Program Information
Dosimetric Comparison of Prone Versus Supine Positioning for Adjuvant Breast Radiation Therapy
C Pope1*, L Hayes2 , J Rella3 , B Ruiz4 , B O'Connor5 , J Yang6 , (1,5) Beth Isreal Deaconess Hospital Plymouth, Plymouth, MA, (2) Cone Health Cancer Center, Greensboro, NC, (3-4,6) Alliance Oncology, Newburyport, MA
Presentations
SU-E-T-307 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:The prone treatment position has been used to reduce ipsilateral lung and heart dose in left breast radiation. We conducted a retrospective study to evaluate the difference in the dosimetry between prone and supine treatment positions.
Methods:Eight left breast cancer patients were simulated in both the supine and prone positions as a pretreatment evaluation for the optimal treatment position. Treatment plans were created for all patients in both the supine and prone positions using a field in field three dimensional planning technique. Prescribed dose was 45 Gy delivered by two tangential photon fields. Irradiated volume (IV) was evaluated by V50, V100, and dose to lung and heart by V5, V10, V20, and the mean dose were evaluated.
Results:All dosimetry metrics for both the supine and prone plans met our internal normal structure guidelines which are based on Quantec data. The average IVs (50% and 100%) were 2223cc and 1361cc prone, 2315cc and 1315cc supine. The average ipsilateral lung Mean dose (0.83Gy prone vs 5.8Gy supine), V5 (1.6% prone vs 20.9% supine), V10 (0.78% prone vs 15% supine) and V20 (0.36% prone vs 11% supine) were significantly lower in prone position. Heart Mean dose (1.4Gy prone vs 2.9Gy supine), V10 (1.4% prone vs 5.0% supine) and V20 (0.4% prone vs 3.5% supine) were found improved for all patients except one where the mean dose was the same and all other values were improved.
Conclusion:The prone position offer preferable dosimetry for all patients planned in our study. These patients were chosen based on the physician’s belief that they would benefit from prone treatment either because they had large pendulous breasts or due to the amount of heart seen in the field on CT simulation.
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