Authors:
Matthew Mouawad, Matthew Mouawad, Owen Lailey, Per Rugaard Poulsen, Melissa O'Neil, Muriel Brackstone, Michael Lock, Michael Lock, Brian Yaremko, Brian Yaremko, Olga Shmuilovich, Olga Shmuilovich, Anat Kornecki, Anat Kornecki, Ilanit Ben Nachum, Ilan (...)
Matthew Mouawad, Matthew Mouawad, Owen Lailey, Per Rugaard Poulsen, Melissa O'Neil, Muriel Brackstone, Michael Lock, Michael Lock, Brian Yaremko, Brian Yaremko, Olga Shmuilovich, Olga Shmuilovich, Anat Kornecki, Anat Kornecki, Ilanit Ben Nachum, Ilanit Ben Nachum, Giulio Muscedere, Giulio Muscedere, Kalan Lynn, Kalan Lynn, Scott J. Karnas, Frank S. Prato, R. Terry Thompson, R. Terry Thompson, Stewart Gaede
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Abstract:
Abstract Background and purpose To quantify intra-fraction tumor motion using imageguidance and implanted fiducial markers to determine if a 5 mm planning-target-volume (PTV) margin is sufficient for early stage breast cancer patients receiving neoadjuvant stereotactic ablative radiotherapy (SABR). Materials and methods A HydroMark© (Mammotome) fiducial was implanted at the time of biopsy adjacent to the tumor. Sixty-one patients with 62 tumours were treated prone using a 5 mm PTV margin. Motion was quantified using two methods (separate pat (...)
Abstract Background and purpose To quantify intra-fraction tumor motion using imageguidance and implanted fiducial markers to determine if a 5 mm planning-target-volume (PTV) margin is sufficient for early stage breast cancer patients receiving neoadjuvant stereotactic ablative radiotherapy (SABR). Materials and methods A HydroMark© (Mammotome) fiducial was implanted at the time of biopsy adjacent to the tumor. Sixty-one patients with 62 tumours were treated prone using a 5 mm PTV margin. Motion was quantified using two methods (separate patient groups): 1) difference in 3D fiducial position pre- and post-treatment cone-beam CTs (CBCTs) in 18 patients receiving 21 Gy/1fraction (fx); 2) acquiring 2D triggered-kVimages to quantify 3D intra-fraction motion using a 2D-to-3D estimation method for 44 tumours receiving 21 Gy/1fx (n = 22) or 30 Gy/3fx (n = 22). For 2), motion was quantified by calculating the magnitude of intra-fraction positional deviation from the pretreatment CBCT. PTV margins were derived using van Herkian analysis. Results The average ± standard deviation magnitude of motion across patients was 1.3 ± 1.15 mm Left/Right (L/R), 1.0 ± 0.9 mm Inferiorly/Superiorly (I/S), and 1.8 ± 1.5 mm Anteriorly/Posteriorly (A/P). 85/105 (81%) treatment fractions had dominant anterior motion. 6/62patients (9.7%) had mean intra-fraction motion during any fraction > 5 mm in any direction, with 4 in the anterior direction. Estimated PTV margins for single and three-fx patients in the L/R, I/S, and A/P directions were 6.0x4.1x5.9 mm and 4.5x2.9x4.3 mm, respectively. Conclusion Our results suggest that a 5 mm PTV margin is sufficient for the I/S and A/P directions if a lateral kV image is acquired immediately before treatment. For the L/R direction, either further immobilization or a larger margin is required.
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