(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To study the feasibility and the effectiveness of a novel implementation of robust-optimization for skin flashing in intensity-modulated radiotherapy for breast cancer.
Methods: Two representative patients were selected for this study, one with a relatively large breast and the other with a relatively small breast. For each patient, three plans treating the breast and regional lymphatics were generated using three different skin flashing methods, including (1) a manual flash (MF) plan, with optimization on the nominal planning target volume (PTV) not extending beyond the skin, and manually post-planning opening of the MLC and jaw to obtain flash), (2) an expanded PTV (ExpPTV) plan, with optimization on an expanded PTV that included target in air beyond the skin, and (3) robust-optimized (RO) plan, using robust-optimization that simultaneously optimizes on the nominal CT dataset as well as on a simulated geometry error CT dataset. The feasibility and the effectiveness of the robust-optimization approach was investigated by comparing it with the two existing methods. The robustness of the plan against the target position variation due to respiratory motion, breast shape change, and edema was studied by simulating geometry errors of 0, 5mm, 10mm, and 15mm.
Results: When the geometry error reached 15mm, for patient #1, the PTV D95% was 90%, 95% and 95% for the MF-, ExpPTV-, and RO-plan, respectively; for patient #2, the PTV D95% was 67%, 94% and 96% for the MF-, ExpPTV-, and RO-plan, respectively. The manual flash plan showed a larger hotspot as compared to the other two types of plans. The doses to the lung and heart were comparable for all three planning techniques.
Conclusion: Using robust optimization for skin flash in breast IMRT planning is feasible. Further investigation is warranted to confirm the clinical effectiveness of this novel approach.
Keywords
Breast, Intensity Modulation, Shape Deformation
Taxonomy
TH- External beam- photons: Motion management (intrafraction)
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