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 controv ersy in neuropathology. Although grading and the study of some morphologic variables may be of value as prognostic parameters, the variability of post operative disease free survival in patients with World Health Organization Grade 2 oligodendroglioma indicates that the biologic behavior of this enti ty remains unknown. The objective of the current study was to evaluate immu noexpression of the proliferation index (PI), epidermal growth factor recep tor (EGFR), and bcl-2 as prognostic factors in patients with Grade 2 oligod endroglioma. METHODS, In a series of 19 cases of pure Grade 2 oligodendroglioma, we asse ssed the mitotic count, labeling index For MIB-1 and PCNA, and immunoreacti vity for EGFR and bcl-2 with semiquantitative parameters and compared these with postoperative disease free survival. Statistical analyses using the C ox-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 mitos es were observed (P = 0.00004). The paired variables also were found to cor relate: MIB-1 versus PCNA (P = 0.04), MIB-1 versus mitotic count (P = 0.018 4), and PCNA versus mitotic count (P = 0.0079). In all cases, there was imm unoreactivity for EGFR; conversely, all cases were negative for bcl-2 in th e cells with an oligodendrocyte phenotype. CONCLUSIONS. The PI was found to correlate with the postoperative disease f ree survival in patients with Grade 2 oligodendroglioma; therefore, the aut hors suggest a possible subdivision of Grade 2 oligodendrogliomas into two groups based on the mitotic count and PI. (C) 2000 American Cancer Society.