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A Novel Technique for the Planning and Treatment of Deep Seated Breast Cavity Boosts

D Pearson

D Pearson1*, (1) University of Toledo, Toledo, OH


SU-I-GPD-T-491 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: A novel technique has been developed for the planning and treatment of external beam, deep seated breast cavity boosts, which leads to a more conformal dose distribution around the lumpectomy cavity PTV. Due to cavity depth, electron therapy may not be optimal for this group of patients. We compared this new technique to the traditional technique of reduced tangents. Five breast patients were evaluated in this study; each was planning with the traditional reduced tangent technique and the arc & tangent technique.

Methods: Our new technique utilizes a conformal arc, typically around 70-90 degrees in length, to compliment the reduced tangents. A comparison of the dose disruption for both techniques is shown in figure 1. Both plans were optimized to give equivalent PTV coverage. Various isodose volumes were calculated, specifically where the prescribed dose spilled outside of the PTV. RTOG conformity indices were also calculated for the 10 plans.

Results: An example of the improvements in the dose distribution is shown in figure 1 in the supporting document. The addition of the conformal arc substantially increases dose conformity to the target and reduces the volume of prescription dose spilling out of the PTV. The RTOG CI reduced from 2.679 to 1.157 when average over the 5 patients. The volume of the dose outside of the target, RTOG CI, heart and ipsilateral lung dose are shown in table 1 in the supporting document.

Conclusion: The new technique of tangents combined with a conformal arc showed itself to be an attractive alternative to reduced tangents alone. The main advantage was a significant improvement in conformity with less 100% and 105% isodose outside of the volume.

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