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      HyperArc VMAT planning for single and multiple brain metastases stereotactic radiosurgery: a new treatment planning approach

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          Abstract

          Purpose

          The HyperArc VMAT (HA-VMAT) planning approach was newly developed to fulfill the demands of dose delivery for brain metastases stereotactic radiosurgery. We compared the dosimetric parameters of the HA-VMAT plan with those of the conventional VMAT (C-VMAT).

          Material and methods

          For 23 patients (1–4 brain metastases), C-VMAT and HA-VMAT plans with a prescription dose of 20–24 Gy were retrospectively generated, and dosimetric parameters for PTV (homogeneity index, HI; conformity index, CI; gradient index, GI) and brain tissue (V 2Gy-V 16Gy) were evaluated. Subsequently, the physical characteristics (modulation complexity score for VMAT, MCSV; Monitor unit, MU) of both treatment approaches were compared.

          Results

          HA-VMAT provided higher HI (1.41 ± 0.07 vs. 1.24 ± 0.07, p < 0.01), CI (0.93 ± 0.02 vs. 0.90 ± 0.05, p = 0.01) and lower GI (3.06 ± 0.42 vs. 3.91 ± 0.55, p < 0.01) values. Moderate-to-low dose spreads (V 4Gy-V 16Gy) were significantly reduced ( p < 0.01) in the HA-VMAT plan over that of C-VMAT. HA-VMAT plans resulted in more complex MLC patterns (lower MCSV, p < 0.01) and higher MU ( p < 0.01).

          Conclusions

          HA-VMAT plans provided significantly higher conformity and rapid dose falloff with respect to the C-VMAT plans.

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          Most cited references20

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          Radiotherapeutic and surgical management for newly diagnosed brain metastasis(es): An American Society for Radiation Oncology evidence-based guideline.

          To systematically review the evidence for the radiotherapeutic and surgical management of patients newly diagnosed with intraparenchymal brain metastases.
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            Stereotactic radiosurgery plus whole brain radiotherapy versus radiotherapy alone for patients with multiple brain metastases.

            Multiple brain metastases are a common health problem, frequently diagnosed in patients with cancer. The prognosis, even after treatment with whole brain radiation therapy (WBRT), is poor with average expected survivals less than 6 months. Retrospective series of stereotactic radiosurgery have shown local control and survival benefits in case series of patients with solitary brain metastases. We hypothesized that radiosurgery plus WBRT would provide improved local brain tumor control over WBRT alone in patients with two to four brain metastases. Patients with two to four brain metastases (all < or =25 mm diameter and known primary tumor type) were randomized to initial brain tumor management with WBRT alone (30 Gy in 12 fractions) or WBRT plus radiosurgery. Extent of extracranial cancer, tumor diameters on MRI scan, and functional status were recorded before and after initial care. The study was stopped at an interim evaluation at 60% accrual. Twenty-seven patients were randomized (14 to WBRT alone and 13 to WBRT plus radiosurgery). The groups were well matched to age, sex, tumor type, number of tumors, and extent of extracranial disease. The rate of local failure at 1 year was 100% after WBRT alone but only 8% in patients who had boost radiosurgery. The median time to local failure was 6 months after WBRT alone (95% confidence interval [CI], 3.5-8.5) in comparison to 36 months (95% CI, 15.6-57) after WBRT plus radiosurgery (p = 0.0005). The median time to any brain failure was improved in the radiosurgery group (p = 0.002). Tumor control did not depend on histology (p = 0.85), number of initial brain metastases (p = 0.25), or extent of extracranial disease (p = 0.26). Patients who received WBRT alone lived a median of 7.5 months, while those who received WBRT plus radiosurgery lived 11 months (p = 0.22). Survival did not depend on histology or number of tumors, but was related to extent of extracranial disease (p = 0.02). There was no neurologic or systemic morbidity related to stereotactic radiosurgery. Combined WBRT and radiosurgery for patients with two to four brain metastases significantly improves control of brain disease. WBRT alone does not provide lasting and effective care for most patients.
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              Management of brain metastases.

              Brain metastases occur in 20-40% of patients with cancer and their frequency has increased over time. Lung, breast and skin (melanoma) are the commonest sources of brain metastases, and in up to 15% of patients the primary site remains unknown. After the introduction of MRI, multiple lesions have outnumbered single lesions. Contrast-enhanced MRI is the gold standard for the diagnosis. There are no pathognomonic features on CT or MRI that distinguish brain metastases from primary malignant brain tumors or nonneoplastic conditions: therefore a tissue diagnosis by biopsy should be always obtained in patients with unknown primary tumor before undergoing radiotherapy and/or chemotherapy. Some factors are prognostically important: a high Performance Status, a solitary brain metastasis, an absence of systemic metastases, a controlled primary tumor and a younger age. Based on these factors, subgroups of patients with different prognosis have been identified (RPA class I, II, III). Symptomatic therapy includes corticosteroids to reduce vasogenic cerebral edema and anticonvulsants to control seizures. In patients with newly diagnosed brain metastases prophylactic anticonvulsants should not be used routinely. The combination of surgery and whole-brain radiotherapy (WBRT) is superior to WBRT alone for the treatment of single brain metastasis in patients with limited or absent systemic disease and good neurological condition. Complete surgical resection allows a relief of intracranial hypertension, seizures and focal neurological deficits. Radiosurgery, alone or in conjunction with WBRT, yields results which are comparable to those reported after surgery followed by WBRT, provided that lesion's diameter does not exceed 3-3.5 cm. Radiosurgery offers the potential of treating patients with surgically inaccessible metastases. Still controversial is the need for WBRT after surgery or radiosurgery: local control seems better with the combined approach, but overall survival does not improve. Late neurotoxicity in long surviving patients after WBRT is not negligible; to avoid this complication patients with favorable prognostic factors must be treated with conventional schedules of RT, and monitoring of cognitive functions is important. WBRT alone is the treatment of choice in patients with single brain metastasis not amenable to surgery or radiosurgery, and with an active systemic disease, and in patients with multiple brain metastases. A small subgroup of these latter may benefit from surgery. The response rate of brain metastases to chemotherapy is similar to the response rate of the primary tumor and extracranial metastases, some tumor types being more chemosensitive (small cell lung carcinoma, breast carcinoma, germ cell tumors). New radiosensitizers and cytotoxic or cytostatic agents, and innovative technique of drug delivery are being investigated.
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                Author and article information

                Contributors
                ueyama-si@mc.pref.osaka.jp
                ueda-yo@mc.pref.osaka.jp
                akino-radonc@umin.net
                misaki.hashimoto@hosp-yao.osaka.jp
                masaoka-ak@mc.pref.osaka.jp
                hirata-ta@mc.pref.osaka.jp
                miyazaki-ma@mc.pref.osaka.jp
                koizumi@sahs.med.osaka-u.ac.jp
                (+81)-6-6945-1181 , teshima-te@mc.pref.osaka.jp
                Journal
                Radiat Oncol
                Radiat Oncol
                Radiation Oncology (London, England)
                BioMed Central (London )
                1748-717X
                29 January 2018
                29 January 2018
                2018
                : 13
                : 13
                Affiliations
                [1 ]Department of Radiation Oncology, Osaka International Cancer Institute, 3-1-69 Otemae, Chuo-ku, Osaka, 537-8567 Japan
                [2 ]ISNI 0000 0004 0373 3971, GRID grid.136593.b, Department of Medical Physics and Engineering, , Osaka University Graduate School of Medicine, ; 1-7 Yamadaoka, Suita, Osaka, 565-0871 Japan
                [3 ]ISNI 0000 0004 0403 4283, GRID grid.412398.5, Division of Medical Physics, Oncology Center, , Osaka University Hospital, ; 2-2 (D10) Yamadaoka, Suita, Osaka, 565-0871 Japan
                [4 ]Department of Radiation Oncology, Yao Municipal Hospital, 1-3-1 Ryuge-cho, Yao, Osaka, 581-0069 Japan
                Article
                948
                10.1186/s13014-017-0948-z
                5789615
                29378610
                6e6b1129-5d1f-4d53-b6b3-49d834c4917c
                © The Author(s). 2018

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 2 October 2017
                : 18 December 2017
                Funding
                Funded by: Health and Labour Sciences Research Grants for Promotion of Cancer Control Programs
                Award ID: H26-Cancer Policy-General-014
                Award Recipient :
                Funded by: JSPS KAKENHI Grant
                Award ID: 15H04913
                Award ID: 17K15816
                Award Recipient :
                Categories
                Research
                Custom metadata
                © The Author(s) 2018

                Oncology & Radiotherapy
                brain metastases,stereotactic radiosurgery,vmat,hyperarc,dosimetric parameter

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