Three-fraction CyberKnife radiotherapy for brain metastases in critical areas: referring to the risk evaluating radiation necrosis and the surrounding brain volumes circumscribed with a single dose equivalence of 14 Gy (V14) |
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Authors: | Hiroshi K. Inoue Ken-ichi Seto Akihiko Nozaki Kota Torikai Yoshiyuki Suzuki Jun-ichi Saitoh Shin-ei Noda Takashi Nakano |
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Affiliation: | 1.Cyber Center, Kanto Neurosurgical Hospital, 1120 Dai, Kumagaya, Saitama, 360-0804, Japan;2.Gunma University Heavy-ion Medical Research Center, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan;3.Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan |
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Abstract: | The efficacy and toxicity of three-fraction CyberKnife radiotherapy were evaluated in patients with brain metastases in critical areas. One hundred and fifty-nine metastases in 145 patients including tumors >10 cm3 were treated with three-fraction CyberKnife radiotherapy with a median marginal dose of 27 Gy at a median prescribed isodose of 60%. Changes in the neurological manifestations, local tumor control and adverse effects were investigated after treatment. The surrounding brain volumes circumscribed with 23.1 Gy (single dose equivalence of 14 Gy: V14) were measured to evaluate the risk of adverse effects. Neurological manifestations, such as motor weakness, visual disturbances and aphasia improved in 26 of 97 patients (26.8%). Local tumor control was obtained in 137 of 143 metastases (95.8%) during a median follow-up of 7 months. Nine patients had symptomatic edema and three of them (2.1%) required surgical resection because of radiation necrosis. The V14 of these patients was 4.6–31.5 cm3. There were 35 lesions with a V14 of 7 cm3 or more and three of them developed extensive brain edema due to radiation necrosis. None of the patients with a V14 of <7 cm3 exhibited edema requiring an operation. We therefore conclude that a high rate of local tumor control and low rates of complications are obtained after three-fraction CyberKnife radiotherapy for metastases in critical areas. The V14 of the surrounding brain therefore seems to be a useful indicator for the risk evaluation of radiation necrosis in patients with larger metastases. |
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Keywords: | brain metastases hypofractionated radiotherapy three-session radiosurgery radiation necrosis V14 |
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