• Alina Santiago, Urszula Jelen, Filippo Ammazzalorso, Rita Engenhart-Cabillic, Peter Fritz, Werner Mühlnickel, Wolfgang Enghardt, Michael Baumann, and Andrea Wittig.
• University of Marburg, Department of Radiotherapy and Radiation Oncology, Germany. Electronic address: santiago@staff.uni-marburg.de.
• Radiother Oncol. 2013 Oct 1; 109 (1): 45-50.

PurposeTo investigate scanned-beam proton dose distribution reproducibility in the lung under high frequency jet ventilation (HFJV).Materials And MethodsFor 11 patients (12 lesions), treated with single-fraction photon stereotactic radiosurgery under HFJV, scanned-beam proton plans were prepared with the TRiP98 treatment planning system using 2, 3-4 and 5-7 beams. The planning objective was to deliver at least 95% of the prescription of 33 Gy (RBE) to 98% of the PTV. Plans were subsequently recomputed on localization CT scans. Additionally, for selected cases, the effects of range uncertainties were investigated.ResultsMedian GTV V(98%) was 98.7% in the original 2-field plans and 93.7% in their recomputation (p=0.039). The respective values were 99.0% and 98.0% (p=0.039) for the 3-4-field plans and 100.0% and 99.6% (p=0.125) for the 5-7-field plans. CT calibration uncertainties of ±3.5% led to a GTV V(98%) reduction below 1.5 percentual points in most cases and reaching 3 percentual points for 2-field plans with beam undershoot.ConclusionsThrough jet ventilation, reproducible tumor fixation for proton radiotherapy of lung lesions is achievable, ensuring excellent target coverage in most cases. In few cases, non-optimal patient setup reproducibility induced density changes across beam entrance channels, leading to dosimetric deterioration between planning and delivery.Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

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