Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer

Isak Wahlstedt; Nicolaus Andratschke; Claus P Behrens; Stefanie Ehrbar; Hubert S Gabryś; Helena Garcia Schüler; Matthias Guckenberger; Abraham George Smith; Stephanie Tanadini-Lang; José D Tascón-Vidarte; Ivan R Vogelius; Janita E van Timmeren

doi:10.1016/j.radonc.2022.03.013

Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer

Isak Wahlstedt, Nicolaus Andratschke, Claus P Behrens, Stefanie Ehrbar, Hubert S Gabryś, Helena Garcia Schüler, Matthias Guckenberger, Abraham George Smith, Stephanie Tanadini-Lang, José D Tascón-Vidarte, Ivan R Vogelius, Janita E van Timmeren

Abstract

BACKGROUND AND PURPOSE: MR-guided radiotherapy (MRgRT) allows real-time beam-gating to compensate for intra-fractional target position variations. This study investigates the dosimetric impact of beam-gating and the impact of PTV margin on prostate coverage for prostate cancer patients treated with online-adaptive MRgRT.

MATERIALS AND METHODS: 20 consecutive prostate cancer patients were treated with online-adaptive MRgRT SBRT with 36.25 Gy in 5 fractions (PTV D95% ≥ 95% (N = 5) and PTV D95% ≥ 100% (N = 15)). Sagittal 2D cine MRIs were used for gating on the prostate with a 3 mm expansion as the gating window. We computed motion-compensated dose distributions for (i) all prostate positions during treatment (simulating non-gated treatments) and (ii) for prostate positions within the gating window (gated treatments). To evaluate the impact of PTV margin on prostate coverage, we simulated coverage with smaller margins than clinically applied both for gated and non-gated treatments. Motion-compensated fraction doses were accumulated and dose metrics were compared.

RESULTS: We found a negligible dosimetric impact of beam-gating on prostate coverage (median of 0.00 Gy for both D95% and Dmean). For 18/20 patients, prostate coverage (D95% ≥ 100%) would have been ensured with a prostate-to-PTV margin of 3 mm, even without gating. The same was true for all but one fraction.

CONCLUSION: Beam-gating has negligible dosimetric impact in online-adaptive MRgRT of prostate cancer. Accounting for motion, the clinically used prostate-to-PTV margin could potentially be reduced from 5 mm to 3 mm for 18/20 patients.

Original language	English
Journal	Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
Volume	170
Pages (from-to)	205-212
Number of pages	8
ISSN	0167-8140
DOIs	https://doi.org/10.1016/j.radonc.2022.03.013
Publication status	Published - May 2022

Keywords

Humans
Magnetic Resonance Imaging
Male
Prostatic Neoplasms/diagnostic imaging
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Image-Guided
Radiotherapy, Intensity-Modulated

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Wahlstedt, I., Andratschke, N., Behrens, C. P., Ehrbar, S., Gabryś, H. S., Schüler, H. G., Guckenberger, M., Smith, A. G., Tanadini-Lang, S., Tascón-Vidarte, J. D., Vogelius, I. R., & van Timmeren, J. E. (2022). Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer. Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, 170, 205-212. https://doi.org/10.1016/j.radonc.2022.03.013

Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer. / Wahlstedt, Isak; Andratschke, Nicolaus; Behrens, Claus P et al.
In: Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, Vol. 170, 05.2022, p. 205-212.

Research output: Contribution to journal › Journal article › Research › peer-review

Wahlstedt, I, Andratschke, N, Behrens, CP, Ehrbar, S, Gabryś, HS, Schüler, HG, Guckenberger, M, Smith, AG, Tanadini-Lang, S, Tascón-Vidarte, JD, Vogelius, IR & van Timmeren, JE 2022, 'Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer', Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, vol. 170, pp. 205-212. https://doi.org/10.1016/j.radonc.2022.03.013

@article{c32adffedea84863a077b0ddebd27781,

title = "Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer",

abstract = "BACKGROUND AND PURPOSE: MR-guided radiotherapy (MRgRT) allows real-time beam-gating to compensate for intra-fractional target position variations. This study investigates the dosimetric impact of beam-gating and the impact of PTV margin on prostate coverage for prostate cancer patients treated with online-adaptive MRgRT.MATERIALS AND METHODS: 20 consecutive prostate cancer patients were treated with online-adaptive MRgRT SBRT with 36.25 Gy in 5 fractions (PTV D95% ≥ 95% (N = 5) and PTV D95% ≥ 100% (N = 15)). Sagittal 2D cine MRIs were used for gating on the prostate with a 3 mm expansion as the gating window. We computed motion-compensated dose distributions for (i) all prostate positions during treatment (simulating non-gated treatments) and (ii) for prostate positions within the gating window (gated treatments). To evaluate the impact of PTV margin on prostate coverage, we simulated coverage with smaller margins than clinically applied both for gated and non-gated treatments. Motion-compensated fraction doses were accumulated and dose metrics were compared.RESULTS: We found a negligible dosimetric impact of beam-gating on prostate coverage (median of 0.00 Gy for both D95% and Dmean). For 18/20 patients, prostate coverage (D95% ≥ 100%) would have been ensured with a prostate-to-PTV margin of 3 mm, even without gating. The same was true for all but one fraction.CONCLUSION: Beam-gating has negligible dosimetric impact in online-adaptive MRgRT of prostate cancer. Accounting for motion, the clinically used prostate-to-PTV margin could potentially be reduced from 5 mm to 3 mm for 18/20 patients.",

keywords = "Humans, Magnetic Resonance Imaging, Male, Prostatic Neoplasms/diagnostic imaging, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted, Radiotherapy, Image-Guided, Radiotherapy, Intensity-Modulated",

author = "Isak Wahlstedt and Nicolaus Andratschke and Behrens, {Claus P} and Stefanie Ehrbar and Gabry{\'s}, {Hubert S} and Sch{\"u}ler, {Helena Garcia} and Matthias Guckenberger and Smith, {Abraham George} and Stephanie Tanadini-Lang and Tasc{\'o}n-Vidarte, {Jos{\'e} D} and Vogelius, {Ivan R} and {van Timmeren}, {Janita E}",

year = "2022",

month = may,

doi = "10.1016/j.radonc.2022.03.013",

language = "English",

volume = "170",

pages = "205--212",

journal = "Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology",

issn = "0167-8140",

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T1 - Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer

AU - Wahlstedt, Isak

AU - Andratschke, Nicolaus

AU - Behrens, Claus P

AU - Ehrbar, Stefanie

AU - Gabryś, Hubert S

AU - Schüler, Helena Garcia

AU - Guckenberger, Matthias

AU - Smith, Abraham George

AU - Tanadini-Lang, Stephanie

AU - Tascón-Vidarte, José D

AU - Vogelius, Ivan R

AU - van Timmeren, Janita E

PY - 2022/5

Y1 - 2022/5

N2 - BACKGROUND AND PURPOSE: MR-guided radiotherapy (MRgRT) allows real-time beam-gating to compensate for intra-fractional target position variations. This study investigates the dosimetric impact of beam-gating and the impact of PTV margin on prostate coverage for prostate cancer patients treated with online-adaptive MRgRT.MATERIALS AND METHODS: 20 consecutive prostate cancer patients were treated with online-adaptive MRgRT SBRT with 36.25 Gy in 5 fractions (PTV D95% ≥ 95% (N = 5) and PTV D95% ≥ 100% (N = 15)). Sagittal 2D cine MRIs were used for gating on the prostate with a 3 mm expansion as the gating window. We computed motion-compensated dose distributions for (i) all prostate positions during treatment (simulating non-gated treatments) and (ii) for prostate positions within the gating window (gated treatments). To evaluate the impact of PTV margin on prostate coverage, we simulated coverage with smaller margins than clinically applied both for gated and non-gated treatments. Motion-compensated fraction doses were accumulated and dose metrics were compared.RESULTS: We found a negligible dosimetric impact of beam-gating on prostate coverage (median of 0.00 Gy for both D95% and Dmean). For 18/20 patients, prostate coverage (D95% ≥ 100%) would have been ensured with a prostate-to-PTV margin of 3 mm, even without gating. The same was true for all but one fraction.CONCLUSION: Beam-gating has negligible dosimetric impact in online-adaptive MRgRT of prostate cancer. Accounting for motion, the clinically used prostate-to-PTV margin could potentially be reduced from 5 mm to 3 mm for 18/20 patients.

AB - BACKGROUND AND PURPOSE: MR-guided radiotherapy (MRgRT) allows real-time beam-gating to compensate for intra-fractional target position variations. This study investigates the dosimetric impact of beam-gating and the impact of PTV margin on prostate coverage for prostate cancer patients treated with online-adaptive MRgRT.MATERIALS AND METHODS: 20 consecutive prostate cancer patients were treated with online-adaptive MRgRT SBRT with 36.25 Gy in 5 fractions (PTV D95% ≥ 95% (N = 5) and PTV D95% ≥ 100% (N = 15)). Sagittal 2D cine MRIs were used for gating on the prostate with a 3 mm expansion as the gating window. We computed motion-compensated dose distributions for (i) all prostate positions during treatment (simulating non-gated treatments) and (ii) for prostate positions within the gating window (gated treatments). To evaluate the impact of PTV margin on prostate coverage, we simulated coverage with smaller margins than clinically applied both for gated and non-gated treatments. Motion-compensated fraction doses were accumulated and dose metrics were compared.RESULTS: We found a negligible dosimetric impact of beam-gating on prostate coverage (median of 0.00 Gy for both D95% and Dmean). For 18/20 patients, prostate coverage (D95% ≥ 100%) would have been ensured with a prostate-to-PTV margin of 3 mm, even without gating. The same was true for all but one fraction.CONCLUSION: Beam-gating has negligible dosimetric impact in online-adaptive MRgRT of prostate cancer. Accounting for motion, the clinically used prostate-to-PTV margin could potentially be reduced from 5 mm to 3 mm for 18/20 patients.

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KW - Magnetic Resonance Imaging

KW - Male

KW - Prostatic Neoplasms/diagnostic imaging

KW - Radiotherapy Dosage

KW - Radiotherapy Planning, Computer-Assisted

KW - Radiotherapy, Image-Guided

KW - Radiotherapy, Intensity-Modulated

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DO - 10.1016/j.radonc.2022.03.013

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SN - 0167-8140

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JO - Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology

JF - Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology

ER -

Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer

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