Program Information
Should Proton Radiotherapy with Pencil Beam Scanning Be the Treatment of Choice for Left Chest Wall Irradiation?
S O'Reilly*, C Shillington , A Darafsheh , B Teo , G Freedman , A Kassaee , UNIVERSITY OF PENNSYLVANIA, Philadelphia, Pennsylvania
Presentations
SU-I-GPD-T-123 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: Radiotherapy in the thoracic region can lead to increased risk of cardiac injury or mortality and radiation pneumonitis. We investigate the use of proton therapy with pencil beam scanning technique (PBS) in treatment of the left chest wall and its advantages relative to tradition photon therapy. We also explore if PBS should be the dominant choice by calculating the normal tissue complication probability (NTCP) for lung and heart.
Methods: PBS and conventional photon therapy treatment plans were generated for five left chest wall patients, who were previously treated with either photon therapy or double scattering proton therapy (DS). The PBS plan beam arrangement consisted of a single left anterior oblique field, while the 3D conformal were typical tangential beam arrangements.
Results: Lower lung and heart doses were achieved with the PBS plans, while maintaining or achieving better target coverage. Average mean heart doses were 957.46 cGy (226.5 – 2347.6) and 56 cGy (40.8 – 76.4) for the photon and proton plans, respectively. The average V5 for the ipsilateral lung for the photon plan was 52.24% (34.65 – 76.9) and 33.94% (15.88 – 47.9) for the PBS plan. The average ipsilateral lung V20 was 35.74% (19.58 – 66.4) for photons and 15.49% (6.45 – 22.95) for protons. Two patients had unfavorable anatomy for 3D conformal, one being clinically treated with volumetric modulated arc therapy and one with DS. Comparing their clinically treated plans with the PBS plans, the PBS plans still resulted in heart and lung sparing. Higher hotspots in the treatment volume were attributed to the PBS plans.
Conclusion: Significant dose sparing to cardiac structures and lungs is achieved with PBS planning when compared to conventional photon plans. The dose volume histogram and NTCP analysis supports the use of PBS as the modality of choice.
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