Multimodality
therapy for gastrointestinal (GI)
cancers carries considerable risk for toxicity; even single-modality
radiation therapy in this population carries with it a daunting side effect profile. Supportive care can certainly mitigate some of the morbidity, but there remain numerous associated acute and late complications that can compromise the
therapy and ultimately the outcome.
Gastrointestinal cancers inherently occur amid visceral organs that are particularly sensitive to
radiotherapy, creating a very narrow therapeutic window for aggressive cell kill with minimal normal tissue damage.
Radiation therapy is a critical component of locoregional control, but its use has historically been limited by toxicity concerns, both real and perceived. Fundamental to this is the fact that long-term clinical experience with radiation in GI
cancers derives almost entirely from 2-dimensional radiation (plain x-ray-based planning) and subsequently 3-dimensional conformal radiation. The recent use of intensity-modulated photon-based techniques is not well represented in most of the landmark chemoradiation trials. Furthermore, the elusive search for efficacious but tolerable local
therapy in GI
malignancies raises the possibility that
proton radiotherapy's physical and dosimetric differences relative to conventional
therapy may make it better suited to the challenge. In many sites, local recurrences after chemoradiation pose a particular challenge, and
reirradiation in these sites may be done successfully with
proton radiotherapy.