1.5 T MR-linac planning study to compare two different strategies of rectal boost irradiation

Bonomo, Pierluigi; Russo, Monica Lo; Nachbar, Marcel; Boeke, Simon; Gatidis, Sergios; Zips, Daniel; Thorwarth, Daniela; Gani, Cihan

doi:10.1016/j.ctro.2020.11.016

Cited by 16 publications

(8 citation statements)

References 35 publications

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“…With the advent of MRI-Linac hybrid devices it has become possible to considerably reduce planning target volume margins as treatment plans can be adapted to the anatomy of the day based on daily MRI scans. Several studies have shown that planning target volumes required to cover the remaining intrafractional motion with or without rectal filling can be reduced to 4 mm using an online adaptive workflow [2] , [6] , [9] . The present study demonstrates that the addition of rectal ultrasound gel results in more accurate target volume definition in rectal cancer.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to being able to use the superior soft tissue contrast of the MRI during treatment, the MRI-Linac also allows the treatment plan to be adapted daily to the anatomy of the day. These advantages allow the safety margins for rectal cancer dose escalation to be reduced to a few millimeters instead of 1 cm or more (Bonomo, Lo Russo et al 2021, Eijkelenkamp, Boekhoff et al 2021. At the same time, with such small margins accurate target volume definition becomes more crucial.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation

Russo¹,

Nachbar²,

Barry³

et al. 2023

Clinical and Translational Radiation Oncology

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation

Russo¹,

Nachbar²,

Barry³

et al. 2023

Clinical and Translational Radiation Oncology

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“…The use of MRgRT has raised the quality of all those treatments for which soft tissue visualization is essential, particularly suitable for precision treatments when the targets are close to risky structures and even more when high fractional doses are to be delivered ( 4 , 7 , 9 , 53 , 54 ). MRgRT performed with the Unity Linac allows through the ATS workflow to recalculate and reoptimize the plan using a syCT generated from the daily MRI.…”

Section: Discussionmentioning

confidence: 99%

Improving the clinical workflow of a MR-Linac by dosimetric evaluation of synthetic CT

et al. 2022

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Adaptive radiotherapy performed on the daily magnetic resonance imaging (MRI) is an option to improve the treatment quality. In the adapt-to-shape workflow of 1.5-T MR-Linac, the contours of structures are adjusted on the basis of patient daily MRI, and the adapted plan is recalculated on the MRI-based synthetic computed tomography (syCT) generated by bulk density assignment. Because dosimetric accuracy of this strategy is a priority and requires evaluation, this study aims to explore the usefulness of adding an assessment of dosimetric errors associated with recalculation on syCT to the clinical workflow. Sixty-one patients, with various tumor sites, treated using a 1.5-T MR-Linac were included in this study. In Monaco V5.4, the target and organs at risk (OARs) were contoured, and a reference CT plan that contains information about the outlined contours, their average electron density (ED), and the priority of ED assignment was generated. To evaluate the dosimetric error of syCT caused by the inherent approximation within bulk density assignment, the reference CT plan was recalculated on the syCT obtained from the reference CT by forcing all contoured structures to their mean ED defined on the reference plan. The dose–volume histogram (DVH) and dose distribution of the CT and syCT plan were compared. The causes of dosimetric discrepancies were investigated, and the reference plan was reworked to minimize errors if needed. For 54 patients, gamma analysis of the dose distribution on syCT and CT show a median pass rate of 99.7% and 98.5% with the criteria of 3%/3 mm and 2%/2 mm, respectively. DVH difference of targets and OARs remained less than 1.5% or 1 Gy. For the remaining patients, factors (i.e., inappropriate ED assignments) influenced the dosimetric agreement of the syCT vs. CT reference DVH by up to 21%. The causes of the errors were promptly identified, and the DVH dosimetry was realigned except for two lung treatments for which a significant discrepancy remained. The recalculation on the syCT obtained from the planning CT is a powerful tool to assess and decrease the minimal error committed during the adaptive plan on the MRI-based syCT.

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“…As an interim report and safety analysis, this study has certain limitations. Firstly, with the rapid development of adaptive radiotherapy during the study, the patients who received short-course radiotherapy may bene t more from the MRI-Linac [24], which can provide online treatment MRI images and instruct oncologists to precisely target tumors. Secondly, some patients did not undergo surgery due to cCR, which could cause di culties for the primary endpoint evaluation in the future.…”

Section: Discussionmentioning

confidence: 99%

The Safety of an MRI Simulation-guided Boost after Short-course Preoperative Radiotherapy for Unresectable Rectal Cancer (SUNRISE): Interim Analysis of a Randomized Phase II Trial

Liu

Shi

et al. 2022

Preprint

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Purpose The safety of an MRI simulation-guided boost after short-course preoperative radiotherapy (SCPRT) for unresectable rectal cancer is assessed with a planned interim analysis. Methods and materials Patients diagnosed with clinical stage T3-4 or regional lymph node-positive disease with positive mesorectal fascia (MRF) or T4b disease evaluated by pelvic MRI were randomly assigned to the SCPRT-boost group (25 Gy over 5 fractions plus 4 Gy delivered to the gross tumor volume, followed by four cycles of chemotherapy) or preoperative chemoradiotherapy group (50 Gy over 25 fractions with concurrent chemotherapy). Then, patients received total mesorectal excision surgery after preoperative treatment. The primary endpoint was the R0 resection rate. The interim analysis was performed when 42 patients completed their assigned treatments. Results From October 2018 to November 2019, a total of 43 patients were enrolled, and 42 patients were included in the interim analysis. During preoperative therapy, grade 3 or above toxicities were observed in 10/21 (47.6%) patients in the experimental group, and 4/21 (19.0%) patients in the control group. A total of 17 (81.0%) and 13 (61.9%) patients in the experimental group and control group underwent surgery, respectively. Overall, 69.7% of the patients achieved R0 resection or clinical complete response (cCR) in the intention-to-treat analysis. Surgery-related adverse complications were observed in 2 patients (11.8%) in the experimental group and 1 patient (7.7%) in the control group. Conclusion Our results show that the toxicity of an MRI simulation-guided boost dose after short-course preoperative radiotherapy (SCPRT) for unresectable rectal cancer is acceptable. Thus, this clinical trial will be continued as planned.

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1.5 T MR-linac planning study to compare two different strategies of rectal boost irradiation

Abstract: Highlights MRI reveals shrinkage of primary tumours during long-course chemoradiotherapy. Intra-fraction motion was assessed by 1.5 T MR-Linac. Adaptive MR-guided boost to GTV with reduced margin revealed better rectum sparing.

Cited by 16 publications

References 35 publications

Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation

Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation

Improving the clinical workflow of a MR-Linac by dosimetric evaluation of synthetic CT

The Safety of an MRI Simulation-guided Boost after Short-course Preoperative Radiotherapy for Unresectable Rectal Cancer (SUNRISE): Interim Analysis of a Randomized Phase II Trial

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