits  Normal Tissue sparing  Reduced late toxicities  Dose escalation  Dose painting  Ability to increase dose to areas of higher tumor burden  Re-irradiation
  22. 22. IMRT - Basics  Ability to break a large treatment port into multiple smaller subsets (field segments or pencil beams)  Through utilization of MLCs or other intensity modulation technology  A computer system to enable such field fragmentation  Computer system capable of performing inverse treatment planning  Defining the problem/solution upfront in numeric format
  23. 23. IMRT - Basics  Multiple static non-coplanar radiation fields  Each field has a unique radiation intensity profile  The fluency of radiation is altered during the delivery of the radiation field  Multileaf collimator  Planning CT scan (can be “fused” to an MRI or PET scan)  The tumor/volumes and critical structures are drawn  Prescription dose and dose constraints are programmed into the radiation-planning software for generation of the radiation plan
  24. 24. Requirements for IMRT  LINAC  Beam modulation device  MLC (multi-leaf collimator)  MlMiC (Peacock system)  Compensators  (Inverse) treatment planning software  QA program

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