Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac

Keizer, Daan M. de Muinck; Kerkmeijer, Linda G.W.; Willigenburg, T.; Lier, Astrid L.H.M.W. van; Hartogh, M.D. den; Zyp, Jochem R.N. van der Voort van; Breugel, Eline N. de Groot-van; Raaymakers, B W; Lagendijk, J J W; Boer, J.C.J. de

doi:10.1016/j.radonc.2020.06.044

Cited by 88 publications

(94 citation statements)

References 23 publications

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“…In contrast, margins were never exceeded in the left-right axis. Intrafraction motion amplitude was highest in the antero-posterior axis and lowest in the left-right axis, in accordance with the motions that could be expected from rectum and bladder filling and with previous findings [8,11,[23][24][25]. The Calypso Ò data showed that the median offset of prostate during SBRT was close to 0, with a maximum of 2.3 mm (Table 2).…”

Section: Discussionsupporting

confidence: 90%

Single-fraction prostate stereotactic body radiotherapy: Dose reconstruction with electromagnetic intrafraction motion tracking

Jaccard

Ehrbar

Miralbell

et al. 2021

Radiotherapy and Oncology

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To reconstruct the dose delivered during single-fraction urethra-sparing prostate stereotactic body radiotherapy (SBRT) accounting for intrafraction motion monitored by intraprostatic electromagnetic transponders (EMT). Methods: We analyzed data of 15 patients included in the phase I/II ''ONE SHOT" trial and treated with a single fraction of 19 Gy to the planning target volume (PTV) and 17 Gy to the urethra planning risk volume. During delivery, prostate motion was tracked with implanted EMT. SBRT was interrupted when a 3mm threshold was trespassed and corrected unless the offset was transient. Motion-encoded reconstructed (MER) plans were obtained by splitting the original plans into multiple sub-beams with isocenter shifts based on recorded EMT positions, mimicking prostate motion during treatment. We analyzed intrafraction motion and compared MER to planned doses. Results: The median EMT motion range (±SD) during delivery was 0.26 ± 0.09, 0.22 ± 0.14 and 0.18 ± 0. 10 cm in the antero-posterior, supero-inferior, and left-right axes, respectively. Treatment interruptions were needed for 8 patients because of target motion beyond limits in the antero-posterior (n = 6) and/or supero-inferior directions (n = 4). Comparing MER vs. original plan there was a median relative dose difference of À1.9% (range, À7.9 to À1.0%) and of +0.5% (À0.3-1.7%) for PTV D 98% and D 2% , respectively. The clinical target volume remained sufficiently covered with a median D 98% difference of À0.3% (À1.6-0.5%). Bladder and rectum dosimetric parameters showed significant differences between original and MER plans, but mostly remained within acceptable limits. Conclusions: The dosimetric impact of intrafraction prostate motion was minimal for target coverage for single-fraction prostate SBRT with real-time electromagnetic tracking combined with beam gating.

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Section: Discussionsupporting

confidence: 90%

Single-fraction prostate stereotactic body radiotherapy: Dose reconstruction with electromagnetic intrafraction motion tracking

Jaccard

Ehrbar

Miralbell

et al. 2021

Radiotherapy and Oncology

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“…Also, we believe that the full potential of MR-Linac systems lies in achieving these very small PTV margins that are not possible with conventional systems. Based on our prostate motion analyses, 3 to 4 mm margins are sufficient for current prostate cancer treatment without intra-fraction adaptation [12] . Enlarging the PTV margin in our study to i.e.…”

Section: Discussionmentioning

confidence: 96%

“…Prior investigations by our department showed that the geometrical accuracy of the Elekta MR-Linac system is on average 0.3 mm (range 0.2–0.4 mm) [6] . Concerning prostate motion, we have developed an accurate soft tissue prostate tracking algorithm with a mean error of 0.07 mm (SD 0.22 mm) [11] , [12] . Combined with new treatment planning systems developed at our department that facilitate online (intrafraction) replanning to account for anatomy shifts and changes, we assumed that a 1 mm PTV margin is achievable [9] , [13] , [14] .…”

Section: Methodsmentioning

confidence: 99%

Focal salvage treatment for radiorecurrent prostate cancer: A magnetic resonance-guided stereotactic body radiotherapy versus high-dose-rate brachytherapy planning study

Willigenburg¹,

Beld²,

Hes

et al. 2020

Physics and Imaging in Radiation Oncology

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Background and Purpose: Magnetic resonance imaging (MRI)-guided focal salvage high-dose-rate brachytherapy (FS-HDR-BT) is one of the treatment options for radiorecurrent localized prostate cancer. However, due to the invasive nature of the treatment, not all patients are eligible. Magnetic resonance linear accelerator (MR-Linac) systems open up new treatment possibilities and could potentially replace FS-HDR-BT treatment. We conducted a planning study to investigate the feasibility of delivering a single 19 Gy dose to the recurrent lesion using a 1.5 Tesla MR-Linac system. Materials and Methods: Thirty patients who underwent FS-HDR-BT were included. The clinical target volume (CTV) encompassed the visible lesion plus a 5 mm margin. Treatment plans were created for a 1.5 Tesla MR-Linac system using a 1 mm planning target volume (PTV) margin. A dose of 19 Gy was prescribed to ≥ 95% of the PTV. In case this target could not be reached, i.e. when organs-at-risk (OAR) constraints were violated, a dose of ≥ 17 Gy to ≥ 90% of the PTV was accepted. MR-Linac plans were compared to clinical FS-HDR-BT plans. Results: Target dose coverage was achieved in 14/30 (47%) FS-HDR-BT plans and 17/30 (57%) MR-Linac plans, with comparable median D95% and D90%. In FS-HDR-BT plans, a larger volume reached ≥ 150% of the prescribed dose. Urethra D10%, rectum D1cm 3 , and rectum D2cm 3 were lower in the FS-HDR-BT plans, while bladder dose was comparable for both modalities. Conclusion: Single fraction treatment of recurrent prostate cancer lesions may be feasible using stereotactic body radiotherapy (SBRT) on a MR-Linac system.

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“…In this scenario, the use of rectal spacers for mitigating prostate motion represents a helpful tool to maximize the safety and accuracy of extremely hypofractionated treatments for prostate cancer [41,42]. To date, the use of this device has been safely reported by Alongi et al in a series of 20 patients who received MR-guided prostate SBRT using rectal hydrogel spacer.…”

Section: Mr-guided Radiotherapy: Present Evidencementioning

confidence: 99%

MR-Guided Hypofractionated Radiotherapy: Current Emerging Data and Promising Perspectives for Localized Prostate Cancer

Cuccia

Corradini

Mazzola

et al. 2021

Cancers

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In this review we summarize the currently available evidence about the role of hybrid machines for MR-guided radiotherapy for prostate stereotactic body radiotherapy. Given the novelty of this technology, to date few data are accessible, but they all report very promising results in terms of tolerability and preliminary clinical outcomes. Most of the studies highlight the favorable impact of on-board magnetic resonance imaging as a means to improve target and organs at risk identification with a consequent advantage in terms of dosimetric results, which is expected to relate to a more favorable toxicity pattern. Still, the longer treatment time per session may potentially affect the patient’s compliance to the treatment, although first quality of life assessment studies have reported substantial tolerability and no major impact on quality of life. Finally, in this review we hypothesize some future scenarios of further investigation, based on the possibility to explore the superior anatomy visualization and the role of daily adapted treatments provided by hybrid MR-Linacs.

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Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac

Cited by 88 publications

References 23 publications

Single-fraction prostate stereotactic body radiotherapy: Dose reconstruction with electromagnetic intrafraction motion tracking

Single-fraction prostate stereotactic body radiotherapy: Dose reconstruction with electromagnetic intrafraction motion tracking

Focal salvage treatment for radiorecurrent prostate cancer: A magnetic resonance-guided stereotactic body radiotherapy versus high-dose-rate brachytherapy planning study

MR-Guided Hypofractionated Radiotherapy: Current Emerging Data and Promising Perspectives for Localized Prostate Cancer

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