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