Diagnostic and prognostic roles of loss of CIC protein expression in oligodendroglial tumors

Abstract

Objective: To investigate the usefulness of loss of CIC expression as the prescreening detection of 1p/19q co-deletion in the diagnosis of oligodendroglial tumors and its prognostic implication. Methods: The retrospective study included 113 oligodendroglial tumors diagnosed in the Department of Pathology, Xuanwu Hospital, Capital Medical University. Expression of CIC protein was detected by immunohistochemistry, and the 1p/19q co-deletion by fluorescence in situ hybridization in all the tumors; and the correlation of the loss of protein and 1p/19q co-deletion with prognosis was assessed. Results: The rate of negative CIC protein expression was 59.3% (67/113) in 113 oligodendroglial tumors. CIC protein expression was differentially lost in various gliomas, 85.7% (42/49) in pure oligodendrogliomas and 39.1% (25/64) in mixed oligodendroglial tumors (P<0.01). The loss of CIC protein expression showed a sensitivity of 76.1% (54/71), specificity 71.1% (27/38), false positive rate of 16.9% (11/65), and a false negative rate of 38.6% (17/44). In 63 cases integrated diagnosis as oligodendroglial tumors with mutant IDH and 1p/19q co-deletion, the loss of CIC protein expression was 81.0% (51/63); the sensitivity and specificity were increased to 81.0% (51/63) and 76.9% (20/26), and the false positive rate and false negative rate decreased to 10.5% (6/57) and 37.5% (12/32), respectively. By using Kaplan-Meier analysis, the CIC negative group showed a trend towards better outcome than the CIC positive group, but there was no statistical difference (overall survival: P=0.218; progression free survival: P=0.249). Conclusions: Detection of the lost CIC protein expression can predict the chromosome 1p/19q co-deletion. In oligodendroglial tumors with IDH mutant and 1p/19q co-deletion, there is no relation between prognosis and CIC protein expression.