Abstract
The use of IMRT in the treatment of breast cancer is increasing across the U.S. as a result of the improvements provided in dose homogeneity and normal tissue avoidance. The application of IMRT offers reduced soft tissue toxicity in isolated breast treatment and the potential for improved local-regional control without an increase in lung and heart toxicity in those requiring loco-regional treatment. When standard tangential fields are used to define the target volume, the focus of IMRT is primarily to optimize dose homogeneity. Although long term outcome studies are needed to make definitive statements, many have already accepted this treatment approach as a preferred method of treatment delivery. However, when dose conformality becomes a primary focus, many uncertainties arise that require additional study prior to widespread adoption. By generating highly conformal fields with severe dose gradients, the accuracy of treatment delivery becomes increasingly dependant on set up error and breathing motion. This is not an issue when standard tangents are used for isolated breast treatment as the generous field design allows the target to remain in the field despite inter or intra-fraction motion. However, this is a critical issue when dose shaping with the goal of maximizing target coverage and normal tissue avoidance. Future investigation will need to address these challenges before IMRT can be considered for widespread adoption. Additionally, long term followup is needed to determine whether the improvements in dose homogeneity and conformality will translate into improvements in disease control and/or a reduction in toxicity.