Radiosurgery with flattening-filter-free techniques in the treatment of brain metastases

Tonndorf-Martini, Eric; Schramm, Oliver; Rhein, B.; Stefanowicz, Sarah; Kappes, Jutta; Hoffmann, Hans; Lindel, Katja; Debus, Jürgen; Rieken, Stefan

doi:10.1007/s00066-016-1012-x

Cited by 14 publications

(19 citation statements)

References 44 publications

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“…However, several investigators have assessed the dosimetric comparison between FFF beams and FF beams, and the results showed that dose distributions achieved with FFF beams are similar to those with FF beams [ 16 , 18 ]. J. Rieber, et al [ 19 ] have compared plan quality of radiosurgery in brain metastases using 3-dimensional conventional technique, and showed that FFF beams provides similar plan quality with slightly reduced dose spillage to normal brain.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric superiority of flattening filter free beams for single-fraction stereotactic radiosurgery in single brain metastasis

et al. 2016

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For single-fraction stereotactic radiosurgery (SRS) using linac in brain metastases, more accurate treatment delivery with higher tumor absorbed doses and lower absorbed doses to normal tissues remains an enormous challenge. The purpose of this study was to investigate the dosimetric superiority in flattening filter free beams (FFF) for volumetric modulated arc therapy (VMAT) in single brain metastasis. 68 patients with single brain metastasis were included in this study. Every patient was subjected to VMAT treatment plans using 6 MV standard flattened (FF) beams (VMAT_FF) and 6 MV FFF beams (VMAT_FFF) with single fraction doses of 20 Gy. Dosimetric evaluation was performed by analysis of target coverage, dose gradients, beam-on time (BOT), gantry speed and number of monitor units (MU). There were no differences between VMAT_FF and VMAT_FFF plans in conformity and MU. VMAT_FFF plans showed obvious superiority in homogeneity, dose gradients and efficiency. For the mean BOT, VMAT_FFF plans provided a significant decrease by 42.8% compared with VMAT_FF. By the use of FFF beams, brain irradiation was minimized with about 2% reductions in low-dose regions (about 5-10 Gy). FFF beams not only resulted in more efficiency by reducing treatment time, but also provided further brain sparing compared to traditional techniques for SRS in single brain metastasis.

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Section: Introductionmentioning

confidence: 99%

Dosimetric superiority of flattening filter free beams for single-fraction stereotactic radiosurgery in single brain metastasis

et al. 2016

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“…Furthermore, a lower peripheral dose is a unique characteristic in FFF beams due to the decrease of photon head scatter, head leakage and leaf transmission [38]. It has been demonstrated that the dose gradients in FFF beams were superior to FF beams and that FFF provides further brain sparing compared to traditional techniques for SRS in single brain metastasis [39,40].…”

Section: Contouring and Treatment Planning Srsmentioning

confidence: 99%

LINAC based stereotactic radiosurgery for multiple brain metastases: guidance for clinical implementation

et al. 2019

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Introduction: Stereotactic radiosurgery (SRS) is a promising treatment option for patients with multiple brain metastases (BM). Recent technical advances have made LINAC based SRS a patient friendly technique, allowing for accurate patient positioning and a short treatment time. Since SRS is increasingly being used for patients with multiple BM, it remains essential that SRS be performed with the highest achievable quality in order to prevent unnecessary complications such as radionecrosis. The purpose of this article is to provide guidance for high-quality LINAC based SRS for patients with BM, with a focus on single isocenter non-coplanar volumetric modulated arc therapy (VMAT). Methods: The article is based on a consensus statement by the study coordinators and medical physicists of four trials which investigated whether patients with multiple BM are better palliated with SRS instead of whole brain radiotherapy (WBRT): A European trial (NCT02353000), two American trials and a Canadian CCTG lead intergroup trial (CE.7). This manuscript summarizes the quality assurance measures concerning imaging, planning and delivery. Results: To optimize the treatment, the interval between the planning-MRI (gadolinium contrastenhanced, maximum slice thickness of 1.5 mm) and treatment should be kept as short as possible (< two weeks). The BM are contoured based on the planning-MRI, fused with the planning-CT. GTV-PTV margins are minimized or even avoided when possible. To maximize efficiency, the preferable technique is single isocenter (non-)coplanar VMAT, which delivers high doses to the target with maximal sparing of the organs at risk. The use of flattening filter free photon beams ensures a lower peripheral dose and shortens the treatment time. To bench mark SRS treatment plan quality, it is advisable to compare treatment plans between hospitals. Conclusion: This paper provides guidance for quality assurance and optimization of treatment delivery for LINAC-based radiosurgery for patients with multiple BM.

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“…The same approach was applied, expanding the GTV by 3 mm to create the PTV for SI-VMAT for delivery at the Elekta Versa HD linac installed at our facility, where no such intrafractional motion compensation is currently available. The choice of respective margin width was done following literature recommendations and established institutional practice (8,13,14).…”

Section: Imaging and Target Definitionmentioning

confidence: 99%

“…For VMAT plans, beam-on time was calculated by RayStation from the number of monitor units (MUs), at an underlying variable dose rate of 500-1,400 MU/min for 6-MV flattening filter-free (FFF) irradiation. An additional 5 min were added to beam-on time to account for patient setup and position verification via kV-ConeBeam CT (CBCT), in accordance with data previously published for our institution (8).…”

Section: Comparison Metricsmentioning

confidence: 99%

“…In general, a separate isocenter would be required for every treated lesion, which requires repeated position verification during treatment delivery. Additionally, treatment using sequential multifield 3D-conformal radiotherapy (3DCRT) or dynamic conformal arc therapy (DCAT) would lead to a significantly increased integral dose to the healthy brain (HB) (7,8).…”

Section: Introductionmentioning

confidence: 99%

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Single-Isocenter Volumetric Modulated Arc Therapy vs. CyberKnife M6 for the Stereotactic Radiosurgery of Multiple Brain Metastases

et al. 2020

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Introduction: Stereotactic radiosurgery (SRS) is becoming more frequently used for patients with multiple brain metastases (BMs). Single-isocenter volumetric modulated arc therapy (SI-VMAT) is an emerging alternative to dedicated systems such as CyberKnife (CK). We present a dosimetric comparison between CyberKnife M6 and SI-VMAT, planned at RayStation V8B, for the simultaneous SRS of five or more BM.Patients and Methods: Twenty treatment plans of CK-based single-session SRS to ≥5 brain metastases were replanned using SI-VMAT for delivery at an Elekta VersaHD linear accelerator. Prescription dose was 20 or 18 Gy, conformally enclosing at least 98% of the total planning target volume (PTV), with PTV margin-width adapted to the respective SRS technique. Comparatively analyzed quality metrics included dose distribution to the healthy brain (HB), including different isodose volumes, conformity, and gradient indices. Estimated treatment time was also compared.Results: Median HB isodose volumes for 3, 5, 8, 10, and 12 Gy were consistently smaller for CK-SRS compared to SI-VMAT (p < 0.001). Dose falloff outside the target volume, as expressed by the gradient indices GI_high and GI_low, was consistently steeper for CK-SRS compared to SI-VMAT (p < 0.001). CK-SRS achieved a median GI_high of 3.1 [interquartile range (IQR), 2.9-1.3] vs. 5.0 (IQR 4.3-5.5) for SI-VMAT (p < 0.001). For GI_low, the results were 3.0 (IQR, 2.9-3.1) for CK-SRS vs. 5.6 (IQR, 4.3-5.5) for SI-VMAT (p < 0.001). The median conformity index (CI) was 1.2 (IQR, 1.1-1.2) for CK-SRS vs. 1.5 (IQR, 1.4-1.7) for SI-VMAT (p < 0.001). Estimated treatment time was shorter for SI-VMAT, yielding a median of 13.7 min (IQR, 13.5-14.0) compared to 130 min (IQR, 114.5-154.5) for CK-SRS (p < 0.001).El Shafie et al. SI-VMAT vs. CyberKnife for Multiple BMConclusion: SI-VMAT offers enhanced treatment efficiency in cases with multiple BM, as compared to CyberKnife, but requires compromise regarding conformity and integral dose to the healthy brain. Additionally, delivery at a conventional linear accelerator (linac) may require a larger PTV margin to account for delivery and setup errors. Further evaluations are warranted to determine whether the detected dosimetric differences are clinically relevant. SI-VMAT could be a reasonable alternative to a dedicated radiosurgery system for selected patients with multiple BM.

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Radiosurgery with flattening-filter-free techniques in the treatment of brain metastases

Abstract: SRS in FFF mode is time efficient and provides similar plan quality with the opportunity of slightly reduced dose exposure to healthy brain tissue when compared to SRS in FF mode. Clinical outcomes appear promising and show only modest treatment-related toxicity.

Cited by 14 publications

References 44 publications

Dosimetric superiority of flattening filter free beams for single-fraction stereotactic radiosurgery in single brain metastasis

Dosimetric superiority of flattening filter free beams for single-fraction stereotactic radiosurgery in single brain metastasis

LINAC based stereotactic radiosurgery for multiple brain metastases: guidance for clinical implementation

Single-Isocenter Volumetric Modulated Arc Therapy vs. CyberKnife M6 for the Stereotactic Radiosurgery of Multiple Brain Metastases

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