Prognostic Value of Ki-67 Labeling Index and Postoperative Radiotherapy in WHO Grade II Meningioma.

Objective: This study was performed to determine the clinical significance of the Ki-67 labeling index (LI) for local control (LC) in patients with World Health Organization (WHO) grade II meningioma. We also tried to discern the effect of postoperative radiotherapy (PORT) on LC depending upon the Ki-67 LI value. Materials and Methods: The medical records and values of Ki-67 LIs were retrospectively reviewed for 50 patients who underwent surgical resection of intracranial WHO grade II meningiomas at Samsung Medical Center from May 2001 to December 2012. Forty-three patients (86%) were treated with immediate PORT. The median total radiation dose was 60 Gy (range, 54 to 60 Gy). Results: The median follow-up was 47.4 months. The mean Ki-67 LI was 13% (range, 1% to 47%). Twelve patients (24.0%) showed local failure, and 8 patients (16.0%) experienced local failure even after PORT. The mean Ki-67 LI was 15% in patients with local failure (n = 12) and 12% in patients without local failure (n = 38). The 3-year actuarial LC was 80.5%. The 3-year overall survival was 89.5%. Ki-67 LI > 13% and PORT were significant prognostic factors for LC (P = 0.015 and 0.009, respectively). In patients with Ki-67 LI > 13% (n = 17), PORT (n = 14) improved LC (P < 0.001). However, PORT (n = 29) did not affect LC (P = 0.412) for patients with Ki-67 LI <= 13% (n = 33). Conclusions: Ki-67 LI can be a useful prognostic factor for LC in WHO grade II meningioma. In patients with Ki-67 LI > 13%, PORT should be recommended to improve LC.