Variation in size and position of the planning target volume in the transverse plane owing to respiratory movement during radiotherapy to the lung.

Movement of thoracic tumours with respiration poses a real dilemma in terms of the accuracy of delivering radical radiotherapy in patients with carcinoma of the lung. Movements in the craniocaudal direction have previously been described. This technical note describes ten patients planned for radical lung radiotherapy using CT. The study assesses the maximum impact of respiration on the planning target volume in the transverse plane by comparing the planning CT appearances during quiet respiration with those during full inspiration and full expiration. The study demonstrated the potential impact of respiratory movement on the planning target volume and, hence, implications for local tumour control.