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A review of published reports of spinal cord tolerance after stereotactic body radiation therapy was performed. This report presents several dose-response models, recommends dose limits for the spinal cord, and outlines standards for future reporting Spinal cord tolerance data for stereotactic body radiation therapy (SBRT) were extracted from published reports, reviewed, and modelled. For de novo SBRT delivered in 1 to 5 fractions, the following spinal cord point maximum doses (D max) are estimated to be associated with a 1% to 5% risk of radiation myelopathy (RM): 12.4 to 14.0 Gy in 1 fraction, 17.0 Gy in 2 fractions, 20.3 Gy in 3 fractions, 23.0 Gy in 4 fractions, and 25.3 Gy in 5 fractions. For reirradiation SBRT delivered in 1 to 5 fractions, reported factors associated with a lower risk of RM include cumulative thecal sac equivalent dose in 2 Gy fractions with an alpha/beta of 2 (EQD2 2) D max 70 Gy; SBRT thecal sac EQD2 2 D max 25 Gy, thecal sac SBRT EQD2 2 D max to cumulative EQD2 2 D max ratio 0.5, and a minimum time interval to reirradiation of !5 months. Larger studies containing complete institutional cohorts with dosimetric data of

Object The authors report the evolution of linear accelerator (LINAC)–based radiosurgery in the treatment of patients with intracranial meningiomas. They describe the technical aspects as well as clinical and radiological outcomes. Methods The authors performed a retrospective review of 161 patients harboring 194 intracranial meningiomas treated with various types of stereotactic irradiation at their institution between May 1991 and July 2002. Clinical and radiological follow-up data (mean follow-up period 32.5 months, range 6–125 months) were obtained in 128 patients (79.5%) with 156 meningiomas (80.4%). There were 88 women and 40 men whose mean age was 57.2 years (range 18–87 years). Stereotactic irradiation was the primary treatment in 44 patients, and 84 patients underwent resection prior to radiosurgery. Stereotactic radiosurgery (SRS) was used to treat 79 lesions and fractionated stereotactic radiotherapy (SRT) was used to treat 77. The mean dose for SRS was 1567 cGy (range 1200–2285 cGy) prescribed to a mean isodose line of 66.6% (range 50–90%). Stereotactic radiotherapy was delivered using a mean dose of 4839 cGy (range 2380–5400 cGy), prescribed to a mean isodose line of 89% (range 50–90%). The mean follow-up periods were 40 and 24 months in SRS- and SRT-treated patients, respectively. Tumor control was achieved in 58 SRT-treated benign meningiomas (90%) and in 70 SRT-treated lesions (97.2%). In patients with atypical meningiomas a considerably poorer prognosis was seen. Clinical improvement or stabilization of symptoms was observed in the majority of patients. Symptomatic complications were limited to four patients (5%) treated with SRS and four (5.2%) treated with SRT. Conclusions Stereotactic irradiation techniques have changed the neurosurgical approach to intracranial meningiomas. Either SRS or SRT delivered as a primary treatment in selected cases of skull base lesions or as an adjuvant after conservative resection has improved the management of these complex intracranial tumors.

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