Motion management in gastrointestinal cancers.

The presence of tumor and organ motions complicates the planning and delivery of radiotherapy for gastrointestinal cancers. Without proper accounting of the movements, target volume could be under-dosed and the nearby normal critical organs could be over-dosed. This situation is further exacerbated by the close proximity of abdominal tumors to many normal organs at risk (OARs). A number of strategies have been developed to deal with tumor and organ motions in radiotherapy. This article presents a review of the techniques used in the evaluation, quantification, and management of tumor and organ motions for radiotherapy of gastrointestinal cancers.