Growth of Vestibular Schwannoma during “Wait and Scan”

Introduction: In recent years more and more patients with VS have been allocated to “wait and scan” as a consequence of the understanding that not all VS grow. The aim of this study is to describe and analyze the growth of these tumors.

Subjects and Methods: Since 1976, 1446 new cases of VS have been registered prospectively with special focus on the date of diagnosis, the localization, the size of the tumor, the treatment strategy, and the results of the annual MR scanning examination.

Results: During the period a total of 517 patients were allocated to the wait and scan group. The median observation time was 3 years (range: 1-21 yrs). At the last MR scanning, the tumor had grown significantly in 72 patients, in most of the cases during the first 4 years. One hundred seventy-eight of the tumors were purely intrameatal at the time of diagnosis. Of these, 17% had increased to extrameatal extension during the observation period, in almost all cases within the first 4 years of observation. Of the tumors with extrameatal involvement at the time of diagnosis, 35% had increased significantly in size (more than 3 mm) during the period. Also in these tumors the growth occurred within the first 4 to 5 years.

Conclusion: In this material only 14% of the intrameatal and 29% of the tumors extending extrameatally showed significant growth, and in almost all cases within the first 4 to 5 years after the diagnosis. This indicates that in the wait and scan group, MR scanning controls should be performed yearly during the first 5 years; thereafter probably only occasional MR scanning is necessary.