LGG-01. PROGNOSTIC UTILITY AND CHARACTERISTICS OF MIB-1 LABELING INDEX AS A PROLIFERATIVE ACTIVITY MARKER IN CHILDHOOD LOW-GRADE GLIOMA: A RETROSPECTIVE OBSERVATIONAL STUDY

Abstract

Abstract BACKGROUND The prognostic utility of MIB-1 labeling index (LI) in pediatric low-grade glioma (PLGG) has not yet conclusively been described. We assess the correlation of MIB-1 LI and tumor growth velocity, aiming to contribute to the understanding of clinical implications and the predictive value of MIB-1 LI as an indicator of proliferative activity and progression-free survival (PFS) in pediatric low-grade glioma. METHODS MIB-1 LI of a cohort of 172 pediatric low-grade gliomas were comprehensively characterized. Correlation to tumor growth velocity, assessed by sequential MRI-based three-dimensional volumetric analyses, and PFS was analyzed. RESULTS Mean MIB-1 LI accounted for 2.7 % (range: <1 – 10) and showed a significant decrease to 1.5 % at secondary surgery (p =.0013). A significant difference of MIB-1 LI in different histopathological types and a correlation to tumor volume at diagnosis could be shown. Linear regression analysis showed a correlation between MIB-1 LI and preoperative TGV (R² =.55, p <.0001), while correlation to tumor growth velocity remarkably decreased after incomplete resection (R² =.08, p =.013). Log-rank test showed no impact of MIB-1 LI on 5-year PFS after incomplete (MIB-1 LI > 1 vs ≤ 1%: 48 vs 46 %, p =.73) and gross-total resection (MIB-1 LI > 1 vs ≤ 1%: 89 vs 95 %, p =.75). CONCLUSIONS This data confirms a correlation of MIB-1 LI and radiologically detectable tumor growth velocity in PLGG for the first time. Compared to preoperative tumor growth rates, a crucially decreasing correlation of MIB-1 LI and tumor growth velocity after surgery may result in limited prognostic capability of MIB-1 LI in pediatric low-grade glioma.