Radiothérapie thoracique en conditions stéréotaxiques : difficultés rencontrées lors de la mise en route et solutions proposées

Abstract

The aim of this paper is to describe the difficulties encountered when implementing stereotactic radiotherapy of non-small cell lung cancer (T1-T2, N0, M0) using a voluntary breath-hold technique. From 25/03/2010 to 22/02/2011, eight patients with a non-small cell lung cancer were selected for treatment. CT images were obtained with the patient maintaining breath-hold using a spirometer. Treatment was delivered when the patient maintains this level of breath-hold. Treatment was performed with a 4MV and 10MV photon beams from a linear accelerator Varian 2100CS, equipped with a 120 leaves collimator. 60Gy or 48Gy were delivered, in four sessions, to the 80% isodose. The planning target volume (PTV) was defined by adding a 5mm margin to the internal target volume (ITV), the ITV corresponding to the gross tumour volume (GTV) plus a 3mm margin. CTV is considered equal to GTV. The non-understanding of the gating technique, the great number of beams and the limited breath-hold times led to the failure of some treatments. It can be explained by some patients insufficient respiratory abilities and the low dose rate of one of the beams used for treatment, thus forcing some radiation fields to be delivered in two or three times. Implementing such a technique can be limited by the patients’ physical abilities and the materials used. Some solutions were found: a training phase more intense with a coaching of the breath-hold technique more precise, or the use of an abdominal compression device.