Importance of protocol target definition on the ability to spare normal tissue: an IMRT and 3D-CRT planning comparison for intraorbital tumors

Abstract

Purpose/Objective: With increasing availability of intensity modulated radiation therapy (IMRT) the radiation oncology community is challenged to prove superiority of IMRT over three-dimensional radiation therapy (3D-CRT). To attain this goal the design of protocol specifications that permit optimum use of this new modality is desirable. The orbit is a complex anatomical site for RT planning due to the close proximity of tumors and organs at risk and the irregular, horseshoe-shaped, concave geometry of intraorbital target volumes. The goal of this study was 1) to evaluate realistic expectations as to lens sparing capabilities of 3D-CRT/IMRT for different intraorbital tumor configurations, 2) to investigate the potential added benefits of IMRT, and 3) to evaluate the impact of dose/volume specification changes on the ability to spare organs at risk.