Combined modulated electron and photon beams planned by a Monte-Carlo-based optimization procedure for accelerated partial breast irradiation

Palma, Bianey; Ureba, Ana; Salguero, Francisco J.; Arráns, R.; Sánchez, Carlos Míguez; Zurita, Amadeo Walls; Romero-Hermida, M. I.; Leal, Antonio

doi:10.1088/0031-9155/57/5/1191

Cited by 31 publications

(45 citation statements)

References 29 publications

(45 reference statements)

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“…By delivering MERT plans with a standard photon MLC, the potential arises for seamless mixed electron–photon delivery without interrupting treatment delivery between modality changes. Indeed, mixed‐beam electron–photon radiotherapy (MBRT) plans have been shown to offer additional degrees of freedom to influence the trade‐off between normal tissue dose and target coverage …”

Section: Introductionmentioning

confidence: 99%

Robust mixed electron–photon radiation therapy optimization

2019

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Purpose Mixed beam electron–photon radiation therapy (MBRT) is an emerging technique that has the potential to reduce dose to normal tissue while improving target coverage for cancer sites with superficial tumors. Advances in optimization algorithms and robotic linear accelerators have made the creation and delivery of complex MBRT plans realistic without the need for special additional collimators, devices, or resetup of the patient. However, no study has been performed on the robustness of MBRT dose distributions to patient setup errors. Intensity‐modulated delivery of other charged particles such as protons have been shown to require robust planning techniques to maintain adequate target coverage under positioning errors. We therefore assess the sensitivity of MBRT treatment plans to positioning uncertainties when created under the traditional planning target volume (PTV)‐based planning paradigm and present a novel optimization model for the creation of robust MBRT plans. Methods The column generation method was applied to robust MBRT treatment planning by deriving the pricing problem for stochastic and “worst case” minimax optimization models, two common formulations of robustness. Robust treatment plans were created for two patient cases representative of the cancer sites which stand to benefit from MBRT: soft tissue sarcoma (STS) irradiation and chest wall irradiation with deep‐seated internal mammary, axillary, and supraclavicular nodes (CW‐N). For both patient cases, beamlet dose distributions for electrons and photons were generated for positioning shifts in six directions, ±5mm(xfalse^,yfalse^,zfalse^) in addition to a nominal unshifted scenario, for a total of seven sets of beamlets. Robust plans were created by specifying dose coverage constraints to the clinical target volume (CTV), as opposed to the PTV. Comparisons were performed against traditional PTV‐based plans created with a single set of unshifted beamlets. Results The dose distributions of traditional PTV‐based MBRT plans showed significant degradation in target coverage homogeneity when patient positioning errors were considered. For both cancer sites, cold spots below 95% and hot spots above 108% of the prescription dose appeared within the CTV when shifting the patient by 5 mm, corresponding to the margin added to the CTV to form the PTV. In contrast, CTV‐based robust plans created with the new optimization model maintained target coverage within the 95%–108% limits, for all positioning errors. Conclusion The quality of MBRT treatment plans created using a traditional PTV‐based optimization model was highly sensitive to patient positioning errors. For both patient cases, positioning errors resulted in perturbations to the nominal dose distributions which would have rendered PTV‐based plans clinically unacceptable. In contrast, CTV‐based robust plans were able to maintain adequate target coverage under all positioning error scenarios considered. We therefore conclude that to ensure the fidelity of the dose distribution delivered to the pat...

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Section: Introductionmentioning

confidence: 99%

Robust mixed electron–photon radiation therapy optimization

2019

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“…If photon beams are added to electron beams, called mixed beam radiotherapy (MBRT), then this restriction in the target depth is removed. It was shown for targets with at least some superficial part that treatment plan quality of coplanar step and shoot MBRT plans with simultaneously optimized photon and electron beams is substantially improved compared to IMRT and VMAT plans, because of the additional DoF of two different particle types . At the same time, clinical workflow could be maintained, because photon and electron beams are usually both available on the same conventional treatment unit and using the pMLC also for electron beam collimation means that no accessory is required to be attached to the treatment unit.…”

Section: Introductionmentioning

confidence: 99%

Part 2: Dynamic mixed beam radiotherapy (DYMBER): Photon dynamic trajectories combined with modulated electron beams

et al. 2018

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“…In certain PBI cases, the dose distribution and OAR exposure may be optimized by the combination of photon and electron fields. [23][24][25] Only 1 contemporary study has reported the use of sole electron fields for PBI. 26,27 Altogether 40 patients with relatively small breasts received electron irradiation of a dose of 25 Â 2 Gy; this technique resulted in the lowest rate (17.5%) of fat necrosis of grade I to III, as compared with that in the brachytherapy and WBI arms.…”

Section: Clinical Outcomementioning

confidence: 99%

Partial breast radiotherapy with simple teletherapy techniques

et al. 2015

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A prospective pilot study of partial breast irradiation (PBI) with conventional vs hypofractionated schedules was set out. The study aimed to determine efficacy, acute and late side effects, and the preference of photon vs electron irradiation based on individual features. Patients were enrolled according to internationally accepted guidelines on PBI. Conformal radiotherapy plans were generated with both photon and electron beams, and the preferred technique based on dose homogeneity and the radiation exposure of healthy tissues was applied. For electron dose verification, a special phantom was constructed. Patients were randomized for fractionation schedules of 25 × 2 vs 13 × 3Gy. Skin and breast changes were registered at the time of and ≥1 year after the completion of radiotherapy. Dose homogeneity was better with photons. If the tumor bed was located in the inner quadrants, electron beam gave superior results regarding conformity and sparing of organ at risk (OAR). If the tumor was situated in the lateral quadrants, conformity was better with photons. A depth of the tumor bed ≥3.0cm predicted the superiority of photon irradiation (odds ratio [OR] = 23.6, 95% CI: 5.2 to 107.5, p < 0.001) with >90% sensitivity and specificity. After a median follow-up of 39 months, among 72 irradiated cases, 1 local relapse out of the tumor bed was detected. Acute radiodermatitis of grade I to II, hyperpigmentation, and telangiectasia developed ≥1 year after radiotherapy, exclusively after electron beam radiotherapy. The choice of electrons or photons for PBI should be based on tumor bed location; the used methods are efficient and feasible.

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Combined modulated electron and photon beams planned by a Monte-Carlo-based optimization procedure for accelerated partial breast irradiation

Cited by 31 publications

References 29 publications

Robust mixed electron–photon radiation therapy optimization

Robust mixed electron–photon radiation therapy optimization

Part 2: Dynamic mixed beam radiotherapy (DYMBER): Photon dynamic trajectories combined with modulated electron beams

Partial breast radiotherapy with simple teletherapy techniques

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