Comparison of growth patterns of acoustic neuromas with and without radiosurgery.

OBJECTIVE: To compare the natural history of acoustic neuroma growth to the reported growth rate of acoustic neuromas after radiosurgical therapy, a retrospective review and meta-analysis of the literature was performed. The retrospective review was of one hundred eleven patients (average age, 71 yr) who chose to have their acoustic neuromas managed conservatively in our institution. These patients underwent serial magnetic resonance imaging for assessment of tumor growth for an average period of 38 months. Growth patterns if these untreated tumors were compared to that of radiosurgically treated acoustic neuromas reported in the literature. DATA SOURCES: The English-language literature on the topic was searched systematically by Medline and Pubmed using the following key words: acoustic neuroma, vestibular schwannoma, conservative management, conservative treatment, nonsurgical, age, elderly, growth, observation, untreated, radio-surgery, gamma knife, 13 Gy and 12 Gy. There were no limits to the year of publication. STUDY SELECTION: Articles that fulfilled inclusion criteria (methods) were studied in detail. DATA EXTRACTION: All the articles described in the study selection were used in the review.
CONCLUSION: The average growth rate of the untreated tumors was 0.7 +/- 1.4 mm/yr. Eighty-two percent grew less than 1 mm/yr, whereas 18% grew equal to or more than 1 mm/yr. Thirteen percent grew more than 2 mm/yr, with growth being noted at an average of 2.2 years after diagnosis. This represents an 87% control rate if tumor control rate is defined as less than 2-mm growth/yr. Meta-analysis indicates that tumor control rates range in the radiosurgical literature from 86% to 100%. The mean follow-up periods in the radiosurgical literature are generally not reported. Tumor control is not uniformly defined. Based on the results of this study, there is no discernable significant difference between growth patterns of untreated acoustic neuromas and those treated radiosurgically. To establish a significant difference, longer-term follow-up studies with larger sample sizes and tumor control rates are needed. Tumor control should be defined as zero growth.