Multisession stereotactic radiosurgery for large vestibular schwannomas.

OBJECT: Microsurgery is not the only option for larger vestibular schwannomas (VSs); recent reviews have confirmed the feasibility and efficacy of radiosurgery for larger VSs. This study illustrates the outcomes of a series of large VSs after multisession stereotactic radiosurgery (SRS). METHODS: A series of 33 VSs larger than 8 cm(3) (range 8-24 cm(3), mean 11 cm(3), median 9.4 cm(3)) were treated using the CyberKnife from 2003 to 2011 with the multisession SRS technique in 2-5 fractions (14-19.5 Gy). Five patients had undergone surgical removal and 5 had ventriculoperitoneal shunts. Nine patients were eligible for but refused surgery. Twelve patients were older than 70 years and 5 were younger than 40 years. Two female patients had neurofibromatosis. RESULTS: The follow-up period ranged from 12 to 111 months (median 48 months); radiological growth control was achieved in 94% of cases: 19 tumors (58%) displayed no size variation or reduction in tumor diameter; 12 (36%), after a transient enlargement, presented with arrested growth or shrinkage. Seven patients had a volume reduction of more than 50%. Two patients (6%) needed debulking and 2 were treated with ventriculoperitoneal shunts. Actuarial progressionfree survival rates at 1 year and 5 years were 97% and 83%, respectively. Hearing was retained in 7 of the 8 patients with serviceable baseline hearing. Adverse events were limited to 1 case each of vertigo, tongue paresthesia, and trigeminal neuralgia. CONCLUSIONS: The good control rate obtained with multisession SRS deepens the controversy of the radiobiology of VSs and may extend the indication of radiation therapy (fractionated or SRS) for large VSs to include patients without symptoms of mass effect. The limited number of cases and short follow-up period do not provide sufficient support for widespread application of multisession SRS in young patients. Further studies with multisession SRS are warranted.

Three-dimensional angiography for radiosurgical treatment planning for arteriovenous malformations.

OBJECT: Radiosurgical treatment of a cerebral arteriovenous malformation (AVM) requires the precise definition of the nidus of the lesion in stereotactic space. This cannot be accomplished using simple stereotactic angiography. but requires a combination of stereotactic biplanar angiographic images and stereotactic contrast-enhanced computerized tomography (CT) scans. In the present study the authors describe a method in which three-dimensional (3D) rotational angiography is integrated into stereotactic space to aid treatment planning for radiosurgery. METHODS: Twenty patients harboring AVMs underwent treatment planning prior to linear accelerator radiosurgery. Planning involved the acquisition of two different data sets, one of which was obtained using the standard method (a combination of biplanar stereotactic angiography with stereotactic CT scanning), and the other, which was procured using a new technique (nonstereotactic 3D rotational angiography combined with stereotactic CT scanning by a procedure of image fusion). The treatment plan that was developed using the new method was compared with that developed using the standard one. For each patient the number of isocenters and the dimension of selected collimators were the same, based on the information supplied in both methods. Target coordinates were modified in only five cases and by a limited amount (mean 0.7 mm, range 0.3-1 mm). CONCLUSIONS: The new imaging modality offers an easier and more immediate interpretation of 3D data, while maintaining the same accuracy in target definition as that provided by the standard technique. Moreover, the new method has the advantage of using nonstereotactic 3D angiography, which can be performed at a different site and a different time with respect to the irradiation procedure.