title: Five-fraction CyberKnife radiotherapy for large brain metastases in critical areas: impact on the surrounding brain volumes circumscribed with a single dose equivalent of 14 Gy (V14) to avoid radiation necrosis.
abstract: The efficacy and toxicity of five-fraction CyberKnife radiotherapy were evaluated in patients with large brain metastases in critical areas. A total of 85 metastases in 78 patients, including tumors >30 cm(3) (4 cm in diameter) were treated with five-fraction CyberKnife radiotherapy with a median marginal dose of 31 Gy at a median prescribed isodose of 58%. Changes in the neurological manifestations, local tumor control, and adverse effects were investigated after treatment. The surrounding brain volumes circumscribed with 28.8 Gy (single dose equivalent to 14 Gy: V14) were measured to evaluate the risk of radiation necrosis. Neurological manifestations, such as motor weakness, visual disturbances and aphasia improved in 28 of 55 patients (50.9%). Local tumor control was obtained in 79 of 85 metastases (92.9%) during a median follow-up of eight months. Symptomatic edema occurred in 10 patients, and two of them (2.6%) required surgical resection because of radiation necrosis. The V14 of these patients was 3.0-19.7 cm(3). There were 16 lesions with a V14 of ≥7.0 cm(3), and two of these lesions developed extensive brain edema due to radiation necrosis. None of the patients with a V14 of <7.0 cm(3) exhibited edema requiring surgical intervention. We therefore conclude that a high rate of local tumor control and low rates of complications can be obtained after five-fraction CyberKnife radiotherapy for large metastases in critical areas. The V14 of the surrounding brain is therefore a useful indicator for the risk of radiation necrosis in patients with large metastases.
authors.affiliation: Cyber Center, Kanto Neurosurgical Hospital, 1120 Dai, Kumagaya, Saitama, 360-0804, Japan.
authors.forename: Hiroshi K
authors.initials: HK
authors.lastname: Inoue
authors.forename: Hiro
authors.initials: H
authors.lastname: Sato
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Seto
authors.forename: Kota
authors.initials: K
authors.lastname: Torikai
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Saitoh
authors.forename: Shin-ei
authors.initials: SE
authors.lastname: Noda
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001930:Brain Injuries / Q000209:etiology / Q000473:pathology* / Q000517:prevention & control*; D001932:Brain Neoplasms / Q000473:pathology / Q000556:secondary* / Q000601:surgery*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D059351:Organ Sparing Treatments / Q000379:methods; D011832:Radiation Injuries / Q000209:etiology / Q000473:pathology* / Q000517:prevention & control*; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D012062:Relative Biological Effectiveness; D016896:Treatment Outcome
keywords: V14; five-session radiosurgery; hypofractionated radiotherapy; large brain metastases; radiation necrosis