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swelling 8 mo after delivery of 35 Gy to a volume of 73.6 mL in the parasellar region). Of 13/17 patients followed for a mean of 40 mo, none had evidence of tumor relapse. Unfortunately, "late, severe" side effects occurred in five patients (including one patient with a recurrent optic canal meningioma who became blind 5 mo after a dose of 35 Gy to the optic nerve). The authors felt that the treatment dose needed to be lowered to reduce complications, and the doses delivered in this early series are, in fact, much higher than currently recommended.

Valentino et al. (111) reported on 72 meningioma patients treated with a mean marginal dose of 37 Gy (given over one to four sessions) (Table 4). Over a mean follow-up of 48 mo, 69% of the tumors regressed and 25% remained stable in size, for a local control rate of 94%. Three patients developed transient symptoms related to increased intracranial pressure, and one additional patient was noted on follow-up imaging to have asymptomatic transient peritumoral edema.

Chang and Adler (112) reported on 55 patients who were treated with LINAC radiosurgery for cranial base meningiomas at Stanford. Mean marginal dose was 18 Gy (range 12-25). Over a mean follow-up of 48 mo, only one tumor enlarged, resulting in a 2-yr actuarial local control rate of 98%. Ten patients experienced mild transient neurologic compromise, and four patients (7%) suffered the following persistent effects. Symptomatic radiation necrosis developed in two patients, with seizures in one and right hemiparesis in the other. One patient acquired vagal and hypoglossal palsies, and another suffered a persistent facial paresis. This group has also reported their experience with 24 cavernous sinus meningiomas (113). The mean volume treated was 6. 83 cm3 (range 0.45-22.45 cm3), covered with an average of 2.3 isocenters (range 1-5). Radiation dose averaged 17.7 Gy (range 14-20 Gy). Follow-up averaged 45.6 mo (range 19-80 mo). Tumor control (stabilization) following radiosurgery was noted in 15 (63%) and tumor shrinkage in 9 (37%). Neurologic status was improved in 10 patients (42%) and unchanged in 12 patients (50%). There was one case of symptomatic brain necrosis and one case of radiation edema (asymptomatic). The 2-yr actuarial tumor control rate was 100%.

Colombo and Francescon (114) reported their series of 74 cranial base meningiomas as part of a larger report detailing their entire experience at the LINAC radiosurgery unit at Vicenza City Hospital in Italy. After treatment with a mean marginal dose of 22 Gy (range 18-26 Gy) and follow-up for a mean duration of 33 mo, the 8-yr actuarial tumor control rate was calculated to be 75%. Two patients suffered delayed visual field reduction after irradiation of lesions impinging on the optic chiasm.

Hakim et al. (115) reported results of LINAC radiosurgery for 127 meningioma patients treated by the Harvard group. Eighty-three percent of patients had previous surgery. Mean marginal dose was 15 Gy and mean follow-up duration was 31 mo. Five-year actuarial survival for the benign subgroup was 89%. Complications included two treatment-related deaths (one case of edema-induced herniation and the other death secondary to edema and hypothalamic injury), as well as one case of (expected) monocular blindness, one incidence of

Table 4

LINAC Radiosurgery for Meningiomas

Table 4

LINAC Radiosurgery for Meningiomas

Parameter

Valentino (80) Rome 1993

Chang (113) Stanford 1997

Colombo (114) Vicenza, Italy 1998)

Hakim (115) Harvard 1998

U of Florida

(116) 1998

No of patients

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