Clinical implementation of 4D Guidance during lung cancer treatment with radiation therapy

Abstract: Radiotherapy is one of the main treatment for lung cancer. This technique relies on killing the tumor cells by focusing electron or photon beam in the area. A recent type form of treatment called, Stereotactic Body Radiation Therapy consists in the delivery of very high dose in a few number of fractions, which leads to an increased importance of the precision of the dose delivery. During the workflow of the radiotherapy treatment, the planning part is a fundamental step: in particularly the structure contouring and the dose optimization. In the particular case of lung cancer treatment, the definition of the target volume is very complex due to tumor motions that can lead to errors during the treatment and inadequate dose delivery. There are several sources of motions which can be of different origin, associated to random or systematic errors, and result in interfraction or intrafraction differences. One of the most challenging source of motion is the breathing motion which is patient-, fraction-, time-dependent. Respiration can indeed change at every cycle depending on the patient psychological and physiological state of mind. In order to provide an efficient treatment, those tumor motions need to be analyzed precisely and taken into account at all the steps of the workflow: from the planning to the actual treatment delivery. Motion management tools have been developed to help physicians, radiologists and technologists provide a better treatment and try to control as much as possible the position of the beam versus the target. One of them is a software that is able to acquire a four dimensional Cone Beam Computed Tomography. It then uses those respiration-correlated images to provide a more accurate position correction at the beginning of the treatment thanks to a better and more precise visualization of the tumor during the entire breathing cycle. Yet, this tool is not completely understood by the medical staff and there is a lack of guideline in the way the workflow should be adapted to take the best advantages of this technique. It is not necessarily well used and this can be at risk for the patients in some situations. Some studies have shown the benefits of the use of a 4D guidance to better control the treatment relative to the tumor motions, however they have been carried out using a specific technique that is not necessarily used homogeneously by all institutions. Understanding and comparing the different way it is possible to use 4D Guidance has not raised interest among the publishing institutions. This project questions this particular technique: which are the different methods used during patient treatment? Is there a method that is proven to be better and should be used broadly? If yes, how can the medical staff be trained more efficiently so that they can feel more comfortable and understand better the benefit of the technique? This consists in a structured analysis to study a motion management technique with a broader view point involving a meta-analysis of the literature, a questionnaire survey as well as a seminar with medical staff gathering all profiles of users. This evaluation aims at improving the use of 4D guidance to better compensate the motion challenges during the treatment of moving tumors. This work enables to gain knowledge and visibility on the technique of 4D guidance and particularly how it can be implemented in clinical routine safely and efficiently. Among all the methods identified, some main methods have been selected and can be advised to new institution willing to treat using 4D motion management. A concept for training professional in several steps is also designed with this purpose.