title: Tumour Movement in Proton Therapy: Solutions and Remaining Questions: A Review.
abstract: Movement of tumours, mostly by respiration, has been a major problem for treating lung cancer, liver tumours and other locations in the abdomen and thorax. Organ motion is indeed one component of geometrical uncertainties that includes delineation and target definition uncertainties, microscopic disease and setup errors. At present, minimising motion seems to be the easiest to implement in clinical practice. If combined with adaptive approaches to correct for gradual anatomical variations, it may be a practical strategy. Other approaches such as repainting and tracking could increase the accuracy of proton therapy delivery, but advanced 4D solutions are needed. Moreover, there is a need to perform clinical studies to investigate which approach is the best in a given clinical situation. The good news is that existing and emerging technology and treatment planning systems as will without doubt lead in the forthcoming future to practical solutions to tackle intra-fraction motion in proton therapy. These developments may also improve motion management in photon therapy as well.
authors.affiliation: Department of Oncology, Experimental Radiation Oncology, KU Leuven-University of Leuven, B-3000 Leuven, Belgium. dirk.deruysscher@uzleuven.be.
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ruysscher
authors.affiliation: Center of Molecular Imaging, Radiotherapy and Oncology, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, B-1200 Brussels, Belgium. edmond.sterpin@uclouvain.be.
authors.forename: Edmond
authors.initials: E
authors.lastname: Sterpin
authors.affiliation: Department of Oncology, Experimental Radiation Oncology, KU Leuven-University of Leuven, B-3000 Leuven, Belgium. karin.haustermans@uzleuven.be.
authors.forename: Karin
authors.initials: K
authors.lastname: Haustermans
authors.affiliation: Department of Oncology, Experimental Radiation Oncology, KU Leuven-University of Leuven, B-3000 Leuven, Belgium. tom.depuydt@uzleuven.be.
authors.forename: Tom
authors.initials: T
authors.lastname: Depuydt
keywords: adaptive radiotherapy; proton therapy; tumour movement