Prognosis of oligodendroglial tumor with ring enhancement showing central necrotic portion

Oligodendroglial tumors sometimes show heterogeneous ring enhancement with a central necrotic portion. We aimed to reveal the prognosis of such tumors based on such radiologic findings and compare them to other prognostic factors. Participants were 32 patients with oligodendroglioma (17 oligodendrogliomas, 15 anaplastic oligodendrogliomas) who underwent surgery from 2004 to 2008. We investigated tumor radiologic findings, locations, calcification, whether localized or diffuse type, and enhancement patterns. Of other prognostic factors, we analyzed age, sex, pathology, extent of removal, adjuvant therapy, genetic change in 1p and 19q, and MGMT methylation status. We checked for genetic abnormality in 1p and 19q using the FISH method. To investigate MGMT methylation, we performed methylation-specific PCR (MSP). Mean follow-up duration was 3.2 years. Median age was 42.4 years, and the male:female ratio was 21:11. Out of 17 oligodendrogliomas, 14 (82.4%) showed combined 1p/19q deletion, and 14 (82.4%), methylated MGMT. Among 15 anaplastic oligodendrogliomas, there were 7 (46.6%) with combined 1p/19q deletion and 11 (73.3%) with methylated MGMT. The 4-year recurrence-free survival and overall survival were 77.6 and 100% in oligodendrogliomas and 59.1 and 71.6% in anaplastic oligodendrogliomas, respectively. On univariate analysis, radiologic variable of ring enhancement pattern was statistically significant related with recurrence-free survival (P = 0.003). Variables such as sex (P = 0.03), combined 1p/19q loss (P = 0.04), tumor location (P = 0.02), and anaplastic pathology (P = 0.04) were significantly correlated with overall survival. Cox's regression model revealed that ring enhancement pattern was associated with frequent recurrence (ring enhancement, hazard ratio = 8.281, P = 0.04), and these showed 1p deletion only. Anaplastic oligodendrogliomas with ring enhancement like glioblastomas and without combined 1p/19q loss should receive close follow-up after treatment because of frequent recurrences.