3 ObjectivesDescribe the role of 4-dimension (4-D) CT scanning in radiation lung treatment planning.Describe the two techniques of stereotactic body radiation therapy: Non-coplanar Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy.Compare the expected local control rates for early stage lung cancer with SBRT and surgery.
5 What is Radiation Therapy? Using ionizing radiation to achieve lethal damage to target tissuesThe radiation causes lethal breaks in the cells DNA
6 Linear Accelerator (LINAC) Delivers high energy X-Rays (photons) or electrons to the patient’s tumorOur treatment plans try to maximize dose to the tumor while minimizing dose to normal tissueModern techniques include IMRT, IGRT, SRS, SBRT
7 How does a LINAC WorkMicrowaves accelerate electrons to extremely high speeds and slam them into a metal targetHigh energy x-rays are produced by this collisionThe x-rays are shaped using several methods as they exit the machine to conform to the target
8 Why do we need SBRT? LC with SBRT is 92-97% Radiation Modality 5-year Overall SurvivalConventional RT20%SBRT42%Radiother Oncol 2010
9 Problem Lung tumors move a lot with respiration ≈40% lung tumors move >0.5cm≈10-15% lung tumors move >1.0cmHow can we target a lung tumor more accurately with tight margins to minimize toxicity to normal lung?
11 4-D CT ScanAdvances in technology have made CT scanning much faster and accurateTraditional CT scan only images the tumor at one point of the breathing cycleMany 3-D CT sets are obtained corresponding to a particular breathing phase
13 4-D CT ScanOver-sampling images at every position of interest along the patients axisImages are tagged with breathing signalsImages are sorted retrospectively based on corresponding breathing signal
14 MIP (Maximum Intensity Projection) MIP reduces the multiple 3-D CT images from a 4-D data set into a single 3-D data setMIP represents the maximum intensity encountered by the corresponding voxels in all the individual 3-D phase image sets of the 4-D image set.
18 Cone Beam CTAcquires real-time 3D images of the patient while on the treatment table with a single rotation of the gantryPatient can be adjusted immediately to align tumor targetResponse of tumor to treatment can be monitored
21 Optimal Radiation Treatment Encompass the tumor with a very conformal dose cloud with rapid dose fall-off outside your targetMinimize tumor motion to allow smaller treatment field, thus minimizing dose to normal tissueVerify patient positioning with immediate imaging
22 Modern Techniques IMRT-Intensity Modulated Radiation Therapy VMAT-Volumetric Arc TherapyIGRT-Image Guided Radiation TherapySBRT-Stereotactic Body Radio-Therapy
23 SBRTAdvances in hardware (imaging), software innovation (computational algorithms), and faster computer processors have enable development of SBRT techniques.SBRT involves highly precise, high dose, short course treatments (3-5 fractions)SBRT allows precise targeting and techniques to minimize tumor motion
27 RapidArcVMAT (Volumetric Modulated Arc Therapy) is a new radiation technique using sophisticated treatment plan to deliver a continuous beam (arc) of radiation as the linear accelerator rotates around patient
28 RapidArcPlanning optimization algorithm that simultaneously changes 3 parameters during treatmentShape of treatment aperturedelivered dose intensitySpeed of gantry rotationTreatment time is very rapid
35 Patient E.M.73 y/o M with hx of LUL NSCLC s/p resection in 2011 with new RUL 2cm nodule in Jan 2013 (PET hot 5.3 SUV)Biopsy caused penumothorax and path showed atypical cellsPlan: 5000 cGy in 5 fractions (1000 cGy per fraction)
37 SBRT ResultsPhase 2 multicenter study of 59 pts with T1 or T2 inoperable early stage tumors (medical condition precluded resection)3 SBRT treatments (18Gyx3=54 Gy)Local control 97%Local/Regional Control 87%3-year OS 56%Median OS 48 monthsTimmerman et al., JAMA 2010
38 SummaryAdvanced Imaging has revolutionized targeting in Radiation OncologyModern radiation techniques have enabled dose escalation and excellent local controlSBRT is an excellent option for patients who are not surgical candidates or refuse surgery