Composite minimax robust optimization of VMAT improves target coverage and reduces non-target dose in head and neck cancer patients

Wagenaar, Daniel A.; Kierkels, Roel G J; Free, Jeffrey; Langendijk, Johannes A.; Both, Stefan; Korevaar, Erik W

doi:10.1016/j.radonc.2019.03.019

Cited by 21 publications

(10 citation statements)

References 25 publications

(38 reference statements)

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“…Future work on estimation of stopping power ratios using dual-energy CT can help reduce the range errors found in proton radiography and reduce the required range uncertainty setting [23,35]. Additionally, future work should be extended to photon therapy where both robust optimization and a probabilistic assessment of target coverage should be used to further improve treatment [36]. This is the first study to incorporate anatomical changes and systematic and random setup and range uncertainties to determine the estimated delivered dose by means of dose mapping and accumulation using longitudinal CT imaging in IMPT HNC patients.…”

Section: Discussionmentioning

confidence: 99%

Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting

Wagenaar

Kierkels

Schaaf

et al. 2021

Radiotherapy and Oncology

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Objective: To establish optimal robust optimization uncertainty settings for clinical head and neck cancer (HNC) patients undergoing 3D image-guided pencil beam scanning (PBS) proton therapy. Methods: We analyzed ten consecutive HNC patients treated with 70 and 54.25 Gy RBE to the primary and prophylactic clinical target volumes (CTV) respectively using intensity-modulated proton therapy (IMPT). Clinical plans were generated using robust optimization with 5 mm/3% setup/range uncertainties (RayStation v6.1). Additional plans were created for 4, 3, 2 and 1 mm setup and 3% range uncertainty and for 3 mm setup and 3%, 2% and 1% range uncertainty. Systematic and random error distributions were determined for setup and range uncertainties based on our quality assurance program. From these, 25 treatment scenarios were sampled for each plan, each consisting of a systematic setup and range error and daily random setup errors. Fraction doses were calculated on the weekly verification CT closest to the date of treatment as this was considered representative of the daily patient anatomy. Results: Plans with a 2 mm/3% setup/range uncertainty setting adequately covered the primary and prophylactic CTV (V 95 ! 99% in 98.8% and 90.8% of the treatment scenarios respectively). The average organat-risk dose decreased with 1.1 Gy RBE /mm setup uncertainty reduction and 0.5 Gy RBE /1% range uncertainty reduction. Normal tissue complication probabilities decreased by 2.0%/mm setup uncertainty reduction and by 0.9%/1% range uncertainty reduction. Conclusion: The results of this study indicate that margin reduction below 3 mm/3% is possible but requires a larger cohort to substantiate clinical introduction.

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Section: Discussionmentioning

confidence: 99%

Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting

Wagenaar

Kierkels

Schaaf

et al. 2021

Radiotherapy and Oncology

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“…No robust evaluation of the VMAT plans was performed at baseline, as this was not clinical practice for photon treatment plans. Incorporation of robustness evaluation for VMAT into clinical practice might improve the target coverage on the rCT's for photon treatments as well [36]. This will have to be evaluated in following analysis.…”

Section: Discussionmentioning

confidence: 99%

Weekly robustness evaluation of intensity-modulated proton therapy for oesophageal cancer

Anakotta

Laan

Visser

et al. 2020

Radiotherapy and Oncology

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Background and purpose: Intensity-modulated proton therapy (IMPT) is expected to result in clinical benefits by lowering radiation dose to organs-at-risk (OARs). However, there are concerns about plan robustness due to motion. To address this uncertainty we evaluated the robustness of IMPT compared to the widely clinically used volumetric modulated arc therapy (VMAT) on weekly repeated computed tomographies (CT). Materials and methods: 19 patients with oesophageal cancer were evaluated. IMPT and VMAT plans were created on a planning 4-Dimensional CT (p4DCT) and evaluated on weekly repeated 4DCTs (r4DCT). In case of inadequate target coverage or unacceptable high dose to normal tissue, re-planning was performed. Dose distributions of the r4DCTs were warped to p4DCT, resulting in an estimated actual given dose (EAGD). Results: Compared to VMAT, IMPT resulted in significantly lowered dose to heart, lungs, spleen, liver and kidneys. For IMPT, target coverage was adequate (after max 1 replanning) in 17/19 cases. In two cases target coverage remained insufficient. However, in one of these patients the summed dose was insufficient (due to tumor shrinkage) while weekly coverage was adequate. For the other patient the target coverage was also insufficient by VMAT, due to large anatomical changes during treatment. For VMAT, adequate target coverage was achieved in 18/19 cases without re-planning. However, for reasons of high OAR dose re-planning was required in two cases. Conclusion: IMPT reduces the dose to OARs significantly, while achieving adequate target coverage in the majority of patients. Re-planning was necessary for both IMPT and VMAT due to anatomical changes.

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“…‘Worst case’ uncertainty scenarios (as employed in the commercial TPS we used) are sometimes criticized for being overly conservative [48]: stochastic or probabilistic approaches form an active area of research and a viable alternative [12]. To date, relatively little research has been performed on robust optimization and robustness reporting in photon therapy [49,50]: additional work in this area could facilitate fairer dosimetric comparisons between treatment modalities. Ultimately, inter- and intra-fraction variations in anatomy could also be considered as part of the robustness problem [51].…”

Section: Discussionmentioning

confidence: 99%

The impact of proton LET/RBE modeling and robustness analysis on base-of-skull and pediatric craniopharyngioma proton plans relative to VMAT

Gutiérrez

Rompokos

et al. 2019

Acta Oncologica

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Purpose: Pediatric craniopharyngioma, adult base-of-skull sarcoma and chordoma cases are all regarded as priority candidates for proton therapy. In this study, a dosimetric comparison between volumetric modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) was first performed. We then investigated the impact of physical and biological uncertainties. We assessed whether IMPT plans remained dosimetrically superior when such uncertainty estimates were considered, especially with regards to sparing organs at risk (OARs).Methodology: We studied 10 cases: four chondrosarcoma, two chordoma and four pediatric craniopharyngioma. VMAT and IMPT plans were created according to modality-specific protocols. For IMPT, we considered (i) variable RBE modeling using the McNamara model for different values of (α/β)x, and (ii) robustness analysis with ±3 mm set-up and 3.5% range uncertainties.Results: When comparing the VMAT and IMPT plans, the dosimetric advantages of IMPT were clear: IMPT led to reduced integral dose and, typically, improved CTV coverage given our OAR constraints. When physical robustness analysis was performed for IMPT, some uncertainty scenarios worsened the CTV coverage but not usually beyond that achieved by VMAT. Certain scenarios caused OAR constraints to be exceeded, particularly for the brainstem and optical chiasm. However, variable RBE modeling predicted even more substantial hotspots, especially for low values of (α/β)x. Variable RBE modeling often prompted dose constraints to be exceeded for critical structures.Conclusion: For base-of-skull and pediatric craniopharyngioma cases, both physical and biological robustness analyses should be considered for IMPT: these analyses can substantially affect the sparing of OARs and comparisons against VMAT. All proton RBE modeling is subject to high levels of uncertainty, but the clinical community should remain cognizant possible RBE effects. Careful clinical and imaging follow-up, plus further research on end-of-range RBE mitigation strategies such as LET optimization, should be prioritized for these cohorts of proton patients.

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Composite minimax robust optimization of VMAT improves target coverage and reduces non-target dose in head and neck cancer patients

Cited by 21 publications

References 25 publications

Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting

Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting

Weekly robustness evaluation of intensity-modulated proton therapy for oesophageal cancer

The impact of proton LET/RBE modeling and robustness analysis on base-of-skull and pediatric craniopharyngioma proton plans relative to VMAT

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