Adaptation Of The Gamma Knife Treatment For Vestibular Schwannoma After Surgical Removal

Kazutaka Yatsushiro1, Yoshinari Shinsato2, Katsumi Nakamura3, Kazunori Arita2

1Kagoshima city, Japan 2Kagoshima University Hospital 3 Fujimoto-Hayasuzu Hospital

Keywords: vestibular schwannoma, resection, gamma knife, technique, radiosurgery

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     When we perform subtotal or total removal of the vestibular schwannoma, recurrence was found rarely. However, in some cases recurrence was detected after removal of the tumor in several years.
     The purpose of this study is to clarify the recurrence factor after the surgical procedure for vestibular schwannoma and to assess adaptation of the gamma knife treatment for its residual tumor.
     Between January 1999 and December 2005, 33 eligible patients with vestibular schwannoma were enrolled in this study.
     All the patients were performed surgical removal with the suboccipital retromastoid approach and were followed up by MRI every 6 – 12 months for 50.6 (11.1 – 98.5) months. We evaluated volume of residual tumors, MIB-1 index, age, sex as recurrence factors.
     Tumor regrowth was founded in 6 cases after 36.4 (17 – 47) month removal of the tumor. Although partial removal of the tumor was performed in 3 cases with recurrence, in the other 3 cases the tumor was removed subtotally. Residual tumor volume was 419.3 and 101.8 mm3 in recurrence and in not – recurrence cases, respectively (P = 0.041). MIB-1 index of all recurrence cases was more than 3.0 %. The average of MIB-1 index was 4.4 % and 1.0 % in recurrence and in not – recurrence cases, respectively (P = 0.003).
     This is a retrospective study.
      Large residual tumor volume and high MIB-1 index were important recurrence factors in vestibular schwannoma after the surgical procedure.
     In a case to meet these conditions, it is recommended that gamma knife treatment is provided early after surgical removal.


Project Roles:

K. Yatsushiro (), Y. Shinsato (), K. Nakamura (), K. Arita ()