Radiotherapy Planning for Esophageal Cancers

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Radiotherapy Planning for Esophageal Cancers

• Parag Sanghvi, MD, MSPH
• 9/12/07
• Esophageal Cancer Tumor Board
• Part 1

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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

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Radiation for Esophageal Cancers

• Post Operative
• Rare difficult to tolerate
• 45 Gy
• Palliative
• Dysphagia
• 30 35 Gy

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Treatment Planning

• Simulation
• Immobilization
• Vac Lok
• Isocenter set-up
• 2D vs. 3D
• 3D Treatment planning CT
• Tattoos
• Daily Set-up

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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

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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

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Margins / Normal Tissue Tolerances

• Margins / PTV definitions
• Superior / Inferior GTV 5 cm
• Lateral GTV 2 cm
• Normal Tissue Tolerances Organs _at_ Risk (OAR)
• Cord - max dose 45 -50 Gy
• Lung V 20 Gy - 20 -30
• Liver V 30 Gy 23- 30
• Kidney
• Heart

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Radiation Toxicities

• Esophagitis
• Esophageal Stricture
• Radiation Pneumonitis
• V20 Gy lt 20-40 V30 Gy lt 18 Mean Lung Dose lt20
  Gy
• Post-operative Pulmonary complications
• MDACC study showed that the amount of Lung that
  is spared from 5 Gy of radiation predictive

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Radiation Toxicities

• Pericarditis
• Cardiovascular disease
• V40 Gy lt 30
• Radiation Nephropathy
• Limit dose to atleast 2/3 of 1 Kidney

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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

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Treatment Planning - Evaluation

• Dose Volume Histograms
• CT data allows to quantify dose received by tumor
  as well as organs at risk

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3D Planning
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3D Planning
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3D Planning
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3D Planning
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3D Planning
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3D Planning
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3D Planning
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3D Planning - DVH
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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

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IMRT - Benefits

• Normal Tissue sparing
• Reduced late toxicities
• Dose escalation
• Dose painting
• Ability to increase dose to areas of higher tumor
  burden
• Re-irradiation

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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

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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

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Requirements for IMRT

• LINAC
• Beam modulation device
• MLC (multi-leaf collimator)
• MlMiC (Peacock system)
• Compensators
• (Inverse) treatment planning software
• QA program