Radiotherapy Planning for
Esophageal CancersParag Sanghvi, MD, MSPH
9/12/07Esophageal Cancer Tumor Board
Part 1
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
Radiation for Esophageal Cancers Post – Operative
Rare; difficult to tolerate 45 Gy
Palliative Dysphagia 30 – 35 Gy
Treatment Planning Simulation
Immobilization Vac Lok
Isocenter set-up 2D vs. 3D 3D – Treatment planning CT
Tattoos Daily Set-up
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
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
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
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
Radiation Toxicities Pericarditis Cardiovascular disease
V40 Gy < 30% Radiation Nephropathy
Limit dose to atleast 2/3 of 1 Kidney
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
Treatment Planning - Evaluation Dose Volume Histograms
CT data allows to quantify dose received by tumor as well as organs at risk
3D Planning
3D Planning
3D Planning
3D Planning
3D Planning
3D Planning
3D Planning
3D Planning - DVH
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
IMRT - Benefits Normal Tissue sparing
Reduced late toxicities
Dose escalation
Dose painting Ability to increase dose to areas of higher tumor burden
Re-irradiation
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
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
Requirements for IMRT LINAC
Beam modulation device MLC (multi-leaf collimator) MlMiC (Peacock system) Compensators
(Inverse) treatment planning software
QA program