Acoustic Neuroma: Potential Benefits of Fractionated Stereotactic Radiosurgery

Abstract

Background: Single-fraction radiosurgery of acoustic neuromas less than 3 cm in diameter is remarkable for high control but not infrequent incidence of facial and trigeminal neuropathy. Larger tumors treated surgically often result in deafness and facial neuropathy. Fractionated stereotactic radiosurgery was used in an effort to maintain effective therapy while minimizing toxicity of treatment. Methods: The authors described 38 patients with acoustic neuromas, with age range 35-89 years (mean, 60 years). 2,000 cGy in divided weekly doses of 400 or 500 cGy was most commonly prescribed. Tumors ≧3 cm (n = 16) received the 5 fraction schema. Mean tumor volume was 6.9 cm³, with range from 0.1 to 32.0 cm³. Results: Median clinical follow-up was 27.1 months, while neuroimaging follow-up had a median of 16.3 months. All tumors were controlled. Of 23 tumors smaller than 3 cm, 14 (61%) decreased in size, and 9 showed cessation of growth. Thirteen of 16 (81%) large acoustic neuromas (3-5 cm) diminished in size. The remaining 3 showed cessation of growth. Median radiographic follow-up was 20 months, with a median clinical follow-up of 28 months. No patient developed fifth nerve symptoms after treatment nor did any patient require surgery for treatment failure. Only one had temporary seventh nerve palsy. Conclusion: Fractionated stereotactic radiosurgery offers a therapeutic approach producing high control rates while avoiding morbidity frequently seen after single-fraction radiosurgery or microsurgery.

Multisession stereotactic radiosurgery for large vestibular schwannomas

“…4,14,16,22,32,45 In a recent publication, Yang et al concluded that if the patient is asymptomatic, the tumor is smaller than 10 cm 3 , and/or the Koos grade is less than 4, SRS could be the first choice of treatment more likely to lead to tumor regression. 45 A similar conclusion was presented by van de Langenberg et al 39 in the first part of a recent study: radiological growth control was achieved in nearly 90% of cases in both series.…”

“…Nevertheless, despite the radiobiological expectations based on a/b calculations, excellent results have been obtained also by fractionated SRS and fractionated stereotactic radiotherapy (50-55 Gy in 25-30 fractions) for VS, with control rates of 90%-95%. 5,11,18,22,23,25,27,29,44 In light of these seemingly paradoxical data, we made a comparison between the conventionaldose SRS and the dose of multisession SRS in our series.…”

“…This is a generally accepted criterion, 14,22,24,27,30,45 even though stability of tumors that may present after long periods of quiescence can be a misleading appearance of success. A 1-mm-diameter change results in a volume difference of about 10%.…”

Fractionated Stereotactic Radiotherapy for Acoustic Neuromas

“…Andrews et al [28] showed preservation of the facial nerve in 49 of 50 patients receiving FSR. Lederman et al [31] showed that only 1 of 38 patients treated with 2,000 cGy in four or five fractions had temporary seventh-nerve palsy. Adler et al [32] noted facial neuropathy in 1 patient and trigeminal neuropathy in 5 of 31 patients who received 21 Gy in three fractions during 1 day.…”

Radiosurgery for glomus jugulare: history and recent progress

“…43 Groups have reported very low rates of cranial nerve deficits in treating vestibular schwannomas with fractionated radiosurgery. 20,27,47 In similar fashion, Henzel et al 13 treated 17 patients who had glomus jugulare with fractionated LINAC radiosurgery, delivering small doses of radiation over ~ 30 fractions, equivalent to a single-fraction 15-to 16-Gy margin dose. All patients either improved clinically (56%) or remained stable (44%), and all tumors either decreased in size (31%) or remained unchanged (69%).…”