Ki-67 labeling index predicts tumor progression patterns and survival in patients with atypical meningiomas following stereotactic radiosurgery

Abstract

Purpose: This study investigated whether Ki-67 labeling index (LI) correlated with clinical outcomes after SRS for atypical meningiomas.

Methods: This retrospective study examined 39 patients with atypical meningiomas who underwent SRS over a 10-year study period. Ki-67 LI was categorized into 3 groups: low (< 5%), intermediate (5%-10%), and high (> 10%). Local tumor control rates (LCRs), progression-free rates (PFRs), disease-specific survival (DSS) rates, and adverse radiation-induced events (AREs) were evaluated.

Results: The median follow-up periods were 26 months. SRS was performed at a median prescription dose of 18 Gy for tumors with a median Ki-67 LI of 9.6%. The 3-year LCRs were 100%, 74%, and 25% in the low, intermediate, and high LI groups, respectively (p = 0.011). The 3-year PFRs were 100%, 40%, and 0% in the low, intermediate, and high LI groups (p = 0.003). The 5-year DSS rates were 100%, 89%, and 50% in the low, intermediate, and high LI groups (p = 0.019). Multivariable Cox proportional hazard analysis showed a significant correlation of high LI with lower LCR (hazard ratio [HR], 3.92; 95% confidence interval [CI] 1.18-13.04, p = 0.026), lower PFR (HR 3.80; 95% CI 1.46-9.88, p = 0.006), and shorter DSS (HR 6.55; 95% CI 1.19-35.95, p = 0.031) compared with intermediate LI. The ARE rates were minimal (8%) in the entire group.

Conclusion: Patients with high Ki-67 LI showed significantly more tumor progression and tumor-related death. Ki-67 LI might offer valuable predictive insights for the post-SRS management of atypical meningiomas.

Keywords: Atypical meningioma; Ki-67 labeling index; Recurrence pattern; Stereotactic radiosurgery.

Fig. 1

Demonstrative cases representing intrafield recurrence, marginal recurrence, and remote recurrence. A, B “Intrafield recurrence” was defined as a > 10% increase in volume inside the 50% isodose line. C, D “Marginal recurrence” was defined as new tumor progression between 50 and 20% isodose lines. E, F “Remote recurrence,” defined as new tumor progression outside the 20% isodose line, was also collected. Yellow lines indicate 50% isodose, and green lines indicate 20% isodose

Fig. 2

Kaplan–Meier curves for: A, B local tumor control rates for the entire cohort and compared between three groups stratified by a Ki-67 labeling index of < 5%, 5%–10%, and > 10%, C, D progression-free rates for the entire cohort and compared between three groups stratified by a Ki-67 labeling index of < 5%, 5%–10%, and > 10%, E, F disease-specific survival rates for the entire cohort and compared between three groups stratified with a Ki-67 labeling index of < 5%, 5%–10%, and > 10%