Dosimetric feasibility of stereotactic ablative radiotherapy in pulmonary vein isolation for atrial fibrillation using intensity‐modulated proton therapy

Abstract

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.

Stereotactic Radiotherapy Ablation and Atrial Fibrillation: Technical Issues and Clinical Expectations Derived From a Systematic Review

“…Four studies focused on PBT, and carbon ions were used in all cases: 2 works were dosimetric ( 58 , 59 ) and one reported on in vivo dosimetry on animals ( 60 ). The last one ( 61 ) compared intensity-modulated proton therapy with XRT delivered through VMAT and helical tomotherapy.…”

“…The most recent article included on PBT, Ren et al ( 61 ), evaluated dosimetric properties of intensity-modulated proton therapy in comparison with VMAT and tomotherapy treatment planning; the prescription dose was 25 Gy in all plans. The proton-based technique resulted in a significantly reduce dose in surrounding tissues, compared to photon-based ones, in patients with AF.…”

“…In the end, it is important to remember how it is possible that a dilated heart with AF appears to have less movement than a healthy one ( 61 , 72 ): so, it is also possible that all dosimetric studies on healthy subjects are not completely suitable for the patients with real-AF and more investigations could be necessary.…”

“…In the included articles, pencil beams were used to better modulate the beam on the TV; the limit of these thin rays is a major sensibility to motion and setup errors, then the correct position of the beam’s distal edge remains unknown ( 75 ). Ren et al ( 61 ) decided to study this phenomenon in their work using a cardiac motion scan from a patient case. Nevertheless, beam rescanning and 4D dose calculation ( 58 ) or the use of in-beam PET can reduce the problem ( 60 ).…”

A pulmonary vein atlas for radiotherapy planning

“…A feasibility study using SABR to treat AF suggested this approach is effective and safe (35). As arrhythmogenic foci are commonly found at multiple PV-LA junctions in AF, invasive radiofrequency ablations typically involve the entire PV region, which has been shown to be feasible with SABR fields in a multimodality planning study (36). A phase II clinical trial testing uniform treatment to all four PV regions has recently launched and will provide preliminary safety and efficacy signals (37).…”