Three dimensional conformal radiotherapy treatment planning for non-small cell lung cancer.

The purpose was to determine whether new technological developments could improve radical radiotherapy for NSCLC. Patients treated with CHARTWEL to 60Gy were investigated. 3D Conformai Radiotherapy Treatment Planning 2D and 3D planning were compared in 24 patients. Dose volume histograms were constructed for planning target volumes (PTV), lung and spinal cord. 3D planning achieved a higher dose to the PTV due to a significant dosimetric advantage. Geometric coverage with 2D was adequate at the expense of higher doses to lung and spinal cord. External Immobilisation Frame An external metal immobilisation frame was validated with CT scanning. Alignment of internal and external anatomy occurred in all patients with the frame. Active Breathing Control (ABC) Intraand inter-fraction variation with ABC and effect of ABC were assessed with CT scanning and the 3D radiotherapy treatment planning software. PTVs, doses to lung, spinal cord and oesophagus were compared for free breathing and ABC in 10 patients. ABC enabled better delineation of disease and normal structures and allowed reproducible breath holds over several weeks. Reduction in V20 occurred in all plans and maximum spinal cord dose in 80 %. The reductions would give an extra margin of safety or could allow dose escalation. Assessment of Lung and Oesophageal Morbidity Acute and late lung (14 patients) and oesophageal (21 patients) morbidity were assessed. Although most developed radiological pneumonitis and spirometry generally decreased after treatment, dyspnoea did not necessarily develop. There was correlation between mean lung dose (MLD) and V20 and between PTV and the following: radiological pneumonitis score, MLD, V20. Acute dysphagia occurred in most patients with full recovery by week 8. Maximum dysphagia score correlated with maximum dose to oesophagus but not length of oesophagus treated. The results indicate that the dose limitations currently employed in the radiotherapy planning are safe and possibly conservative. CONTENTS TITLE 1 ABSTRACT 2 CONTENTS 4 LIST OF FIGURES 9 LIST OF TABLES 13 DEDICATION 15 ACKNOWLEDGEMENTS 16 SUMMARY OF ACHIEVEMENTS AND PUBLICATIONS 18 STATEMENT OF ORIGINALITY 24 ETHICAL STATEMENT 25 INTRODUCTION: THE NATURAL HISTORY AND TREATMENT OF NON-SMALL CELL LUNG CANCER 1.1 Natural history of Non-Small Cell Lung Cancer 26 Aetiology 26 Pathology 27 1.2 Surgery 30 Neo-adjuvant and Adjuvant Radiotherapy 32 Neo-adjuvant and Adjuvant Chemotherapy 34 1.3 Radiotherapy 35 CHART 35 CHARTWEL 37 Chemotherapy 38 Neo-adjuvant chemotherapy 38 Concurrent chemotherapy and radiotherapy 40 Sequential versus concurrent chemo-radiotherapy 40 Neo-adjuvant chemotherapy followed by concurrent chemo-radiotherapy 44 Adjuvant chemotherapy 44 1.4 Three-dimensional conformai radiotherapy (3D CRT) to treat non-small cell lung cancer 45 1.5 3D CRT procedures 47 Data acquisition: Tumour and patient data for planning 47 Imaging 47 Target volume and normal tissue definition 49 Definition of the GTV 49 Normal tissue constraints 52 Spinal cord tolerance 52 Oesophageal tolerance 53 Lung tolerance 54 Definition of the CTV 55 Definition of the PTV 55 PTV coverage 58 Conformai block/MLC penumbra 58 PTV to TV margins 58 Dose calculations 59 Evaluation of 3D plans 59 Verification of 3D treatment plans 62 Quality Assurance 62 1.6 Techniques to improve set-up and organ motion errors 63 Immobilisation 63 Organ motion 63 2. METHODS 2.1 Patient eligibility 66 2.2 Pre-treatment investigations 67 2.3 Treatment with chemotherapy before radiotherapy 67 2.4 Positioning of the patient 68 Immobilisation frame 68 2.5 Assessment of the immobilisation frame 70 2.6 Planning software 71 Multidata DSS® 2D planning system 71 3D Pinnacle® version 4.2f planning system 72 2.7 CT scanning for 2D/3D comparison 75 2.8 2D planning 76 2.9 3D planning 76 Prescribed dose and dose limits 79 2.10 Radiotherapy 2D/3D planning comparison 79 2.11 ABC procedure and CT scanning 82 2.12 3D planning for the FB and ABC comparison 85 2.13 Morbidity assessment 86 2.14 Statistical analysis 87 3. COMPARISON OF 2 DIMENSIONAL AND 3 DIMENSIONAL RADIOTHERAPY TREATMENT PLANNING IN LOCALLY ADVANCED NON-SMALL CELL LUNG CANCER TREATED WITH RADICAL RADIOTHERAPY 3.