Dosimetric Feasibility Of Stereotactic Ablative Radiotherapy In Pulmonary Vein Isolation For Atrial Fibrillation Using Intensity-Modulated Proton Therapy

Purpose To evaluate dosimetric properties of intensity-modulated proton therapy (IMPT) for simulated treatment planning in patients with atrial fibrillation (AF) targeting left atrial-pulmonary vein junction (LA-PVJ), in comparison with volumetric-modulated arc therapy (VMAT) and helical tomotherapy (TOMO).Methods Ten thoracic 4D-CT scans with respiratory motion and one with cardiac motion were used for the study. Ten respiratory 4D-CTs were planned with VMAT, TOMO, and IMPT for simulated AF. Targets at the LA-PVJ were defined as wide-area circumferential ablation line. A single fraction of 25 Gy was prescribed to all plans. The interplay effects from cardiac motion were evaluated based on the cardiac 4D-CT scan. Dose-volume histograms (DVHs) of the ITV and normal tissues were compared. Statistical analysis was evaluated via one-way Repeated-Measures ANOVA and Friedman's test with Bonferroni's multiple comparisons test.Results The median volume of ITV was 8.72cc. All plans had adequate target coverage (V-23.75Gy >= 99%). Compared with VMAT and TOMO, IMPT resulted in significantly lower dose of most normal tissues. For VMAT, TOMO, and IMPT plans, D-mean of the whole heart was 5.52 +/- 0.90 Gy, 5.89 +/- 0.78 Gy, and 3.01 +/- 0.57 Gy (P < 0.001), mean dose of pericardium was 4.74 +/- 0.76 Gy, 4.98 +/- 0.62 Gy, and 2.59 +/- 0.44 Gy (P < 0.001), and D-0.03cc of left circumflex artery (LCX) was 13.96 +/- 5.45 Gy, 14.34 +/- 5.91 Gy, and 8.43 +/- 7.24 Gy (P < 0.001), respectively. However, no significant advantage for one technique over the others was observed when examining the D-0.03cc of esophagus and main bronchi.Conclusions IMPT targeting LA-PVJ for patients with AF has high potential to reduce dose to surrounding tissues compared to VMAT or TOMO. Motion mitigation techniques are critical for a particle-therapy approach.