What is the optimal postoperative magnetic resonance imaging (MRI) schedule and length of follow-up for patients undergoing microsurgical excision of vestibular schwannoma (VS)?
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The current recommended MRI surveillance schedule after micro-surgery for VS includes MRIs at one, five, and 10 years postoperatively. Nonparametric survival analysis suggests that a majority of radiologic progression events occur in the first 10 years postoperatively.
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September 2017Background: Postoperative imaging surveillance after microsurgery for VS is performed routinely by neurotologists to screen patients for growth of residual or recurrent tumor. Nodular enhancement on postoperative gadolinium-enhanced MRI within the confines of the preoperative tumor margin is a possible indication of tumor residua/recurrence, but it is not definitive. Thus, serial imaging in cases with nodular enhancement on MRI is essential to determine whether residual tumor is present and growing. However, recommendations for the timing and frequency of MRI for VS surveillance after treatment have not been standardized.
Study design: Retrospective review of 220 patients who underwent microsurgical excision of VS at a single tertiary care center between January 1993 and March 2004.
Setting: House Clinic, Los Angeles; University of California Irvine.
Synopsis: Progression was defined as a transition to a more advanced MRI grade from a less advanced MRI grade. Of the 216 subjects with non-neurofibromatosis type 2 (NF2) cases excluded, all patients solely had VS, with the exception of three who had concomitant trigeminal schwannoma and one who had concomitant facial schwannoma. Progression occurred in eight patients of the non-NF2 cohort, none of who had a concomitant second tumor or prior radiation. Of the eight patients, two were subtotal resections and had early postoperative progression. Radiologic progression was statistically significantly different between non-NF2 and NF2 groups. Subtotal resections were statistically significantly more likely to show progression than gross total resections or near total resections. All models estimate a similar 96% progression-free survival at 10 years. The first recommended MRI is at one year postoperatively. If the MRI is clean or linear, MRIs are recommended at five and 10 years postoperatively. If MRI results are nodular, MRIs should be conducted yearly until stable. Limitations include possible errors of omission in radiologic MRI reports, inconsistent follow-up, and a small number of progression events.
Citation: Miller ME, Lin H, Mastrodimos B, Cueva RA. Long-term MRI surveillance after microsurgery for vestibular schwannoma. Laryngoscope. 2017;127:2132–2138.