Stereotactic radiotherapy for the treatment of acoustic neuromas.
ABSTRACT The authors sought to assess the safety and efficacy of stereotactic radiotherapy when using a linear accelerator equipped with a micromultileaf collimator for the treatment of patients with acoustic neuromas.
Fifty patients harboring acoustic neuromas were treated with stereotactic radiotherapy between September 1997 and June 2003. Two patients were lost to follow-up review. Patient age ranged from 20 to 76 years (median 59 years), and none had neurofibromatosis. Forty-two patients had useful hearing prior to stereotactic radiotherapy. The fifth and seventh cranial nerve functions were normal in 44 and 46 patients, respectively. Tumor volume ranged from 0.3 to 19.25 ml (median 2.51 ml). The largest tumor dimension varied from 0.6 to 4 cm (median 2.2 cm). Treatment planning in all patients included computerized tomography and magnetic resonance image fusion and beam shaping by using a micromultileaf collimator. The planning target volume included the contrast-enhancing tumor mass and a margin of normal tissue varying from 1 to 3 mm (median 2 mm). All tumors were treated with 6-MV photons and received 54 Gy prescribed at the 90% isodose line encompassing the planning target volume. A sustained increase greater than 2 mm in any tumor dimension was defined as local relapse. The follow-up duration varied from 6 to 74 months (median 36 months). The local tumor control rate in the 48 patients available for follow up was 100%. Central tumor hypodensity occurred in 32 patients (67%) at a median of 6 months following stereotactic radiotherapy. In 12 patients (25%), tumor size increased 1 to 2 mm at a median of 6 months following stereotactic radiotherapy. Increased tumor size in six of these patients was transient. In 13 patients (27%), tumor size decreased 1 to 14 mm at a median of 6 months after treatment. Useful hearing was preserved in 39 patients (93%). New facial numbness occurred in one patient (2.2%) with normal fifth cranial nerve function prior to stereotactic radiotherapy. New facial palsy occurred in one patient (2.1 %) with normal seventh cranial nerve function prior to treatment. No patient's pretreatment dysfunction of the fifth or seventh cranial nerve worsened after stereotactic radiotherapy. Tinnitus improved in six patients and worsened in two.
Stereotactic radiotherapy using field shaping for the treatment of acoustic neuromas achieves high rates of tumor control and preservation of useful hearing. The technique produces low rates of damage to the fifth and seventh cranial nerves. Long-term follow-up studies are necessary to confirm these findings.
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ABSTRACT: Vestibular schwannomas are the most common tumors of the cerebellopontine angle. Multiple management paradigms exist for patients with these benign tumors, including observation, microsurgery, stereotactic radiosurgery, and fractionated radiation therapy, or some combination of these. While the proper course of management is controversial, the goals of therapy are to achieve excellent local tumor control and optimize functional outcomes with as little treatment-related morbidity as possible. Decision-making is tailored to patient-specific factors such as tumor size, clinical presentation, patient age, and goals of hearing preservation. We review the literature in order to summarize the application of fractionated radiation therapy to this tumor entity, where it is used as a primary treatment or, more commonly, as an adjunct therapy. We also provide an overview of the use of fractionated radiation therapy for the preservation of hearing and facial function, and dosing and other technical considerations, in light of the indolent natural history of vestibular schwannomas. We also discuss potential risks associated with this treatment modality, including its effects on temporal bone structures and cranial nerves among other possible complications. Lastly, we outline future directions in this rapidly evolving segment of vestibular schwannoma therapy, which has benefited from the advent of intensity-modulated radiation therapy coupled with stereotactic localization.Journal of Clinical Neuroscience 12/2013; · 1.32 Impact Factor
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ABSTRACT: Objectives Local tumor control after radiation of vestibular schwannomas (VS) is assessed by follow-up magnetic resonance imaging (MRI) of the brain. Transient increases in tumor volume on MRI due to radiation can mimic tumor progression but are related to radiation treatment effects known as “pseudoprogression”. Our study aims to determine the presence and impact of pseudoprogression in VS patients treated with fractionated stereotactic radiotherapy. Methods We analyzed 18 patients with VS treated with fractionated radiotherapy with at least 24 months of follow-up with T1-weighted gadolinium-enhanced MRIs. Mean follow-up time was 42 months. Pre- and post-treatment tumor volumes were calculated using OsiriX® software. Events were defined as volume changes ≥10 %. Results Tumor control rate was 94 %. Forty-four percent of tumors demonstrated increases in volume on follow-up, but all but one patient had transient increases in volume with subsequent regression. Mean tumor volume increased by 35 % with the average time to regression of 24 months. Adverse side effects were more frequent in patients demonstrating pseudoprogression. There were no differences in outcomes based on pre-treatment tumor size or cystic-type versus solid-type tumors. Conclusions Fractionated stereotactic radiation therapy is an effective treatment for VS. Follow-up imaging with T1-weighted gadolinium-enhanced MRI demonstrated pseudoprogression in a third of patients occurring up to 36 months post-treatment before regression. Therefore, repeat imaging and clinical follow-up of VS should be done to rule out pseudoprogression and avoid unnecessary salvage treatment.Journal of Radiation Oncology. 03/2012; 2(1).