Proliferative activity as measured by MIB-1 labeling index and long-term outcome of visual pathway astrocytomas in children

Although most visual pathway tumors are low-grade gliomas their biologic be havior is highly unpredictable. In order to determine whether assessment of proliferative activity can assist in predicting tumor behavior, we studied the MIB-1 labeling indices (MIB-1 LIs) in surgical specimens and monitored tumor growth in 31 consecutive children operated on between 1978 and 1997. The MIB-1 LIs at diagnosis varied from 0-10.6% (mean +/- SD, 3.27 +/- 2.49 %). Tumor progression occurred in 19 patients leading to death in seven, th ree of whom had neurofibromatosis type 1 (NF1). No association between MIB- 1 LI at initial diagnosis and both progression free and overall survival wa s apparent. However, the MIB-1 LIs increased to 15.2% and 18% in two patien ts with NF1 who developed highly malignant gliomas 6 and 6.5 years after ir radiation. In the remaining patients the MIB-1 LIs did not change significa ntly over time in a total of 17 repeat surgeries. Three patients with LIs o f 6.8%, 10.6% and 8.8% are stable after 6, 4.5 and 3.5 years with partial r esection, biopsy and subtotal resection, respectively, and no further thera py in the first two and chemotherapy in the latter. Three patients (10%) wi th LIs of 6.4%, 4.8% and 2.2% either presented with or developed leptomenin geal spread during follow-up. While MIB-1 LI does not appear to assist in c linical decision making patient numbers were too small to find out whether response to chemotherapy varies with proliferative potential.