Radiotherapy Planning for Esophageal Cancers Parag Sanghvi, MD, MSPH 9/12/07 Esophageal Cancer Tumor Board Part 1

Radiation for Esophageal Cancers  Definitive  Cervical Esophagus – 60 – 66 Gy  Thoracic/GE junction – 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 – Risk (OAR) Cord - max dose Gy Lung V 20 Gy % Liver V 30 Gy – % 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 - 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