Evaluation of cell proliferation, epidermal growth factor receptor, and bcl-2 immunoexpression as prognostic factors for patients with World Health Organization Grade 2 oligodendroglioma

BACKGROUND. Prognostic factors in oligodendrogliomas are an area of controversy in neuropathology. Although grading and the study of some morphologic variables may be of value as prognostic parameters, the variability of postoperative disease free survival in patients with World Health Organization Grade 2 oligodendroglioma indicates that the biologic behavior of this entity remains unknown. The objective of the current study was to evaluate immunoexpression of the proliferation index (PI), epidermal growth factor receptor (EGFR), and bcl-2 as prognostic factors in patients with Grade 2 oligodendroglioma. METHODS, In a series of 19 cases of pure Grade 2 oligodendroglioma, we assessed the mitotic count, labeling index For MIB-1 and PCNA, and immunoreactivity for EGFR and bcl-2 with semiquantitative parameters and compared these with postoperative disease free survival. Statistical analyses using the Cox-Mantel nonparametric test and Spearman correlation coefficient were used to evaluate the data. RESULTS. Disease free survival was significantly shorter when the MIB-1 PI was > 5% (P = 0.0096) and the PCNA PI was > 9% (P = 0.00011) and when mitoses were observed (P = 0.00004). The paired variables also were found to correlate: MIB-1 versus PCNA (P = 0.04), MIB-1 versus mitotic count (P = 0.0184), and PCNA versus mitotic count (P = 0.0079). In all cases, there was immunoreactivity for EGFR; conversely, all cases were negative for bcl-2 in the cells with an oligodendrocyte phenotype. CONCLUSIONS. The PI was found to correlate with the postoperative disease free survival in patients with Grade 2 oligodendroglioma; therefore, the authors suggest a possible subdivision of Grade 2 oligodendrogliomas into two groups based on the mitotic count and PI. (C) 2000 American Cancer Society.