SU-E-P-09: Feasibility of Axillary Target Coverage Utilizing High Tangent Prone Breast Radiation

Abstract

Purpose: To evaluate the ability to treat level I and level II axillary lymph nodes utilizing a high tangent prone breast radiotherapy technique. Methods: Twenty-one patients were treated with whole breast radiation utilizing a prone technique. Retrospectively, axillary nodes were contoured as levels I and low lying level II with the intent of elective nodal coverage. Treatment plans were designed as tangential fields with the superior border set to cover the contoured axillary volume (high tangents). Dose-volume histograms (DVH) were evaluated for axillary, breast, lung and heart (for left breast treatments) coverage. The percent volume receiving greater than or equal to 95% of the prescribed dose (V95) was obtained for the breast and axillary regions. Results: The 95% isodose line encompassed on average 98.0% of breast volumes (range, 93.2 to 100.0%). The mean V95 for the level I and level II axillary regions were 99.5% (range, 98.3 to 100.0%) and 97.4% (range, 92.5 to 100.0%), respectively. The mean percent volume of the ipsilateral lung receiving greater than 20 Gy was 7.7% (range, 4.0 to 13.4%), and the percent volume of the heart receiving greater than 40 Gy was 0.57% (range, 0 to 2.1%). Conclusion: These results imply that prone breast radiation with high tangents is an effective and safe technique for the treatment of level I and level II axilla in addition to breast volumes. With increasing trends to limit axillary dissections in sentinel node positive patients, radiotherapy techniques to adequately cover nodal volumes has become more important. With historic data that suggested lower coverage in a prone position, we present techniques to adequately cover elective nodal volumes with good success.