Proliferation (MIB-1 expression) in oligodendrogliomas: assessment of quantitative methods and prognostic significance.

Expression of to nuclear antigen Ki-67 (MIB-1) has been linked to proliferative activity and prognosis in a variety of tumors. The authors assessed three techniques for quantitating MIB-1 (expression in oligodendrogliomas, correlating results with mitotic activity and prognosis. Formalin-fixed, paraffin-embedded sections of 38 oligodendrogliomas were immunostained using monoclonal MIB-l. Proliferation index (PI) was quantitated by visual estimation, CAS-200, and AC1S image analysis. MIB-1 expression and mitotic count were correlated with overall survival and recurrence (disease-free survival), defined clinically and radiographically as new tumor growth. Mean follow-up was 54 months (range 1-276). Mean PI quantitated by the three methods was statistically similar (Visual 10.5%, CAS-200, 12.2%, CAIS 11.2%). PI results by all three techniques correlated significantly with each other; visual and CAS-200 PI correlated with mitotic index. Overall and disease-free survivals were similar for patients with PIs above and below the mean by both image cytometric assays; visually estimated PIs below the mean, versus above the mean, correlated with improved disease-free survival. The authors show a significant correlation between MIB-1 PI using the visual method and recurrence in patients with oligodendrogliomas. The objectivity and speed of the image analysis systems make them an attractive alternative to visual estimation, and larger series should be analyzed for prognostic value.