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 Conformal 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) Intra- and 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