Page 1. Helical (Spiral) Tomotherapy. UW Helical Tomotherapy Unit. Helical (Spiral) Tomotherapy. MVCT of an Anesthetized Dog with a Sinus Tumor

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1 Helical (Spiral) Tomotherapy Novel Clinical Applications of IMRT Linac Ring Gantry CT Detector X-Ray Fan Beam Binary Multileaf Collimator Binary MLC Leaves James S Welsh, MS, MD Department of Human Oncology University of Wisconsin, Madison CT Couch Helical Fan Beam Helical Scanning Helical (Spiral) Tomotherapy UW Helical Tomotherapy Unit X-Ray Beam Helical Fan Beam Delivery Binary MLC Leaves Status June 2003 MVCT scans obtained on 10 lung and 10 prostate cancer patients 9 dogs treated 10 human patients treated 9 palliative 1 definitive Advantages of Helical Tomotherapy MVCT of an Anesthetized Dog with a Sinus Tumor CT component allows real-time imaging of patients to verify set-up and detect variations in positioning Relative Simplicity An optimal means of delivering co-planar therapy Adaptive Radiotherapy Conformal Avoidance Wide range of IMRT applications Sinus Tumor Eroded Bone Page 1

2 MVCT Before Our First Patient Treatment MVCT of a Lung Cancer Patient #1 at 3 cgy Soft Tissue Window Lung Window Target Volume Lung Tumor MVCT of a Lung Cancer Patient # 2 at 3 cgy Soft Tissue Window Lung Window MVCT of a Prostate Cancer Patient at 2.5 cgy Prostate Lung Tumor Advantages of Helical Tomotherapy CT component allows real-time imaging of patient to verify set-up and detect variations in positioning Relative Simplicity An optimal means of delivering co-planar therapy Adaptive Radiotherapy Conformal Avoidance 95% 90% 50% 20% Preliminary Tomotherapy Planning Page 2

3 95% 90% 50% 20% Preliminary Tomotherapy Planning D plans Tomotherapy Tomotherapy decreases mean NTD (spinal cord) Spinal cord NTDmean P1 P2 P3 P4 P5 Mean Patient Conformal Avoidance Wide field XRT is frequently employed to target regional micrometastatic extension This regional disease extension is not precisely defined in terms of anatomic detail As a consequence, normal critical tissues are frequently irradiated and yield toxicities Conformal avoidance can shield these structures and improve the therapeutic index by decreasing these often permanent and debilitating NTCPs Salivary glands: Xerostomia/Dental hygiene/osteonecrosis Oto-acoustic apparatus: Hearing/Balance Optic/Lacrimal tissues: Vision/Xerophthalmia/Corneal complications Rationale for Conformal Avoidance Radiotherapy The gross tumor volume (GTV) may not be clearly visible Uncertainty in defining the clinical target volume (CTV) The planning target volume (PTV) may be uncertain The target dose is limited by normal sensitive tissue Conformal avoidance is the ideal paradigm to treat suspected regional/nodal involvement Conformal dose-distribution with tomotherapy Continuum Between Conformal Therapy and Conformal Avoidance Know where tumor is and will not harm sensitive tissue Don t really know where tumor is May miss part of target if overly conformal..and still harm sensitive tissue Page 3

4 The Mantle Successfully used for many decades A classic example of the need to treat invisible microscopic regional disease Generally not easy to duplicate using conformal therapy A potential application of conformal avoidance IMRT Can reduce dose to Thyroid, Larynx, Heart, Spinal cord thereby reducing complications Can reduce dose to breast in young women (possibly) reducing risk of future breast cancer Conformal Mantle Field Conformal Avoidance Radiotherapy for A Mantle Equivalent using Helical Tomotherapy Lungs Regional field Mediastinal L.axila node Spine Larynx R.axila node Subtotal/Total Lymphoid Irradiation The dose should be Divided by 10 Inverted-Y Can be effectively duplicated using IMRT via linac or helical tomotherapy Significantly less dose to sensitive normal structures than older techniques is possible Page 4

5 Mesothelioma ROI slice 27 Dose Rate Cumulative Dose Tomotherapy Slice 27 Mesothelioma Slice Dose 31 DistributionsSlice % 50 % 50 % 80 % 80 % 80 % 90 % 90 % 90 % Partial Breast Irradiation Good clinical results have been obtained using HDR brachytherapy Recent applications of partial breast irradiation using external beam approaches Visualization of target and immobilization of breast will be essential for success of this approach Limited Field Prone Breast Limited Field Prone Breast Muscle Skin PTV GTV Lt Lung Rt Lung Page 5

6 IMRT for complicated tumor volumes IMRT can handle complicated tumor volumes using either a conformal therapy or conformal avoidance approach High conformality of isodose curves Lower doses to surrounding normal structures Higher dose to tumor volume Skull Irradiation Rt Optic Nerve PTV Rt Eye Lt Eye Chiasm Lumbar Spine Treatment MVCT, Simple Contour, Plan & Treat Palliative Case: 30 Minutes Total Setup ~3min MVCT ~7min Contour ~10min Kidneys PTV Optimize ~5min Simple Contour Delivery ~5min Page 6

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8 Summary Conformal avoidance radiotherapy, the complement to conformal radiotherapy, focuses on avoiding dose to normal tissue IMRT, especially helical tomotherapy appears particularly well-suited for conformal avoidance Many innovative clinical procedures will evolve from conformal avoidance IMRT Potential Clinical Applications of Conformal Avoidance IMRT Improved irradiation of nodal chains using the conformal avoidance strategy Improved Mantle and Inverted-Y Para-aortic irradiation for GYN, GU and lymphoid malignancies Brain-sparing total scalp irradiation Scalp-sparing whole brain irradiation Pacemaker/defibrillator avoidance Bone marrow ablation while sparing visceral organs Craniospinal Irradiation Potential Clinical Applications of Conformal Avoidance IMRT Accelerated partial breast irradiation Complicated tumor volumes mesothelioma Extracranial stereotactic radiotherapy Widespread metastatic disease? Visible disease handled with radiotherapy Microscopic disease handled by chemotherapy Intermediate disease identified by PET and handled by IMRT Page 8