In 9p non-deleted oligodendrogliomas, p16 hyperexpression correlated with a shorter OS (p = 0.02 in OII and p = 0.0001 in OIII) whereas lack of p16 expression was correlated to a shorter EFS and OS in 9p deleted OIII (p = 0.001 and p = 0.0002 respectively).
Combined loss of 1p and 19q was found in 38 of 56 (67.9%) and exhibited distinct concomitant deletion (P = 0.000). p53 overexpression was observed in 17 cases (30.3%), GFAP expression in 18 cases (32.1%), and p16 loss in 40 cases (74%) of oligodendrogliomas.
Our data suggest that in classic oligodendrogliomas: 1) 1p/19q tumor status is a powerful predictor of patient survival, even after recurrence; 2) p16 deletions are common progression-associated alterations; and 3) 10q deletions and EGFR amplifications are sufficiently rare to suggest the possibility of alternate diagnoses.